Pig butt low volume, low unity gain? <<SOLVED>>

[High Lord]

Coming back to my pig butt after a year on the shelf I've hooked it up and, yeah, it's fuzzing {with one guitar and not so much with another,} it's just quiet, as in unity at full volume. Is this normal and can it be fixed?
Of note, I read the voltages and photo attached. Because I'm filtering my el cheapo power supply its starting off at 8.87v. Pertinent?
The tone off switch provides a slight boost at the cost of, well, tone.
I've attached a gut shot, not the cleanest build, especially after pulling the volume to recheck its ohms.

Maybe pulling the final drop down resistor?

Any feedback welcomed.

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[WormBoy]

Haven't built one myself, but no more than unity volume and fuzz with one guitar but no so much another (for a pedal described as a "wall of fuzz") ... sounds like you have a problem. The 8.87V on the supply is not the problem, and neither is the output resistor (which seems superfluous anyway).

I would start by checking the values of the resistors by trying with the DMM (which might not work well in the assembled circuit) or reading the color bands (which works if you have good colour vision, which I haven't). I would start with the ones that modify the gain most in the circuit: R2, R3, R6, R7, R9, R10. If they are correct, I would check their soldering, as well as the soldering of C4 and the SUS pot (as well as its value).

[High Lord]

Haven't built one myself, but no more than unity volume and fuzz with one guitar but no so much another (for a pedal described as a "wall of fuzz") ... sounds like you have a problem. The 8.87V on the supply is not the problem, and neither is the output resistor (which seems superfluous anyway).

I would start by checking the values of the resistors by trying with the DMM (which might not work well in the assembled circuit) or reading the color bands (which works if you have good colour vision, which I haven't). I would start with the ones that modify the gain most in the circuit: R2, R3, R6, R7, R9, R10. If they are correct, I would check their soldering, as well as the soldering of C4 and the SUS pot (as well as its value).

Cheers, I'll check them out..

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[High Lord]

Checked all resistors,  using DMM unless it was weird then colour chart and an app. All checked out good, checked cap values, all good.  Sustain pot all good.  1n914 all orientated.

I've seen some schematics with 0.68uf for C1? Although I'm guessing that's more a frequency thing as opposed to volume?



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[WormBoy]

A larger value for C1 will let more lows into the circuit. There might be a small difference in volume with different caps, but nothing spectacular. So that's not the reason why volume in your built is low. If everything checks out and there are no obvious soldering problems, I would try audio-probing to see where the sound disappears; that might give a clue where the problem is located. If you look at the schematic, the first opamp stage will boost the signal, the second will boost it even more, and the third will suffer with the SUS pot maxed (and try to boost more, which makes it distort). Again, I never built this pedal, so someone who has actually built it may be able to provide better help ...

[High Lord]

Audio probing was interesting, good idea wormy, I've never used one before although I made one ages ago. Sound was sounding great and crunchy through the first IC, through the sus pot up until about r9, then a duller less trebly and slightly quieter distortion till the end. Interestingly one side of the diode cluster was getting no audio, similarly one side of c6. Could this be it?

All the 914's were measuring ~600(mv?) each anisotropicly.

Cheers again.

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[WormBoy]

At least that narrows down the problem to IC2 and surroundings. Did you use an LM741 for IC2?

You could check again for poor connections or solder bridges on the IC socket, R9, R10, C6 and the diodes. If there is a connection between pin 6 of the IC and pin 2 (you could try testing with the multimeter), that might explain something (at least the volume drop).

Problem might also be the IC itself, so you could replace it and see if that solves the problem.

[High Lord]

Solved!

2..3.... years on the shelf?  Came back to it, checked every available schematic on the www,cursory look at ceramic cap  C6 notice it says 104, its meant to be 150pf, which is like 151? Soo 100000pf instead of 150pf.. Tested it 98.7nf...Checked my bag and its a TAYDA mis-labelling!

Twisted a 100 with a 47, tested at ~146pf, wacked it in and sweet!

Then removed the 100k r15 to ground at the end, slight increase.

So now going back through all my old builds to recheck any 150pf's, britannia, kraken.....

1 bag out of like 200 bags is a pretty good ratio of success I guess, I still rate TAYDA.

Also while trawling through ic muff schems i noticed a few, including analog guru's schematic, had a 4.7uf for C5 instead of beans 1uf,... Reminds me of the fat fuzz factory  switch position, if ya catch my drift [emoji6]

Time to box! [emoji106]

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[WormBoy]

Great that you managed to solve the problem. I personally make a habit of testing each resistor, each cap, and even each diode, with the DMM before soldering it in. It takes a lot of time, but I just hate debugging and desoldering  . Once in a while every supplier makes a mistake ...

The C5 is just a coupling cap. I don't expect that anything larger than 1uF will make an audible difference. The MB version probably suggest the 1uF as it is easy to get in a film version (which has a better audio quality that electrolyte caps).