Peavey 6505+ 112 Combo - No Input Signal

[egemme28]

Hey guys,

Long story short - getting power/signal when I run my guitar through the FX return, but no sound when I plug into the Input. Replaced preamp tubes - didn't solve the problem. Fuse looks to be in good condition.

Any ideas?
-Eric

[Jazz P Bass]

Have you tried a jumper from Send to Return?

[egemme28]

I have not, but the power/fx return seems to work fine for the clean signal

[alexradium]

are the first 4 preamp tubes lightin up?

[shortcircuit]

Here is the schematic, hope it helps
Peavey-6505PLUS-112-Schematic.pdf

[J M Fahey]

I have not, but the power/fx return seems to work fine for the clean signal

Ok, pleased *do* the test and post results.

[Danglin' Fury]

Not to hijack a thread or anything, but I have this problem right now and my first 4 preamp tubes are not lighting up... and I can play through the effects return. Pretty sure a diode crapped out... gonna take em out and measure them...if it's not that then its cap checking time.. at least it's a very straightforward and easy circuit to replace... I have 6 cap replacements if I need em...

[Enzo]

Please just start a new thread.

Diodes and caps? The 12AX7s are in parallel, so I'd be looking for an open R82. I'd verify there is something like +6v leaving D24, D18. And verify AC between PDCH1 and PDCH2. Between them, NOT to ground.

[The Dude]

...... at least it's a very straightforward and easy circuit to replace......

It's also a very straightforward and easy circuit to troubleshoot. Instead of pulling and replacing components, take a few voltage measurements (as Enzo said). Is there AC coming out of the transformer? Is it getting to the rectifier? Is there DC out of the rectifier? Is it getting past R82?

[Danglin' Fury]

I took voltage measurements unloaded and loaded (preamp tubes installed)...2 diodes in the rectifier were bad... replaced all diodes in the rectifier and all is well...