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Colorsound Power boost noise issue [message #171011] Mon, 24 July 2017 06:28 Go to next message
messages@element14.co
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Registered: March 2013
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A while ago I posted regarding transistors etc for a Colorsound Power boost clone pedal I was working on. Well, after many months I've actually finished 2 of them... They are identical to an original right down to the size of the PCB.and the components used. There is one slight difference in so far as the first board was a direct print from an Eagle layout, the second board was a 121 trace of an original PCB, only slightly different from the eagle board. This is the Eagle boardThis is board 2, a 121 copy of an original Colorsound Power boost PCB, and also a photo of an original The component side is like this.. mine is on the left, the genuine PCB is on the right. The pots on my board are mounted to the board like the original... Just from the other side. The reason for this is purely down to the thread length on the pots. The thread on my pots isn't long enough to go through the PCB, and then through the enclosure as well.    The schematic used was this one..... a simple circuit which is basically a pre-amp that boosts the volume and treble and bass.  The components on the first board were all brand new, where the components on the 2nd board were mostly NOS for a visual vintage vibe. I have an issue on both boards that I'm trying to troubleshoot, and currently i have reached out to 2 DIY effect pedal forums with no real resolution. i'm hoping someone here may be able to point me in the right direction, i'll try to give as much information as possible. I have a cycled ticking noise that increases in volume when you turn the volume up on the pedal. it's not affected by the guitar volume, and stays there even when you turn the guitar down. Check out this video. 
 
 
 The last video shows a slight earth problem that may or may not have anything to do with the noise. i thought i'd include it anyway. I have taken voltage readings off my pedal, and compared them to the readings from a genuine pedal (I'll say at this stage that my pedal is exactly the same as the genuine pedal as regards component values) Genuine Pedal voltagesBattery: 18.84VQ1 C 6.43V B 3.92V E 3.54VQ2 C 11.53V B 6.44V E 5.82VQ3 C 10.19V B 2.77V E 2.23V  My voltages:Battery: 18.80VQ1 C 6.37V B 3.90V E 3.52VQ2 C 11.36V B 6.37V E 5.74VQ3 C 10.54V B 2.75V E 2.19V
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Original article at https://www.element14.com/community/message/225958?tstart=0#225958
Re: Colorsound Power boost noise issue [message #171012 is a reply to message #171011] Mon, 24 July 2017 06:57 Go to previous messageGo to next message
messages@element14.co
Messages: 565
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Hi Andy,You are getting an oscillation that could come from a number of sources. Here is what I observed as differences between the original and the newer units. By mounting the controls on the opposite side you are loosing the shielding that would have been provided by the metal control housings. In the original the treble at least was grounded on the circuit board.  I would tie the metal control housings together and then to a good common ground. Notice how the original control has the input and output lines carefully run down the sides and away from each other. You might even try putting the input lines in coax to help minimizing the chance that they can couple with the output wires. It isn't obvious why the original switch and your switch are different. The difference may be bringing the input and output lines too close together and letting them couple by capacitance. Instead of tying the grounds together on the input and output jacks you might try tying them together on the ground of the circuit board. Hopefully this will give you some experiments to try out. If it doesn't lead to a solution come back and I will try to think of some more.John
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Original article at https://www.element14.com/community/message/225922?tstart=0#225922
Re: Colorsound Power boost noise issue [message #171014 is a reply to message #171011] Mon, 24 July 2017 10:25 Go to previous messageGo to next message
messages@element14.co
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Hi John, thanks for your reply. I'm off to sunny Yorkshire today until Friday, but will check the groundings at the weekend and report back.... In a nutshell, you suspect it's a ground issue?
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Original article at https://www.element14.com/community/message/225959?tstart=0#225959
Re: Colorsound Power boost noise issue [message #171021 is a reply to message #171011] Mon, 24 July 2017 23:16 Go to previous messageGo to next message
messages@element14.co
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Hi Andy, I would start with the simple things like position of the signal wires. Next I would bring all the ground wires to a common point on the circuit board and eliminate loops and strings. Finally I would look at the proximity of things on the switch to see if that is where the problem comes from. Your noticing that the switch has some hum to it may be the unit trying to tell you something.John
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Original article at https://www.element14.com/community/message/226016?tstart=0#226016
Re: Colorsound Power boost noise issue [message #171040 is a reply to message #171011] Thu, 27 July 2017 07:50 Go to previous messageGo to next message
messages@element14.co
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Hi John, OK, this is what I'll try.  I'll solder some wire between the 3 pots, connecting them together in a string then finally connect the last one to the ground of the board. I'll do the same with each jack socket. This will mean simply drilling 2 or 3 extra holes in the board. I'll try my best to separate the wiring, and channel it around the edge of the enclosure. I'll take plenty of pictures so you can see exactly what I've done. Andy
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Original article at https://www.element14.com/community/message/226151?tstart=0#226151
Re: Colorsound Power boost noise issue [message #171041 is a reply to message #171011] Thu, 27 July 2017 12:27 Go to previous messageGo to next message
messages@element14.co
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Hi Andy,That sounds good. One other suggestion, lets have a 1000uF 25 volt capacitor that we can put on the board from the 18 V plus to the Ground. The length of the power wires up to the AC adapter jack and back to the board could be causing the power to pulse at higher volume. John
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Original article at https://www.element14.com/community/message/226167?tstart=0#226167
Re: Colorsound Power boost noise issue [message #171045 is a reply to message #171011] Fri, 28 July 2017 06:49 Go to previous messageGo to next message
messages@element14.co
Messages: 565
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I'm not 100% convinced that the DC power lines are an issue as this problem occurs using both DC power and batteries. Here is a gut shot of a reissue power boost with an LED, and a DC power socket. This also has a master volume installed solasound 18v power boost The difference between the 2 switches is because of the inclusion of the LED. You need the extra pole for the LED.I think this is purely a  shielding/grounding issue as you pointed out initially.
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Original article at https://www.element14.com/community/message/226144?tstart=0#226144
Re: Colorsound Power boost noise issue [message #171048 is a reply to message #171011] Fri, 28 July 2017 13:05 Go to previous messageGo to next message
messages@element14.co
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Hi Andy,I just noticed that the original case and the new case are made of metal and your replica is made of plastic. The metal could have a shielding effect that the plastic doesn't give you. I hope the extra ground wires and the separation of the signal in and out wires solves the problem. Keep in mind there are a few possibilities and I may have missed on my guesses.John
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Original article at https://www.element14.com/community/message/226149?tstart=0#226149
Re: Colorsound Power boost noise issue [message #171058 is a reply to message #171011] Sat, 29 July 2017 08:02 Go to previous messageGo to next message
messages@element14.co
Messages: 565
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Hi John, My case isn't plastic, it's a Hammond enclosure made of aluminium. You are correct the original cases were made of pressed steel. UPDATE:I have removed the board from the enclosure, and removed all the wires from the board. I'll now start a process of elimination.... first of all I'll tidy up all the wiring with new wires and ground the jack sockets to the board, and then test the board as it is, and post a video.... coming soon
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Original article at https://www.element14.com/community/message/226231?tstart=0#226231
Re: Colorsound Power boost noise issue [message #171059 is a reply to message #171011] Sat, 29 July 2017 12:18 Go to previous messageGo to next message
messages@element14.co
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Ok guys, here's the latest update. I've removed the board from the enclosure, and the noise is still there. It's been wired as basically as possible. I've wired the treble pot to the ground on the board, as the original pedal had the treble pot grounded directly to the board via the body of the pot. I've checked a triple checked all soldering on the board and there are no solder bridges that I can see.I'm beginning to think it's the board, and maybe during my design phase I did something wrong somewhere. Anyway, here's the latest video, i think I need to get this sorted before I stuff it into an enclosure. 

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Original article at https://www.element14.com/community/message/226233?tstart=0#226233
Re: Colorsound Power boost noise issue [message #171060 is a reply to message #171011] Sat, 29 July 2017 13:14 Go to previous messageGo to next message
messages@element14.co
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Hi Andy, It is a high gain circuit, perhaps some component values were misread (e.g. red instead of brown) on the resistors? In the photos, some colours look brown on the original, but red on the replica. But it could be lighting conditions.It would be worth confirming with a multimeter. As I understand it is an amp with tone controls. According to the video, it is functioning fine when the volume control on it is set low. At that low setting, is the output comparable to the original amp, at the same setting, or at a higher setting? Due to the long wiring, perhaps there is some instability due to the very high gain as that control is turned.
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Original article at https://www.element14.com/community/message/226203?tstart=0#226203
Re: Colorsound Power boost noise issue [message #171061 is a reply to message #171011] Sat, 29 July 2017 13:22 Go to previous messageGo to next message
messages@element14.co
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Hi Shabaz, I can understand your query regarding the resistors values, but the values were taken off the schematic, and confirmed by comparison with the following images. one of these images was taken from a boost pedal that is owned by a forum member over at www.freestompboxes.org. The other is a stock image from the internet. The schematic was drawn by the forum member (Electric Warrior) The values were confirmed via a thread on that forum last year. Here's a link to the thread on the forum, freestompboxes.org • View topic - Colorsound Power Boost 18v    
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Original article at https://www.element14.com/community/message/226234?tstart=0#226234
Re: Colorsound Power boost noise issue [message #171062 is a reply to message #171011] Sat, 29 July 2017 13:38 Go to previous messageGo to next message
messages@element14.co
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Hi Andy, I see.. One other thing that could be worth doing (since your circuit appears to work when the gain is set to the lowest setting) is to swap out the 22uF capacitor at the bottom-left of the circuit diagram (i.e. the one connected to the volume pot) and change it to (say) 10uF, and if that doesn't help, also swap out the 4.7uF capacitor at the bottom-right side (the one in parallel with the 1k resistor) and replace that with 2.2uF.The old capacitors may have not had the capacitance to match the value written on them, whereas modern capacitors are a bit more closer to the value printed on them. Half the capacitance could be a possibility.Also it could be worth lifting up the variable resistors slightly off the PCB, to see if a few additional mm air gap makes a difference. There could be capacitive coupling if the back of the pots is metal, and that will be reduced if the gap is increased.
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Original article at https://www.element14.com/community/message/226204?tstart=0#226204
Re: Colorsound Power boost noise issue [message #171063 is a reply to message #171011] Sat, 29 July 2017 13:43 Go to previous messageGo to next message
messages@element14.co
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Hi Andy,This is an excellent experiment that you have conducted to solve the problem. It eliminates several of the concerns that I expressed. I have gone back and examined the schematic that you posted. I am not enough of an expert to say anything specifically on this but I have never seen a volume control configured like the one in your schematic. Perhaps someone like michaelkellett can take a look at the schematic. I personally would like to understand how this configuration is controlling the volume. It obviously works fine up to the point where the oscillations start. If we can understand what is going on perhaps we can find a way to suppress the oscillation at high gain.John
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Original article at https://www.element14.com/community/message/226235?tstart=0#226235
Re: Colorsound Power boost noise issue [message #171064 is a reply to message #171011] Sat, 29 July 2017 13:54 Go to previous messageGo to next message
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Prior to the latest experiment, the pots has plastic dust covers on them that prevented them from touching the board. i have since removed the plastic covers so that i can ground the metal covers to the board.
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Original article at https://www.element14.com/community/message/226236?tstart=0#226236
Re: Colorsound Power boost noise issue [message #171065 is a reply to message #171011] Sat, 29 July 2017 14:35 Go to previous messageGo to next message
messages@element14.co
Messages: 565
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John, it's less of a volume and more of a gain potentiometer. Increasing the "volume" pushes the sound into distortion. It doesn't really happen on this little practice amp as the pedal is really intended to be used on powerful valve amps. When i plug it into my big guitar system and switch the pedal on even with the "volume" on it's lowest setting it adds around 20db boost. this is standard for this pedal..... So, think of this control as less of a volume, and more of a gain. Here is a YouTube video of a demo... it'll give you an idea of how it should perform. 

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Original article at https://www.element14.com/community/message/226237?tstart=0#226237
Re: Colorsound Power boost noise issue [message #171074 is a reply to message #171011] Sat, 29 July 2017 18:09 Go to previous messageGo to next message
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I've done a bit more tinkering, and have a few positive things to report. In DIYStompboxes a forum poster suggested I wire up a jack plug shorting the tip to ground this shorts the input to ground. This should reduce RF pickup if that is the problem. i wired up the plug and tested the board again, no cigar, still the same. There have been some changes, and I've done nothing!! 1. The noise has reduced significantly by itself, i don't know why.2. I can turn the volume of the guitar, the amp and the pedal all the way up and the noise is just audible. 3. However, when I back of the volume of the guitar all the way off, the noise increases in volume. Here's the latest video. 

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Original article at https://www.element14.com/community/message/226243?tstart=0#226243
Re: Colorsound Power boost noise issue [message #171075 is a reply to message #171011] Sat, 29 July 2017 18:21 Go to previous messageGo to next message
messages@element14.co
Messages: 565
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Hi Andy, It is likely unstable due to feedback. The long tracks, the wires, and and the large bits of metal (the pots) capacitively bridging portions of circuitry could be causing further issues. Plus the input has a high impedance (possibly more than the guitar pickup requires; I'm not knowledgeable on that though). Regardless of grounding the pot, the metalwork seems very close to different portions of the tracks. Adjusting the volume of the guitar is changing the input impedance if the guitar has a pot on the output and that could change the behaviour too. Furthermore, your gain may be too high due to your capacitors having higher capacitance than the original design; that can be solved by sizing the two capacitors mentioned earlier to be a bit smaller in value (half the value could be a good place to start).
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Original article at https://www.element14.com/community/message/226209?tstart=0#226209
Re: Colorsound Power boost noise issue [message #171076 is a reply to message #171011] Sat, 29 July 2017 18:38 Go to previous messageGo to next message
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Hi Shabaz, The feedback is to be expected with this pedal, i'd be pretty annoyed if it didn't feed back at high volume to be honest. All the capacitors, etc are as per the original design.... However, there were 2 other schematics that they used, a version 2 (mine is the version 1), and also an overdriver schematic, which was done for the US market, and ran on 9v instead of 18v. here are all the schematics 
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Original article at https://www.element14.com/community/message/226244?tstart=0#226244
Re: Colorsound Power boost noise issue [message #171078 is a reply to message #171011] Sun, 30 July 2017 02:21 Go to previous messageGo to next message
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Hi Andy,The feed back that shabaz  is referring to is the noise you are complaining about. The put put put is a form of low frequency undesirable feedback.John
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Original article at https://www.element14.com/community/message/226271?tstart=0#226271
Re: Colorsound Power boost noise issue [message #171080 is a reply to message #171011] Sun, 30 July 2017 07:03 Go to previous messageGo to next message
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Ahh, i understand. Sorry, newbie to treminology
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Original article at https://www.element14.com/community/message/226258?tstart=0#226258
Re: Colorsound Power boost noise issue [message #171083 is a reply to message #171011] Sun, 30 July 2017 10:16 Go to previous messageGo to next message
messages@element14.co
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Hello Andy, If the noise reduces when the guitar volume control is at min this suggests that it is affected by the impedance to ground at the input, and that it doesn't like low impedance, which is kind of confirmed by your results with the shorting plug. There are (at least) two ways a circuit like this can be unstable, one is where it actually self oscillates at the lowish frequency you are hearing and the other is where it self oscillates at a very high frequency (that you can't hear directly) but that the oscillation is pulsed at a low frequency. This second effect used to be called squegging but I think the term is less common now. To work out what is actually going on you need an oscilloscope - any other approach is going to be shooting in the dark - we might get lucky , and we might not. Where are you - there may be a suitably equipped E14 member who could help out. MK
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Original article at https://www.element14.com/community/message/226260?tstart=0#226260
Re: Colorsound Power boost noise issue [message #171086 is a reply to message #171011] Sun, 30 July 2017 13:43 Go to previous messageGo to next message
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Hi Michael,Thanks for your insight as I was not sure how to help Andy and I still don't understand how that volume control works but tonight the bread board and I are going to duplicate the first stage and look at it with my oscilloscope and see if I can figure it out. Unfortunately Andy and I are 6000 miles apart and my oscilloscope won't be of much help to him.John
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Original article at https://www.element14.com/community/message/226262?tstart=0#226262
Re: Colorsound Power boost noise issue [message #171088 is a reply to message #171011] Sun, 30 July 2017 14:27 Go to previous messageGo to next message
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The basic circuit of the amplifier is based on what we used to call a DC coupled pair and was widely used as the magnetic pickup pre-amplifier in HiFi designs of the 70s. Here's an article about it but it refers to the author's book , Discrete design: 2-transistor RIAA preamp  It uses separate paths for AC and DC feedback, but the Colorsound design rather obscures this in its search for distortion  and a definite sound of its own. There should be no AC signal at Q2 emitter so the 150k resistor is providing DC feedback to Q1 base. AC feedback (and some DC) comes via the 12k resistor from Q2 collector to Q1 emitter, where it is shorted out by the 22uF cap and the pot, since the pot can be adjusted to zero there is NO AC feedback at maximum gain. It should be possible to model it in LTSpice. MK
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Original article at https://www.element14.com/community/message/226287?tstart=0#226287
Re: Colorsound Power boost noise issue [message #171089 is a reply to message #171011] Sun, 30 July 2017 14:46 Go to previous messageGo to next message
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Thanks Michael for taking the time to spell it out for me. I will study the schematic and your explanation so that I better understand this design for the future. Also thanks for the link.John
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Original article at https://www.element14.com/community/message/226253?tstart=0#226253
Re: Colorsound Power boost noise issue [message #171090 is a reply to message #171011] Sun, 30 July 2017 15:15 Go to previous messageGo to next message
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It simulates OK in LTSpice, 300Hz sine wave, transient simulation, max(almost) gain Model follows: Version 4SHEET 1 2600 692WIRE 640 -256 160 -256WIRE 1888 -256 640 -256WIRE 1984 -256 1888 -256WIRE 2336 -256 1984 -256WIRE 2480 -256 2336 -256WIRE 640 -224 640 -256WIRE 160 -160 160 -256WIRE 1296 -160 1168 -160WIRE 1536 -160 1360 -160WIRE 480 -112 240 -112WIRE 640 -112 640 -144WIRE 640 -112 480 -112WIRE 1888 -96 1888 -256WIRE 1984 -96 1984 -256WIRE 480 -80 480 -112WIRE 640 -48 640 -112WIRE 768 -48 640 -48WIRE 1008 -48 832 -48WIRE 1040 -48 1008 -48WIRE 1168 -48 1168 -160WIRE 1168 -48 1120 -48WIRE 1216 -48 1168 -48WIRE 1344 -48 1296 -48WIRE 1408 -48 1344 -48WIRE 1536 -48 1536 -160WIRE 1536 -48 1488 -48WIRE 1568 -48 1536 -48WIRE 1680 -48 1648 -48WIRE 640 -32 640 -48WIRE 160 16 160 -80WIRE 480 16 480 -16WIRE 480 16 160 16WIRE 576 16 480 16WIRE 1344 16 1344 -48WIRE 1680 16 1680 -48WIRE 1744 16 1680 16WIRE 1984 16 1984 -16WIRE 1984 16 1808 16WIRE 2064 16 1984 16WIRE 2224 16 2128 16WIRE 240 80 240 -112WIRE 640 112 640 64WIRE 736 112 640 112WIRE 640 128 640 112WIRE 160 144 160 16WIRE 1984 144 1984 16WIRE -96 192 -304 192WIRE 48 192 -32 192WIRE 96 192 48 192WIRE 1344 192 1344 96WIRE 1760 192 1344 192WIRE 1888 192 1888 -16WIRE 1888 192 1824 192WIRE 1920 192 1888 192WIRE 1344 240 1344 192WIRE 48 272 48 192WIRE 288 272 48 272WIRE 640 272 640 208WIRE 640 272 368 272WIRE 1984 272 1984 240WIRE 2096 272 1984 272WIRE -304 288 -304 192WIRE 736 304 736 112WIRE 2096 304 2096 272WIRE 2336 304 2336 -256WIRE 160 320 160 240WIRE 240 320 240 160WIRE 240 320 160 320WIRE 160 336 160 320WIRE 240 368 240 320WIRE 1008 368 1008 -48WIRE 1104 368 1008 368WIRE 1200 368 1168 368WIRE 1344 368 1344 320WIRE 1344 368 1280 368WIRE 1392 368 1344 368WIRE 1584 368 1472 368WIRE 1680 368 1680 16WIRE 1680 368 1648 368WIRE 2224 368 2224 16WIRE 2480 368 2480 -256WIRE 1888 384 1888 192WIRE 640 416 640 272WIRE 1984 432 1984 272WIRE 240 464 240 432WIRE -304 576 -304 368WIRE 160 576 160 416WIRE 160 576 -304 576WIRE 240 576 240 544WIRE 240 576 160 576WIRE 640 576 640 496WIRE 640 576 240 576WIRE 736 576 736 368WIRE 736 576 640 576WIRE 1152 576 736 576WIRE 1888 576 1888 464WIRE 1888 576 1152 576WIRE 1984 576 1984 512WIRE 1984 576 1888 576WIRE 2096 576 2096 368WIRE 2096 576 1984 576WIRE 2224 576 2224 448WIRE 2224 576 2096 576WIRE 2336 576 2336 368WIRE 2336 576 2224 576WIRE 2480 576 2480 448WIRE 2480 576 2336 576WIRE 1152 672 1152 576FLAG 1152 672 0FLAG 2224 16 opIOPIN 2224 16 OutSYMBOL npn 96 144 R0SYMATTR InstName Q1SYMATTR Value BC546BSYMBOL res 144 320 R0SYMATTR InstName R1SYMATTR Value 4.7kSYMBOL res 224 448 R0SYMATTR InstName R2SYMATTR Value 100SYMBOL cap 224 368 R0SYMATTR InstName C1SYMATTR Value 22µSYMBOL res 144 -176 R0SYMATTR InstName R3SYMATTR Value 120kSYMBOL res 384 256 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R4SYMATTR Value 150kSYMBOL res 656 -128 R180WINDOW 0 36 76 Left 2WINDOW 3 36 40 Left 2SYMATTR InstName R5SYMATTR Value 1.8kSYMBOL res 656 224 R180WINDOW 0 36 76 Left 2WINDOW 3 36 40 Left 2SYMATTR InstName R6SYMATTR Value 470SYMBOL res 656 512 R180WINDOW 0 36 76 Left 2WINDOW 3 36 40 Left 2SYMATTR InstName R7SYMATTR Value 1.2kSYMBOL cap 720 304 R0SYMATTR InstName C2SYMATTR Value 22µSYMBOL cap 464 -80 R0SYMATTR InstName C3SYMATTR Value 220pSYMBOL npn 576 -32 R0SYMATTR InstName Q2SYMATTR Value BC546BSYMBOL cap 832 -64 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C4SYMATTR Value 4.7µSYMBOL res 1136 -64 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R8SYMATTR Value 4.7kSYMBOL res 1312 -64 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R9SYMATTR Value 50kSYMBOL res 1504 -64 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R10SYMATTR Value 50kSYMBOL res 1664 -64 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R11SYMATTR Value 4.7kSYMBOL res 1296 352 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R12SYMATTR Value 50kSYMBOL res 1488 352 R90WINDOW 0 0 56 VBottom 2WINDOW 3 32 56 VTop 2SYMATTR InstName R13SYMATTR Value 50kSYMBOL res 1360 112 R180WINDOW 0 36 76 Left 2WINDOW 3 36 40 Left 2SYMATTR InstName R14SYMATTR Value 39kSYMBOL res 1360 336 R180WINDOW 0 36 76 Left 2WINDOW 3 36 40 Left 2SYMATTR InstName R15SYMATTR Value 5.6kSYMBOL cap 1824 176 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C5SYMATTR Value 100nSYMBOL cap 2128 0 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C6SYMATTR Value 4.7µSYMBOL cap 2112 368 R180WINDOW 0 24 56 Left 2WINDOW 3 24 8 Left 2SYMATTR InstName C7SYMATTR Value 4.7µSYMBOL cap 2352 368 R180WINDOW 0 24 56 Left 2WINDOW 3 24 8 Left 2SYMATTR InstName C8SYMATTR Value 22µSYMBOL res 1872 -112 R0SYMATTR InstName R16SYMATTR Value 180kSYMBOL res 1872 368 R0SYMATTR InstName R17SYMATTR Value 33kSYMBOL res 1968 416 R0SYMATTR InstName R18SYMATTR Value 1kSYMBOL res 1968 -112 R0SYMATTR InstName R19SYMATTR Value 3.9kSYMBOL cap -32 176 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C9SYMATTR Value .22µSYMBOL voltage -304 272 R0WINDOW 3 24 152 Left 2WINDOW 123 24 124 Left 2WINDOW 39 0 0 Left 2SYMATTR InstName V1SYMATTR Value SINE(0 .001 300 0 0 0 500)SYMATTR Value2 AC .01SYMBOL voltage 2480 352 R0WINDOW 123 0 0 Left 2WINDOW 39 24 124 Left 2SYMATTR InstName V2SYMATTR Value 18SYMATTR SpiceLine Rser=10SYMBOL cap 1168 352 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C10SYMATTR Value 10nSYMBOL cap 1648 352 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C11SYMATTR Value 10nSYMBOL npn 1920 144 R0SYMATTR InstName Q3SYMATTR Value BC546BSYMBOL res 2208 352 R0SYMATTR InstName R20SYMATTR Value 10kSYMBOL cap 1808 0 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C12SYMATTR Value 22µSYMBOL cap 1360 -176 R90WINDOW 0 0 32 VBottom 2WINDOW 3 32 32 VTop 2SYMATTR InstName C13SYMATTR Value 100nSYMBOL res 224 64 R0SYMATTR InstName R21SYMATTR Value 12kTEXT 48 -408 Left 2 !;ac dec 50 20 200000TEXT 616 -392 Left 2 !.tran 1s  MK
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Original article at https://www.element14.com/community/message/226265?tstart=0#226265
Re: Colorsound Power boost noise issue [message #171091 is a reply to message #171011] Sun, 30 July 2017 16:09 Go to previous messageGo to next message
messages@element14.co
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Perhaps the feedback through the 150K resistor is a bit delayed causing a unwanted phase shift.  You could try a small cap between the collector and base of Q1 or possibly a small speed-up cap across the 150K resistor to see if it makes a difference.
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Original article at https://www.element14.com/community/message/226254?tstart=0#226254
Re: Colorsound Power boost noise issue [message #171096 is a reply to message #171011] Mon, 31 July 2017 04:14 Go to previous messageGo to next message
messages@element14.co
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Hi Andy, and Others, Tonight I breadboarded the two transistor input amplifier so that I could see what was happening . Here is my bread board set up.  I am using  2N22222N2222 transistors and otherwise I have nominally duplicated what is on the schematic of the design Andy is using My input signal is 1 kHz 5 V PP I have taken pictures of the scope in the following circumstances Minimal Gain with and without a load on the output and Max Gain with and without a load on the output  Here is minimal Gain without a load followed by minimal Gain with a load. The load that I am using is a small Stereo Audio Amp with a relatively low 4 k DC input resistance.  No Load Amplifier attached  Max with No Load  Max with Amplifier attached. I found that the gain control had almost no effect on the voltage of the output but instead it acted like the duty cycle control on a PWM output. By reading the Vrms I was able to see more dramatically the effect of the gain control. The distortion of the wave form must be the Color that the pedal is designed to enter into the signal that goes to the main amp. I saw no signs of any oscillation at high gain. This of course is a totally different environment from what Andy has but it probably indicates that the design itself is sound. After I posted to this point I got to thinking that my 5 V PP was probably over driving the input of the amp so I went back and ran another test using 0.5 V PP for the input. The first thing I noticed was that my Gain control seemed to flip. What I had interpreted as a Max Gain before now looked like Min Gain. I also noticed at low Gain levels the amplifier produce an undistorted output. Sine wave in sine wave out. As I turned the Gain slowly up the output began to show clipping as it reached   4 Volts and continued to worsen until at full gain it looked again like the square wave we were seeing in my first tests. Here is a sequence of pictures as I turned the gain slowly up from Minimum gain to Maximum Gain. Note that in this sequence the channels are displaying different vertical scales. Channel one is input and channel two is output. Min GainClipping begins on the outputFull Gain with 0.5 V PP inputI believe the first part of this post was a display of garbage in and garbage out but I will leave it as it illustrates quite well the amount I still need to learn. John
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Original article at https://www.element14.com/community/message/226319?tstart=0#226319
Re: Colorsound Power boost noise issue [message #171097 is a reply to message #171011] Mon, 31 July 2017 08:03 Go to previous messageGo to next message
messages@element14.co
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Hi Michael, Many thanks for chipping in with this issue, it certainly has had me scratching my head for the last 2 weeks. Regarding the guitar volume, if you check the video above (I've linked to it here as well to save you searching) you will notice that when i turn the guitar volume all the way off the oscillation gets louder. Also when I remove the guitar from the equation and plug in the jack plug that has the tip shorted to ground the noise is still there. I don't think the guitar volume has anything to do with the "cause" of the issue, however certainly the output impedance of the guitar does have an effect. I'm very new to effects pedal building, and will be making more as I really enjoy tinkering with electronics. I think i'll have to save up for an Oscilloscope as I think if i'm serious about doing this i'll need one.... I've never used one before, but I guess there's always You tube for tutorials and E14 forum for support in learning how to use them effectively. As John pointed out, i'm not in the US, i'm in the UK. East Anglia, Suffolk to be exact. I have discovered that my new next door neighbour is into electronics (he tinkers with arduino). anyway, I've spoken to him about this issue and we both checked the PCB over. he pointed out a couple of dodgy solder joints that he re soldered, they had no effect on the oscillation. Other than that he was at a loss. He does however have an Oscilloscope. I'm sure if i knew exactly the information we need, where to take the readings etc he would help me conduct some troubleshooting on his scope and I can report back the findings. 

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Original article at https://www.element14.com/community/message/226322?tstart=0#226322
Re: Colorsound Power boost noise issue [message #171098 is a reply to message #171011] Mon, 31 July 2017 08:09 Go to previous messageGo to next message
messages@element14.co
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Your 5V pk-pk input is overloading the amplifier so it's limiting. My simulation uses a 2mV p-p sine wave input. With the pot at max the actual gain of the circuit depends on transistor characteristics and other parasitic values - my simulation gives a gain of 400 (52dB), at min gain it's about 4 (12dB). I've seen guitars put out 3V p-p with hard (but not ridiculous) strumming so your initial measurement may be typical of what people like about the sound of the circuit. MK
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Original article at https://www.element14.com/community/message/226275?tstart=0#226275
Re: Colorsound Power boost noise issue [message #171099 is a reply to message #171011] Mon, 31 July 2017 08:14 Go to previous messageGo to next message
messages@element14.co
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Connect up the pedal with the shorting plug in the input and take scope traces from the output with the gain at max and min and the tone controls flat. We should be able to see the signal you can hear and this should be  a big clue about what is wrong. I'm closer to you than the US but 330 miles or 6hrs driving away - so get you neighbor's scope on it before bringing it here ! MK
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Original article at https://www.element14.com/community/message/226276?tstart=0#226276
Re: Colorsound Power boost noise issue [message #171100 is a reply to message #171011] Mon, 31 July 2017 08:34 Go to previous messageGo to next message
messages@element14.co
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Hi All, I'm really grateful for all the help you're all giving with this issue, It is very much appreciated  I'm very new to effects pedal building, and will be making more as I really enjoy tinkering with electronics. I think i'll have to save up for an Oscilloscope as I think if i'm serious about doing this i'll need one.... I've never used one before, but I guess there's always You tube for tutorials and E14 forum for support in learning how to use them effectively. As John pointed out, i'm not in the US, i'm in the UK. East Anglia, Suffolk to be exact. I have discovered that my new next door neighbour is into electronics (he tinkers with arduino). anyway, I've spoken to him about this issue and we both checked the PCB over. he pointed out a couple of dodgy solder joints that he re soldered, they had no effect on the oscillation. Other than that he was at a loss. He does however have an Oscilloscope. I'm sure if i knew exactly the information we need, where to take the readings etc he would help me conduct some troubleshooting on his scope and I can report back the findings. Second to all that, I've decided to breadboard the whole circuit. As soon as I have it loaded on a board i'll post a video of my experiments.... Again, I've only really used a breadboard for smaller circuits, and have never built one this big on a breadboard...... I'm sure i'll get something wrong along the way, but i'll persevere. I've just read Michaels response to my post further up.... I'll speak to my neighbour tonight and see what comes out of that investigation. I'll also still try and breadboard the circuit as I think that may show up if any of the components are failing because it'll be easier to swap them out.
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Original article at https://www.element14.com/community/message/226323?tstart=0#226323
Re: Colorsound Power boost noise issue [message #171101 is a reply to message #171011] Mon, 31 July 2017 08:44 Go to previous messageGo to next message
messages@element14.co
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What I can't seem to understand, is that the PCB design is as per the original single sided PCB board, and the component values are the same..... This thing should have just gone together with no issues.... I'm thinking maybe the PCB traces might be slightly incorrect and I've not noticed. Stu Castledine throws these things together, and everyone is perfect. There must be something with the PCB, or the pots maybe. I have noticed that the treble pot is microphonic when you tap the terminals on the pot, and the bass pot also but to a lesser extent.   Here's a link to Stu Castledine's web site where the official reissue pedals are sold. There is a nice gut shot of the components which should show that mine isn't far off. I even sent Stu an email showing him my effort and he praised the board and my attention to detail. Obviously he's not going to help troubleshoot the issue, and neither should he. Castledine Electronics and Colorsound
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Original article at https://www.element14.com/community/message/226324?tstart=0#226324
Re: Colorsound Power boost noise issue [message #171103 is a reply to message #171011] Mon, 31 July 2017 09:32 Go to previous messageGo to next message
messages@element14.co
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To simplify my breadboard set up, I shall start by just bread boarding the pre-amp stage as john has done.
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Original article at https://www.element14.com/community/message/226326?tstart=0#226326
Re: Colorsound Power boost noise issue [message #171104 is a reply to message #171011] Mon, 31 July 2017 10:04 Go to previous messageGo to next message
messages@element14.co
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https://en.wikipedia.org/wiki/Motorboating_(electronics)
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Original article at https://www.element14.com/community/message/226277?tstart=0#226277
Re: Colorsound Power boost noise issue [message #171106 is a reply to message #171011] Mon, 31 July 2017 13:07 Go to previous messageGo to next message
messages@element14.co
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Jon, I've read that article and that's exactly what it is.... I just need to identify what's causing it.
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Original article at https://www.element14.com/community/message/226312?tstart=0#226312
Re: Colorsound Power boost noise issue [message #171111 is a reply to message #171011] Mon, 31 July 2017 17:01 Go to previous messageGo to next message
messages@element14.co
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Couple of things you could try without a 'scope. It would be interesting to try increasing the size of the capacitor across the supply (if you solder the same size cap in parallel with it you'll double the capacitance) and see what effect it has. Does the frequency change? Do you need more gain to get it going? You don't know whether it's just the amp at the start that's oscillating or whether it's coming back from the output stage. One approach would be to split the circuit at the coupling capacitor between the preamp and the tone control (lift the leg of the cap on the tone control side), disable the tone control (wire the disconnected input to ground) and wire the preamp output (the free leg of the cap) to the output jack. Then you could see if the preamp will motorboat for itself or whether the loop incorporates the tone control.
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Original article at https://www.element14.com/community/message/226379?tstart=0#226379
Re: Colorsound Power boost noise issue [message #171114 is a reply to message #171011] Tue, 01 August 2017 04:02 Go to previous messageGo to next message
messages@element14.co
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Hi Andy and Others, In a new experiment tonight I wanted to see how low the input to the two transistor amplifier had to be so that the output would not clip at full volume. This turned out to be at the limits of my test equipment so my results were not very precise.  Here we have an input of 1 kHz at 12.2 mV rms and the gain control is at max. This produces an output with no load of 3.56 V rms and an approximate gain of 300.   In this photo we have set the gain control to minimum. While I have not changed the input from the signal generator we see that the scope is now calculating the input voltage to be 11.1 mV rms. The output with no load is now 51.4 mV rms for a gain of approximately 5. Any setting of the gain control or increase in the input that pushes the output beyond 3.6 V rms shows clipping on the output. John
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Original article at https://www.element14.com/community/message/226410?tstart=0#226410
Re: Colorsound Power boost noise issue [message #171119 is a reply to message #171011] Tue, 01 August 2017 08:15 Go to previous messageGo to next message
messages@element14.co
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Jon, many thanks for your input. i'll try both tonight, and report back.......
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Original article at https://www.element14.com/community/message/226414?tstart=0#226414
Re: Colorsound Power boost noise issue [message #171120 is a reply to message #171011] Tue, 01 August 2017 08:22 Go to previous messageGo to next message
messages@element14.co
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I bread boarded the pre-amp stage last night... Plugged in the guitar and the volume control didn't alter anything at all.... There was a slight difference in tone but other than that nothing. Apart from that there was no oscillation, which was a good start. I'll re-check my connections tonight as i may have wired something incorrectly. I have tried wiring the whole circuit onto the bread board, but got it wrong twice with no signal at all into the amp. I think i need to "visually" split the circuit into 3 stages across the bread board, and then join them together. That way I can build the circuit in 3 stages, which is a lot easier than trying to build it as one complete circuit which is how I did it before. it got a tad confusing, and messy to say the least
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Original article at https://www.element14.com/community/message/226415?tstart=0#226415
Re: Colorsound Power boost noise issue [message #171121 is a reply to message #171011] Tue, 01 August 2017 09:04 Go to previous messageGo to next message
messages@element14.co
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This turned out to be at the limits of my test equipment so my results were not very precise.You are allowed to put an attenuator at the input if you want to. The input resistance of the preamp is around 150k, so it would hardly load a simple potential divider if you keep the values low. Measure what goes into the attenuator and divide by the attenuation. Alternatively, have a look and see what your test meters can manage measuring AC.
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Original article at https://www.element14.com/community/message/226423?tstart=0#226423
Re: Colorsound Power boost noise issue [message #171122 is a reply to message #171011] Tue, 01 August 2017 09:33 Go to previous messageGo to next message
messages@element14.co
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Before pulling the circuit about, I think there's another way to see if it's just the preamp. Set the treble and bass controls to the mid position, bring up the gain until it's just motorboating, then turn down the bass and see what happens. If the oscillation disappears again, then the loop is right through to the output and back again (because we're reducing the loop gain below the level at which it can sustain the oscillation). If the oscillation just steadily gets quieter, then it's just the preamp oscillating (the tone control is doing it's normal job of attenuating the low frequencies). [I think that works but I'm a little unsure, because adjusting the pot might change the load that the preamp sees. That's the trouble with this kind of faultfinding - the way everything interacts.] I seem to remember that you mentioned at some point you might be using 'vintage' components. Does the board with the problem have old capacitors on it or are they new ones (I mean the electrolytics, the others wouldn't give you any problems)?
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Original article at https://www.element14.com/community/message/226425?tstart=0#226425
Re: Colorsound Power boost noise issue [message #171128 is a reply to message #171011] Tue, 01 August 2017 14:36 Go to previous messageGo to next message
messages@element14.co
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Hi Jon,By this morning my mind had finally realized that I wasn't at the limit as I still could switch the oscilloscope to RX1 and then I read your excellent suggestion to use an attenuator on my signal generator. I retract my statement and tonight I will recheck my readings.John
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Original article at https://www.element14.com/community/message/226443?tstart=0#226443
Re: Colorsound Power boost noise issue [message #171130 is a reply to message #171011] Tue, 01 August 2017 18:30 Go to previous messageGo to next message
messages@element14.co
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Right, I have an update. Following Jon Clifts recommendations I tied a second input capacitor to the board and there was no real change in the noise. Now the interesting part. I tried Jon's other suggestion of disconnecting the pre-amp output transistor and connecting it directly to the output jack, and guess what?.......... I'll let you see the video  

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Original article at https://www.element14.com/community/message/226481?tstart=0#226481
Re: Colorsound Power boost noise issue [message #171131 is a reply to message #171011] Tue, 01 August 2017 19:50 Go to previous messageGo to next message
messages@element14.co
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Hi Andy,I think you got the wrong capacitor. If my reading is correct it should have been the small 4.7 uF cap on the other side of the board. John
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Original article at https://www.element14.com/community/message/226482?tstart=0#226482
Re: Colorsound Power boost noise issue [message #171132 is a reply to message #171011] Tue, 01 August 2017 22:06 Go to previous messageGo to next message
messages@element14.co
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Ooops! I'll try again Thanks John
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Original article at https://www.element14.com/community/message/226483?tstart=0#226483
Re: Colorsound Power boost noise issue [message #171133 is a reply to message #171011] Tue, 01 August 2017 22:54 Go to previous messageGo to next message
messages@element14.co
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Ok chaps, Now I've lifted the correct capacitor (thanks John ), I've tried the test again.... And the motor boating is still there, which at least tells us that it's root cause is in the pre-amp section 

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Original article at https://www.element14.com/community/message/226485?tstart=0#226485
Re: Colorsound Power boost noise issue [message #171140 is a reply to message #171011] Wed, 02 August 2017 04:21 Go to previous messageGo to next message
messages@element14.co
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Hi Andy, Does it motor boat when the guitar isn't plugged in? John
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Original article at https://www.element14.com/community/message/226534?tstart=0#226534
Re: Colorsound Power boost noise issue [message #171141 is a reply to message #171011] Wed, 02 August 2017 05:27 Go to previous messageGo to next message
messages@element14.co
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John, yes. it does..... I tried it without the guitar plugged in, and also with the shorting plug and it still motor boats. Without the guitar plugged in it is quieter, but it is still there. Check out the short video 

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Original article at https://www.element14.com/community/message/226490?tstart=0#226490
Re: Colorsound Power boost noise issue [message #171142 is a reply to message #171011] Wed, 02 August 2017 05:32 Go to previous messageGo to next message
messages@element14.co
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While i have it disconnected from the tone section and the output section, now is an opportune time to get some scope readings probably of just the pre-amp section seeing as it looks like that's where it's originating from.
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Original article at https://www.element14.com/community/message/226491?tstart=0#226491
Re: Colorsound Power boost noise issue [message #171143 is a reply to message #171011] Wed, 02 August 2017 05:40 Go to previous messageGo to next message
messages@element14.co
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These tests seem to confirm that the noise is coming from the 2 transistor amplifier. I was a little surprised that your touching the volume control had the effect that it did. The shaft of the control should be isolated from the input and grounded through the mounting screw of the control. I have to think about all of this some more. Perhaps some of this will make more sense to Jon, Michael or Shabaz than it make to me. John
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Original article at https://www.element14.com/community/message/226492?tstart=0#226492
Re: Colorsound Power boost noise issue [message #171144 is a reply to message #171011] Wed, 02 August 2017 06:16 Go to previous messageGo to next message
messages@element14.co
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If you don't like the idea of using a negative feedback capacitor to kill the oscillation, you could investigate the pot. Maybe the pot has parasitic capacitance that is adding unwanted gain. (and touching it will alter this parasitic capacitance). You could try substituting a resistor for the pot to see if this is the problem.
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Original article at https://www.element14.com/community/message/226493?tstart=0#226493
Re: Colorsound Power boost noise issue [message #171145 is a reply to message #171011] Wed, 02 August 2017 07:02 Go to previous messageGo to next message
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As an experiment, can you now try increasing the size of the capacitor that goes from the emitter of Q2 to ground (currently 22uF). Let's overdo it a bit and go to 100uF if you've got one to hand - if not, parallel some smaller values. Does that stop the oscillation?
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Original article at https://www.element14.com/community/message/226515?tstart=0#226515
Re: Colorsound Power boost noise issue [message #171146 is a reply to message #171011] Wed, 02 August 2017 07:22 Go to previous messageGo to next message
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I'll do that tonight Jon.... At work now. I know for sure I don't have 100uf to hand, so i'll likely have to daisy chain a few together to make the value up.
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Original article at https://www.element14.com/community/message/226503?tstart=0#226503
Re: Colorsound Power boost noise issue [message #171147 is a reply to message #171011] Wed, 02 August 2017 07:54 Go to previous messageGo to next message
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Could the volume pot be at fault, and thus contributing to the motor boating? Douglas Wong above has suggested as such. To test this theory i'll remove the pot and solder a 10k resistor in its place as another experiment.
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Original article at https://www.element14.com/community/message/226504?tstart=0#226504
Re: Colorsound Power boost noise issue [message #171151 is a reply to message #171011] Wed, 02 August 2017 18:16 Go to previous messageGo to next message
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Ok, Latest video, I connected 4 22uf caps and wired them all as Jon suggested above..... No cigar, Here's the video 

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Original article at https://www.element14.com/community/message/226519?tstart=0#226519
Re: Colorsound Power boost noise issue [message #171152 is a reply to message #171011] Wed, 02 August 2017 18:58 Go to previous messageGo to next message
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Hello guys.... This is probably the last update .... it would appear i've discovered what the root course of the issue is. I have done one last experiment, I tried Douglas Wong's suggestion of trying a 10k resistor in place of the volume pot..... Well, just watch the video 

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Original article at https://www.element14.com/community/message/226546?tstart=0#226546
Re: Colorsound Power boost noise issue [message #171153 is a reply to message #171011] Wed, 02 August 2017 18:58 Go to previous messageGo to next message
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Hi Andy,I don't think it will be the volume pot as it is zeroed out at full gain and becomes a non functioning part. You mentioned replacing it with a 10 K resistor but for full gain I think you will need a piece of wire.John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226547?tstart=0#226547
Re: Colorsound Power boost noise issue [message #171155 is a reply to message #171011] Wed, 02 August 2017 19:06 Go to previous messageGo to next message
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John.. i'll try that before I get too carried away
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Original article at https://www.element14.com/community/message/226548?tstart=0#226548
Re: Colorsound Power boost noise issue [message #171156 is a reply to message #171011] Wed, 02 August 2017 19:10 Go to previous messageGo to next message
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Dammit... It's still there  Back to the drawing board
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Original article at https://www.element14.com/community/message/226549?tstart=0#226549
Re: Colorsound Power boost noise issue [message #171158 is a reply to message #171011] Wed, 02 August 2017 21:45 Go to previous messageGo to next message
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Hi Andy,Please give me more information on the transistors that you are using. Are they the same part number as the originals? If not what are their numbers and what were the originals numbers? I do not believe in magic so there has to be a reason and a solution.John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226558?tstart=0#226558
Re: Colorsound Power boost noise issue [message #171159 is a reply to message #171011] Wed, 02 August 2017 22:56 Go to previous messageGo to next message
messages@element14.co
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I'm a rank amateur at this audio lark, but this is what we've done so far and where I think I'm going with it. (Doug and John evidently have some other ideas, so listen to what they suggest too.) You have oscillation. It's low frequency, right at the bottom end of the frequencies that you'd expect a piece of audio equipment to deal with. Usually the problem is at the other end of the scale (the high frequencies where signals can be easily coupled to places they shouldn't be by small amounts of capacitance between wires). At the low end it takes much more to couple signals, even with the comparatively high input resistance that you have here. At this kind of frequency, the power rail (even with its [somewhat light] decoupling cap) have to be a suspect too (which also means the pcb layout as well - the ground trace that runs to the gain pot and then to the output stage isn't very good). You divided the circuit, because there was the possibility that the feedback loop that's leading to the oscillation was through the whole instrument. Now it looks like it's just the preamp.The preamp has two feedback loops, as Michael mentioned above. (If he says anything be sure to take note because he's a pro at this stuff and I'm not.) The DC feedback that sets the voltage at the base of the input transistor derives from the emitter of Q2. That's held from moving by the capacitor that you've just tried changing. That capacitor can't operate all the way down to dc and slow changes at the emitter will pull the voltage around. By getting you to beef that up, you were reducing the possibilty of unwanted AC feedback via that path. The low frequency of the oscillation requires a long time constant - if you were trying to build an oscillator to operate at this frequency it would involve large capacitors (at least it would if it were a simple transistor circuit), so the electrolytics are still suspect in this. The next one to look at is the coupling capacitor that connects the gain pot to the circuit. This time we want to try decreasing the value. Try a 15uF or a 10uF there rather than the 22uF. By lowering the value we're moving up the frequency at which the low-frequency roll-off occurs. That means there will be less gain left once we're down at the oscillation frequency. If that kills the oscillation, the next thing would be to go back to a different 22uF cap and see what happens (the supposition would be that you are unlucky and have a cap in there that's very high in the tolerance range). Are you using old capacitors? I've tried measuring some old electrolytics (from decades ago) and they not only measure high of the value on them, but they are outside the tolerance (that may or may not be typical, I don't know). I'd be very wary of old capacitors because they might not manage the voltage spec either (which might be a further possibilty for your problem). Apparently, old capacitors tend to reform themselves if run for a few hours (so I've read), so you might find things would come right if you left the thing powered for an extended period of time.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226601?tstart=0#226601
Re: Colorsound Power boost noise issue [message #171161 is a reply to message #171011] Wed, 02 August 2017 23:54 Go to previous messageGo to next message
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Hi Andy,The BC184L is a general purpose NPN audio transistor and crosses to the transistors that I used in my breadboard circuit. It is unlikely that they are the cause, especially since you have two units making this noise but I would swap in a couple different ones just to be certain. I would even be tempted to try a slightly different NPN transistor. I am not very familiar with the European numbers so I will leave that to you or perhaps Michael will know a good common one to try.John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226562?tstart=0#226562
Re: Colorsound Power boost noise issue [message #171162 is a reply to message #171011] Thu, 03 August 2017 05:37 Go to previous messageGo to next message
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Hi Jon, I have 2 boards exhibiting the same issue. The only similarity between the two are the transistors and the polarised electrolytics. The electrolytics are brand new not old, however in my search for a solution I'll buy some more from Farnell. On the second board all the polyester caps were brand new, and the eletcrolytics were vishay brand, and also brand new. When you say the "the ground trace that runs to the gain pot and then to the output stage isn't very good" do you actually mean the quality of the trace or the circuit design? Is there any mileage in revisiting the circuit and re-etching another board?
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226566?tstart=0#226566
Re: Colorsound Power boost noise issue [message #171163 is a reply to message #171011] Thu, 03 August 2017 09:42 Go to previous messageGo to next message
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I was just being very picky about the layout - it won't be the cause of your problem or everyone using this layout would see it (and you've already shown that the output stage isn't involved). Ideally the ground tracks would go back separately to closer to the star point rather than have the shared segment. The designer has partially mitigated any possible problem by widening the first segment of track to get the resistance down and that was evidently ok. The comment from the guy at DIYStompboxes is sensible advice and very easy to try.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226567?tstart=0#226567
Re: Colorsound Power boost noise issue [message #171164 is a reply to message #171011] Thu, 03 August 2017 10:55 Go to previous messageGo to next message
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Hi Jon, I'll try the suggestion regarding the 10k resistor on the input. As a matter of interest I've just found a gut shot of an early power boost... and on the trace side it's had an extra resistor soldered to it........ When you look hard you can make out brown, black & orange, 10k..... Coincidence? I've checked this photograph and it looks like it's been soldered between the output and ground, not the input so I don't know what its purpose is. Just thought i'd put this on the table , just in case. 
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226590?tstart=0#226590
Re: Colorsound Power boost noise issue [message #171165 is a reply to message #171011] Thu, 03 August 2017 11:44 Go to previous messageGo to next message
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Just had a response from Stu Castledine, he builds these for Macaris in London..... He knows this circuit better than  anybody: The email I sent him is this one: "Stu, I have been trying to cure the noise issue I have with this power boost clone pedal, and have been in long troubleshooting discussions with the tech heads over at the element 14 forum. you can see the posts here: <Link to this forum> The ticking noise I'm getting has been identified as "motor boating", and it's coming from the 2 transistor pre-amp section of the power boost circuit, I proved this by disconnecting the 4.7uf capacitor that connects the pre amp to the tone section and wiring the negative side of the cap directly to the output jack. This is driving me up the wall. Have you ever experienced this, and if so what was the work around? I appreciate you're busy, but have you got any suggestions? bear in mind the PCB layout is a direct trace of a genuine board, and the component values are to the original schematic. Regards, Andy" And his response: "Hi Andy, Thanks for the link.  Yes, that's definitely motor boating, but I've never had this problem and I've "thrown together" well over a hundred Power Boosts.   I would have suggested the same mods posted in that thread: more capacitance across the supply rails, less capacitance on the volume control and ensuring a good mechanical connection between the enclosure and 0V.  That said, it is a proven design, so it should be possible to make it work with the standard parts values.   It's odd that both of your circuits exhibit the same instability. Sorry I can't be more help, I think you just have to go back and double check everything - it must be something common to both of your builds. Best regards, Stu"
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226580?tstart=0#226580
Re: Colorsound Power boost noise issue [message #171166 is a reply to message #171011] Thu, 03 August 2017 14:33 Go to previous messageGo to next message
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Hi Andy, I have been going back over things and I noticed this anomaly. The transistors that I am using are a direct cross for the BC184L and their pin configurations are: Pin 1 Emitter, Pin 2 Base, and Pin 3 Collector. I also noticed that your board layout has been labeled Pin 1 Emitter, Pin 2 Collector, and Pin 3 Base. Now I can't see from your picture if you have rotated pins 2 and 3 so that they are in the correct spot but if not you may have the base and collector switched on your build. John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226581?tstart=0#226581
Re: Colorsound Power boost noise issue [message #171167 is a reply to message #171011] Thu, 03 August 2017 14:39 Go to previous messageGo to next message
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Hi Andy, Scratch my last post. I checked the data sheet of the BC184L, which I should have done before posting, and its pin outs are correct for your board layout. Apparrently while my 2N2222 is electrically equivalent the pin outs are different. Back to the drawing board. John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226570?tstart=0#226570
Re: Colorsound Power boost noise issue [message #171168 is a reply to message #171011] Thu, 03 August 2017 15:50 Go to previous messageGo to next message
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No problem John, I was just going to send you the 184L datasheet when you posted the second message. Yes, Jon Clift may remember the posts from last year regarding this circuit and the transistors. I'm aware the pin outs are different on the 184L's, and that's why I wanted to use these specific transistors as they fit the board without twisting the legs etc. Also they are exactly what are in the reproduction pedals by Stu Castledine. I have ordered some new transistors, BC184L's only this time they are properly branded Fairchild transistors. I'm suspect that the transistors in the board might be below par. Where I work we have a good electronics department, they design and build mechatronics for cars. Anyhow, I spoke on the phone to one of the techies in mechatronics and he asked me if i tried changing the transistors. I said at this time no, i hadn't... So he suggested changing them for a different type, not from my batch of transistors, working on the assumption that they might be crappy transistors from an unknown source. I have some standard BC184's which i'll try tonight. I must say at this point, I would have asked the guys in our electronics department to help me previous to this, but they are so busy working on a new project they don't have time to even stick my board on an oscilloscope  I've been posting on a pedal forum, and a poster there has noticed that just isolating the pre-amp stage by lifting the 4.7uf cap doesn't totally isolate the pre-amp from the rest of the circuit. He's also suggested i lift the 180k and the 3.9k resistors at the output end from the 18v power supply into the output. His thinking is that there may be some bad interaction between the high-gain front end and the back end, fed thru the supply. the R//C would isolate, possibly disprove his theory. I'll do that also at least then we know the pre-amp is fully isolated form the rest of the circuit.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226633?tstart=0#226633
Re: Colorsound Power boost noise issue [message #171169 is a reply to message #171011] Thu, 03 August 2017 15:55 Go to previous messageGo to next message
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Just noticed that the pin outs on BC184L and BC184 are different  BC184L are ECB BC184 are CBE I'll have to put them in back to front and twist legs 2 and 3 round
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Original article at https://www.element14.com/community/message/226634?tstart=0#226634
Re: Colorsound Power boost noise issue [message #171170 is a reply to message #171011] Thu, 03 August 2017 16:09 Go to previous messageGo to next message
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I have only one request at this point. Please don't give up before we figure this out as my curiosity would self destruct.John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226635?tstart=0#226635
Re: Colorsound Power boost noise issue [message #171171 is a reply to message #171011] Thu, 03 August 2017 16:11 Go to previous messageGo to next message
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I can't give up!!!.... I have to get my pedal fixed, no ifs or buts. Once i know the fix for my pedal I have to recall the one i sold to a friend and apply the same fix to his. Luckily he's not used it yet, so is oblivious to the issue
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226636?tstart=0#226636
Re: Colorsound Power boost noise issue [message #171172 is a reply to message #171011] Thu, 03 August 2017 16:18 Go to previous messageGo to next message
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Question, and this is just off the cuff. My PCB was home etched, it was a heat transfer jobbie, ironed on and then etched with Ferric Choride. I am left with just the basic copper tracks. The original board, if you look at the photo a few posts above has had the tracks covered in solder...... Does that make any difference to the performance of the circuit, or is it just to help stop the copper from corroding? I was thinking about liquid tinning my circuits, but that's really expensive to buy.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226637?tstart=0#226637
Re: Colorsound Power boost noise issue [message #171173 is a reply to message #171011] Thu, 03 August 2017 16:24 Go to previous messageGo to next message
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Don't worry about the tinning - it isn't normally electrically beneficial.If you are worried about corrosion (due to spilling beer into your pedal (sweat if you're into thrash (blood if Goth))) then apply some cheap conformal coating to the board (don't bother with expensive stuff and don't do it until it's definitely working ! MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226619?tstart=0#226619
Re: Colorsound Power boost noise issue [message #171174 is a reply to message #171011] Thu, 03 August 2017 16:29 Go to previous messageGo to next message
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Thanks Michael, I'll remember that..... And I never spill beer.... Not if I can help it  Back to the issue in hand....  Do you have any thoughts on what Stuart has replied with above..... He's built well over 100 of these pedals using the same design board, and the exact same components values.... No issues.My thinking is it's got to be either wafty components, bad grounding or an error on the board. He said 2 things that piqued my interest.. "It's odd that both of your circuits exhibit the same instability" & "it must be something common to both of your builds" The only thing common to both builds are the transistors (if you discount the board) Both boards have transistors from the same batch delivered to me last year. There is also the electrolytics which are the same. I've since sent him a PDF of my board layout, asking him if he'll at least say "yes it's ok", or "no... You've made a mistake" he'll hopefully reply soon.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226594?tstart=0#226594
Re: Colorsound Power boost noise issue [message #171175 is a reply to message #171011] Thu, 03 August 2017 16:48 Go to previous messageGo to next message
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Well, to quote Sherlock: Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.Which must be where we are: Look for breaks in tracks - can happen with even bought in boards. Try a ceramic capacitor (100nF or so) across the power supply near the input transistor. Any chance of getting at that scope ? MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226638?tstart=0#226638
Re: Colorsound Power boost noise issue [message #171178 is a reply to message #171011] Thu, 03 August 2017 20:26 Go to previous messageGo to next message
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The BC184L was available in different gain grades. I think there was also a BC184LB and a BC184LC (I can certainly remember BC184LBs at one place I worked). C is the highest gain group.
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Original article at https://www.element14.com/community/message/226647?tstart=0#226647
Re: Colorsound Power boost noise issue [message #171179 is a reply to message #171011] Thu, 03 August 2017 22:31 Go to previous messageGo to next message
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I've had a slight set back.... I'm now getting nothing from the board at all. i took the board to work with me today hoping that i may be able to get the guys in Mechatronics to put it on an Oscilloscope. I didn't manage to do that, and when I got it back home a couple of wires had come away from the board.. Nothing major, i just resoldered them to the board, However, now i'm getting absolutely nothing from the board. However, I've made an executive decision... i'm starting again, with a new board, new transistors, and new everything. i'm cutting the board tomorrow, and i'm etching the board probably tomorrow evening. I'll start populating the board over the weekend. I've got some new BC184L transistors arriving either Monday or Tuesday. I'll make this third board with all brand new parts. I will try and get this board working again... i just can't see where the issue is. I've checked all wires for continuity, and there's no issue there. I've checked all ground connections from the ground on the jack sockets, and then checking for continuity on the board... no problems. I'm thinking a component has failed, and i'm not able to find what one. I have unsoldered and resoldered a lot of times on this board now....  Please bear with me, and as soon as I have some news i'll post again.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226625?tstart=0#226625
Re: Colorsound Power boost noise issue [message #171180 is a reply to message #171011] Fri, 04 August 2017 08:59 Go to previous messageGo to next message
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Ok guys. This is where I am, and what I'm planning. I'm building another board, and it will be made with all brand new components. It will be using the same exact components as the 1st build, standard 1/4w carbon film resistors, brand new Vishay capacitors, brand new polyester caps, brand new etched board, brand new pots, and also brand new Fairchild BC184L transistors. The board I have been working on is dead, I'm getting nothing from it, not a peep. When I took it to work unfortunately I didn't think to protect it from being knocked in my bag, and i also packed the two 9v batteries in with the board but they were  not secured and I think maybe have shorted something on the board in transit. i will keep trying to get life into it, but at the moment I'm at a bit of a loss as to what's wrong with it.... I may change the electrolytics although I am running low on them now, and could probably do with buying more. Anyhow, onwards and upwards. This third build will be finished hopefully by Sunday. I had the board cut this morning, and I've just finished printing the trace onto photographic paper for heat transferring tonight. With this board, I'm going to pay extra attention to detail..... Just to mitigate any possible build cock-ups. I feel fairly confident where all the components go, I've been living and breathing this pedal for around a year now and the level of research I've conducted into it is stupid for such a simple pedal. However, I won't take anything for granted, and I'll check and double check the location and orientation of every component as I put it in the board. regarding the board, when I heat transfer the trace onto the board I'll ensure i leave it longer to ensure I don't get any broken tracks... I'll also ensure I touch up any tracks before I etch the board..... Although I check all the boards I make, it is possible I missed something. All my 1/4w resistors are brand new...... I've got 100's. However, I'll ensure that i check all the resistors before i solder them to ensure they are within tolerance. I want to make sure that I have everything as perfect as I can possibly make it... If this works, and I don't get any motorboating it'll be good. It may also indicate to me that the fix may well be the transistors as they will be the only things that are different between the 1st board I built, and this new 3rd board.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226629?tstart=0#226629
Re: Colorsound Power boost noise issue [message #171189 is a reply to message #171011] Sat, 05 August 2017 10:30 Go to previous messageGo to next message
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Just had a delivery of the new BC184L transistors.. I've noticed something different between the 2... Whether it's relevant or not.. They're both supposed to be Fairchild transistors, but my originals look decidedly dodgy... What are your opinions?? Original transistors  New transistors 
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Original article at https://www.element14.com/community/message/226749?tstart=0#226749
Re: Colorsound Power boost noise issue [message #171190 is a reply to message #171011] Sat, 05 August 2017 11:20 Go to previous messageGo to next message
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Hi Andy, If the print on the ones in the upper photo appears to be scratched in, then they could be fake. But they could just be old parts, since these have been produced for decades.If they were purchased from eBay then they could well be fake or used parts, the risk is quite high for fake components unless they are from a trusted source. There is money to be made it seems from desoldering parts, cleaning and straightening wires, polishing off the print and replacing with a popular component value.See here for fake (well, used) LEDs resold as new on eBay:Fake and Re-used Electronic Parts and Components
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226731?tstart=0#226731
Re: Colorsound Power boost noise issue [message #171194 is a reply to message #171011] Sun, 06 August 2017 07:29 Go to previous messageGo to next message
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Registered: March 2013
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HI guys, I have an update.... of sorts. 3 Things. 1. I've got the old board working..... Must have been a dodgy earth2. I haven't been able to build board 3 yet as I had an issue with the heat transfer.3. I've replaced the old transistors in the old board with 3 of the new one. I was playing about with the board, trying to see if i could get it working, and i came across 2 things. One i believe it stopped working because of an earth issue... not the end of the world, and easily fixable. Second, i noticed that there wasn't continuity between the track either side of Q1 collector.... I think either my soldering was crap, or the track wasn't that good (the tracks for the transistors are very small)I checked the whole board with an eye lupe, and to be honest my soldering is not the best but equally it's not the worst, but I honestly think the integrity of the board isn't that good, and also some of the soldering could be better. I had an issue with the heat transfer of the new board, so won't be able to do anything until tomorrow. as it's quite a large board I'm having trouble evenly distributing the heat over the board to ensure that the transfer has good adhesion. i'll have to have another go tomorrow night. I've replaced the old transistors with 3 of the new ones that were delivered, and I have the same issue... motor boating. BUT, and say this quite firmly, I believe my issue is 2 things, board integrity, ie, the transistors, and the signal path to and from them. and the quality of the circuit. I have soldered, un-soldered and re-soldered more times than i can remember now and the condition of the copper tracks in some places, especially around the transistors is a lot to be desired. I need to start a fresh, with all new components. If I can, I'll etch 2 boards so i have a spare.... I'll also try and bread board the pre-amp circuit again as I believe when I did it first time around i had the pin outs of the transistors wrong (I was using my neighbours BC184's.... which at the time I thought had the same pin out as my 184L's... They don't) So I need to revisit the bread board again, that i believe will prove whether it's board integrity or not.  Someone in Australia called Ian Dempsey  has contacted me via the DIYStompboxes forum and has asked me for a copy of the circuit layout. he wants to build one to, but will be using the photo resist method of circuit printing. He'll be building his pedal this week, and I've asked him to report back to me with his findings. He's an electronics engineer of 40 years, and will be trying to hopefully reproduce the motor boating i'm experiencing. He may also post in here to share the information with you guys. John wiltrout, i will get there, and I haven't given up.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226717?tstart=0#226717
Re: Colorsound Power boost noise issue [message #171198 is a reply to message #171011] Mon, 07 August 2017 19:39 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Update guys.... i've just etched PCB board number 3  This is different in so far as i used the new layout artwork I've done. Nowe to start drilling
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226866?tstart=0#226866
Re: Colorsound Power boost noise issue [message #171209 is a reply to message #171011] Wed, 09 August 2017 05:21 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Ok guys, I've populated this new board, just the pre-amp section............ And there's no issues. (There isn't a pot in there yet as I need to get one, so I've just placed a wire in there so the pedal is at full gain) 
  I believe my issues was board integrity. I believe the heat transfer maybe wasn't as good as it could have been, and maybe some of the soldering wasn't up to a good enough standard. This new board I've checked every single components as I soldered it to ensure no dry joints etc. Also the new board was made with revised artwork.... A blacker image before i transferred it to the PCB. Anyhow, I seem to have "sort of" solved it. I still don't know what caused the motor boating really, but i do know the circuit works as it is. Ian Dempsey has made one also (The guy that contacted me from Australia) and his works perfectly too with no issues.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226914?tstart=0#226914
Re: Colorsound Power boost noise issue [message #171210 is a reply to message #171011] Wed, 09 August 2017 05:26 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Congratulations - great perseverance.....
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226896?tstart=0#226896
Re: Colorsound Power boost noise issue [message #171212 is a reply to message #171011] Wed, 09 August 2017 07:39 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
This has got me so intrigued that I'm unwilling to let it go as an unsolved mystery. If you want to send me the non working board I'll look at with a scope etc and report back on E14. MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226915?tstart=0#226915
Re: Colorsound Power boost noise issue [message #171214 is a reply to message #171011] Wed, 09 August 2017 08:23 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Thanks Doug, for all your help
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226924?tstart=0#226924
Re: Colorsound Power boost noise issue [message #171215 is a reply to message #171011] Wed, 09 August 2017 08:27 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Hi Michael, If you email me your address I'm more than happy to post it to you as it is at the moment. Although i would like it back as i want to salvage all the components off it. My email is andy.betts1966@gmail.com I'll get it packed up and posted off in the next day or two.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226925?tstart=0#226925
Re: Colorsound Power boost noise issue [message #171216 is a reply to message #171011] Wed, 09 August 2017 08:36 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
I've sent you an email - I'll post my results here. MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226897?tstart=0#226897
Re: Colorsound Power boost noise issue [message #171219 is a reply to message #171011] Wed, 09 August 2017 10:27 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Thanks Michael..... Look forward to it. I'll get it in the post in the next day or 2
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226898?tstart=0#226898
Re: Colorsound Power boost noise issue [message #171222 is a reply to message #171011] Wed, 09 August 2017 13:32 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Thank You Michael,I too have an over load of curiosity on this one. I can't wait for your analysis.John
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226935?tstart=0#226935
Re: Colorsound Power boost noise issue [message #171242 is a reply to message #171011] Thu, 10 August 2017 12:32 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
I have a question regarding the circuit.... What is the purpose of the 220pf ceramic cap?? I'll tell you why i ask. The first two boards I made were slightly different layouts, one board had NOS components on it, and the other board had all new components on it..... Except 1. Apart from the electrolytics, the only component that is the same between the boards that are motor boating is the 220pf cap. Both boards have an old cap in it. This new rev 3 board that now works, is different, it has a shiny brand new 220pf cap between the base and collector of Q2.... Coincidence? That is the only part that is not common between the 2 boards that don't work, and this new one that does. It is the only component that hasn't been changed, until now. So i'm interested in knowing what's purpose is. I seem to remember reading somewhere (i can't remember where) that it's to control the amount of "feedback" in the circuit. If so i could have just stumbled on the root cause....
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226994?tstart=0#226994
Re: Colorsound Power boost noise issue [message #171243 is a reply to message #171011] Thu, 10 August 2017 12:47 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
The 220pF provides local feedback around Q2 at high frequencies. The idea is to reduce the open loop gain of the amplifier to prevent high frequency instability. If it's the wrong value it might possibly cause the problem you've been seeing. MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226980?tstart=0#226980
Re: Colorsound Power boost noise issue [message #171244 is a reply to message #171011] Thu, 10 August 2017 12:58 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
before I send you the board that's motor boating i'll change the cap to a brand new one just to see. If there's no change i'll send you the board as planned. If it cures it, well we've got the solution. I'll change it tonight, and post my result.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/227010?tstart=0#227010
Re: Colorsound Power boost noise issue [message #171249 is a reply to message #171011] Thu, 10 August 2017 14:03 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
It isn't the wrong value as I checked it... But certainly being old it could well be knackered
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/227012?tstart=0#227012
Re: Colorsound Power boost noise issue [message #171256 is a reply to message #171011] Thu, 10 August 2017 22:16 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
OK.... So changing the 220pf cap didn't work... It was worth a go...
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/226990?tstart=0#226990
Re: Colorsound Power boost noise issue [message #171304 is a reply to message #171011] Mon, 14 August 2017 09:06 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Michael, The PCB has been sent today, it's been sent special Delivery so you should get it tomorrow before 13:00. The soldering is not good after having another look at it, especially around the transistors.... This is down to the swapping out of components etc. probably needs trashing now and starting again.... See what you think Andy
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/227123?tstart=0#227123
Re: Colorsound Power boost noise issue [message #171310 is a reply to message #171011] Mon, 14 August 2017 19:24 Go to previous messageGo to next message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Michael, as a heads up.... When you get the board check the 22uf cap between the emmiter of Q1 and pin 1 of the volume pot.... This might be the root cause, or something to do with it. I just soldered this into another board and when i touch the volume pot i hear slight motor boating, but not when i DON'T touch it... It didn't happen before i soldered this cap in.
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/227162?tstart=0#227162
Re: Colorsound Power boost noise issue [message #171318 is a reply to message #171011] Tue, 15 August 2017 09:47 Go to previous messageGo to previous message
messages@element14.co
Messages: 565
Registered: March 2013
Senior Member
Hello Andy, I just received your board and connected it up with a lab power supply, signal generator and scope - it seemed to work fine. So I connected it up with batteries, signal generator and Chord practice amp - still fine. I don't have a guitar at work so I'll bring one in tomorrow. I'm not sure if this is good news or bad ! What power supply were you using. MK
EAGLE support forums at www.eaglecentral.ca :: Where the EAGLE community meets.

Original article at https://www.element14.com/community/message/227185?tstart=0#227185
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