Help debugging a weird (to me) problem with a circuit

[pgodfrin]

Greetings oh esteemed Etchers...
Been out of the loop for a while - decided to give this one a whirl:
https://www.freestompboxes.org/viewtopic.php?t=5592&sid=9d4ea6a30be719cd423cbd0cc9632ebb

Got a prototype soldered up and it's doing this weird thing, where it's reacting to the input volume. For example, I turn the guitar pot up to 10, the sound cuts out, but at 8 it works. It also fades in and out...

Something tells me it's a cap issue, but I simply don't understand what the issue could be nor where to start. While waiting for suggestions, I'll review the schematic for mistakes.

Any thoughts? Dazed and confused,
phil

[jimilee]

Check your soldering and post pictures.


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[pgodfrin]

photos! I had a little soldering mishap, in the middle there, but there's continuity...

[madbean]

First I'd check that your pull down resistor is the correct value. What you describe could be an input impedance issue. Then I would check the IC voltages.

[pgodfrin]

Thanks, I will check the pull down (of course I have to find out what that is exactly ).
Insofar as the IC voltages, I know one pin is at 9v and another at 4.5 ish), but I don't know what the others should be.
Clearly a learning opportunity.
regards,
pg

[Haberdasher]

That TL074 is a quad, so it should probably be something like this
1 - 1/2 Supply
2 - 1/2 Supply
3 - 1/2 Supply (Sometimes might be a little lower)
4 - Voltage Supply
5 - 1/2 Supply (Sometimes might be a little lower)
6 - 1/2 Supply
7 - 1/2 Supply
8 - 1/2 Supply
9 - 1/2 Supply
10 - 1/2 Supply (Sometimes might be a little lower)
11 - 0V (GND)
12 - 1/2 Supply (Sometimes might be a little lower)
13 - 1/2 Supply
14 - 1/2 Supply
Check out the data sheet and compare it to your schematic. You'll probably see what's going on pretty quickly.

[pgodfrin]

Will do - thanks very much. Like I said - a learning opportunity.

[pgodfrin]

Well hot dog! Thanks for your advice folks, the schematic was an unholy mess. Got that straightened out and it works! The tip about the voltages proved to be spot on (and probably a standard answer, lol).
Cheers...
pg