Muffler build has no sound

M

Mr.H

New member
Troubleshooting these situations are still new to me, so bear with me; I understand there is stuff for me to learn still, and I am working thru the schematic for the first time.

Bypass signal is present, but no signal when effect engaged.
LED does not light up, either.
Rechecked all resistor values, and all seems appropriate visually. Did check with DMM, and I have some odd values, which are:
R11=1.925k
R10=537.6k
R18=90.5k
R1=OL
Got the idea to use DMM to read resistor values from an article that is supposed be written by R.G. Keen, who said "test everything."

Getting voltage into the circuit @ 8.82 and voltage at R100 is 8.60, but at LED it is 0.1.
Still unsure of how to approach the rest of this. Posting pics of my work, so far. Please advise, and thanks in advance. IMG1.jpg IMG2.jpg
IMG4.jpg
IMG5.jpg
 
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Well it is a gate (sorry had to)
Resistors can read weird when in the circuit so as long as the color code is right then the weird ones should be right. I havent used those purple caps so i cant verify if you did correct polarity for those. The fets or ic are a safe bet to be the problem but hopefully someone will tell you what the voltages are supposed to read out at so you can check.
 
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Nice job getting detailed pictures of your board and wiring.

Use some isopropyl alcohol and a toothbrush to clean up your board on the solder side. that is generally a good practice and might even help with your troubleshooting.
 
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Thanks for the responses. The color codes in the resistors are correct. The purple caps are supposed to be nichicons, but they don't look like it to me. Now I'm doubting their positioning.

Thanks for the compliment on the pictures, I understand that it's important to be able to see what to troubleshoot. I got the bottom of the board cleaned off, too.

The 2n3904's I got from mouser, but the 2n5485 I got from eBay. Last night I ordered some more , but from smallbear this time. Will post back after further troubleshooting.
 
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I've gotten the transistors socketed, the board cleaned, and I still have no sound when the pedal is activated. I also get no power to the LED. I was thinking it might have been the switch because when I tested the voltage at the LED when it's engaged, it was zero. Changed the switch, same results. Please advise.
 
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1. 4.160
2. 4.147
3. 4.146
4. 0
5. 4.121
6. 4.304
7. 4.304
8. 8.60

Pin 1 at the pot = 4.145
also took the advice to lay some more solder on it

I also replaced the purple caps with nichicons.


IMG_1.jpg IMG_4.jpg
 
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you should put together an audio probe and use it to try to follow the audio signal through your circuit. do a google search for info on how to build it and use it. it should be a big help here for your troubleshooting.
 
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I have one, and I tried tracing the circuit but got nothing in terms of output. I decided to hook the pedal up on my board and discovered that I now have sound in bypass and engaged, but the effect is not present. Not sure what to do next.

With the audio probe, I was trying to use my phone for the sound source, but not sure if I was doing something wrong, or not.
 
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I made a new audio probe, and was able to probe the circuit this time. The components before the pot are good, but when I got to the pot I wasn't hearing much, so I tested the rest of the circuit. I had audio on almost all the components, but about 1/3 of them I got static to bad noise. The transistors produced audio, and so did the IC, but on Pin 1, audio was static mostly; same with Pin 2. Pin 3 wasn't given me much of anything. C3 and R7 produced no audio when probed. The rest of the IC was good. I then went back to the pot. I got no audio at first (the knob was turned CCW all the way). I tried turning the knob clockwise, and got some audio from pins 1 & 2. Not really encouraged by this, I took the pedal and hooked up a distortion pedal, and my guitar to it, and tested it out. Same results as before, signal is present in bypass and when engaged, but the effect is not working. LED still doesn't light up, either. Not sure if I should start over, and depopulate the board, and try again, or just shelve it for good. Any help is appreciated.
 
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Have you cleaned the IN, GND, SW, OUT Pads on the PCB, lots of Crud in picture.
Have you tried a 4558 Op Amp, looks likea TL072 in there?
Make sure those Transistors are making proper connection, I refuse to use sockets on Trannies!
Those that do tin the legs with Solder to make better contact & firmer in the holes!
 
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make sure your LED is good. maybe it is in the board backwards. if the LED is good and installled the right way, then figure out why power and ground are not reaching it when the effect is turned out. troubleshooting that may help you find the reason your board is not working.

you can also take out the transistors and bend the legs to spread them apart a bit at the top before putting them back in their sockets. that puts more tension on the legs when in the sockets and may give you a better connection. as noted above, coating the legs with solder makes them fit better as well. if the leg won't fit in the socket after you do that you can remove a bit of solder from it until it fits. AFTER everything is working you can then solder the middle leg of the transistor into the socket to keep it in place, and it is not difficult to remove later if you need to swap it out.
 
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From your description it seems like your problems start at the pot or around IC1.1 input pins 2 and 3 and the output pin 1

You've already identified that from your probing so I'd check the pot first

You can check resistance across it, with no power to the circuit check what you get across lugs 1 and 3 then turn fully CCW and check resistance between 1 and 2 and 2 and 3 turn CW and check 1 and 2 and 2 and 3 again, you may not get accurate readings with the other resistances in circuit all you're doing is checking it functions correctly and that resistance changes as you rotate it

Then take your IC out of socket and reflow the solder joints

With your IC voltages looking ok I'd suspect a cold solder joint on the socket or the IC isn't fully located into the socket

If it doesn't fire up you can check you have the expected resistances on those pins

With no power to the circuit remove the IC and check resistance between pins 1 and 2 and from VREFB to pin 3 with the pot fully CW then CCW

You can see from the schematic what resistance you should get between those points e.g. pins 1 and 2 = R6 value 1M, if you got for example infinite ohms you'd know it's open circuit ie no connection any other value like 0 indicates a short or incorrect / fried resistor

So good for finding shorts etc but obviously gets more complex with parallel resistances to consider, that's when I give up, maths hurts my head!

Audio probing identifies your problem area and it's just a case of checking components solder joints etc around it
 
Last edited:
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I checked the pot, and these are the values that I got:

CW
---
Lugs 1 to 2 = 520k
Lugs 2 to 3 = 1.3r
Lugs 1 to 3 = 520k

CCW
---
Lugs 1 to 2 = 1.4r
Lugs 2 to 3 = 529.9k
Lugs 1 to 3 = 529.8k


The resistance on the IC is this:
Pins 1 to 2 = 0.999M

I don't know what VREFB is, so I didn't measure it from there to Pin 3

Anyone got any ideas? The only thing I can think of next is to remove ALL the components and start over.
 
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