Peavey Deuce VT - 2nd Channel (Effects) not working!

[bw1985]

Hi all,

Hoping for a little advice here on where to start with this Peavey Deuce VT amp I am working on. For some reason, the 2nd channel (Effects) has barely any output at all. You can still hear the guitar signal and effects working, but barely any output. The first channel (Normal) appears to be working fine and sounds fantastic! Full output, and functionality.

I have tried using both the Mixer feature with the pedal and plugging directly into the 2nd channel inputs and have the same results.

All power tubes tested strong. Any advice would be appreciated!

Thanks,
Brian

[glebert]

Are you using a footswitch? I would check voltages on pin 2 of U17 and U18. Do you have a scope that you could trace signal?

[Enzo]

Where to start? Start at the input. Apply a signal there, and trace it through the channel. See where it disappears.

[bw1985]

Are you using a footswitch? I would check voltages on pin 2 of U17 and U18. Do you have a scope that you could trace signal?

The behavior seems the same with and without the footswitch. I can check those voltages, and I do have access to a scope I could try.

[bw1985]

Where to start? Start at the input. Apply a signal there, and trace it through the channel. See where it disappears.

For sure, I was just wondering if this was an issue other users have perhaps come across. Definitely have isolated the issue to the 2nd channel preamp circuit.

[Enzo]

Of course we have encountered it: amplifier with one channel not passing signal. But it can be anything in the channel. DO I have favorite suspects? Sure, but bad op amp? Bad TL604? bad control? Bad solder somewhere? Broken trace? There is no reason to think the exact same fault in mine will be the fault in yours. We could make up a list of what everyone has found wrong with a channel for this symptom. And we could check each of those things. Or we can just shoot the signal through the amp and see where it goes. We are more likely to learn something that way, plus it is likely faster.

[bw1985]

Of course we have encountered it: amplifier with one channel not passing signal. But it can be anything in the channel. DO I have favorite suspects? Sure, but bad op amp? Bad TL604? bad control? Bad solder somewhere? Broken trace? There is no reason to think the exact same fault in mine will be the fault in yours. We could make up a list of what everyone has found wrong with a channel for this symptom. And we could check each of those things. Or we can just shoot the signal through the amp and see where it goes. We are more likely to learn something that way, plus it is likely faster.

Well said, sir! I will do some digging and report back to what I find! Thanks again for the advice.

[bw1985]

Are you using a footswitch? I would check voltages on pin 2 of U17 and U18. Do you have a scope that you could trace signal?

Sure enough the issue was with U17 and U18. One of the chips was missing a voltage on Pin 7. Swapped them and now the normal channel is quiet. Thanks all!