Peavey PV-2600 Amp problems

[juko]

I have a PV-2600 amp that had channel A blown- I replaced all the outputs & protection resistors, a few burnt resistors & shorted diodes to get it powered back up, but now the DDT & Signal lights stay on solid for Channel A even with no input connected & no speakers connected. I have gone over the schematic & compared to the working B channel, but cannot find anything else shorted/open. Any help would be great!

Also, I have tried disconnecting the input board to see if the problem was there, made no difference. Also the fuses have never blown- even when the outputs shorted.

[Enzo]

Turn it off. Measure resistance directly across the output terminals. Is it shorted?

Whenever you rebuild a blown up PV amp, check for a burnt up protective triac crowbarred across the output.

Here is a paper on the protection circuits.

[juko]

No, the output does not read shorted- matches the good channel. I checked the triac against the good channel also, & it reads the same. When I first got this for troubleshooting, I plugged it in & it blew Q102, Q103, Q104, Q105, & some resistors- I thought this was a bit odd considering it hadn't been used in a few years due to it burned out.

[juko]

Update: found an open 4.7 ohm resistor, replaced that & powered back up to troubleshoot & all 4 triacs blew (Q108-Q111) along with a shorted diode (CR125).

[Enzo]

Q108-111 are not triacs, they are bipolar transistors, in this case your output transistors. A shorted CR125 would be extremely rare.

If your burnt 4.7 ohm resistor was R125 or R134, then it is highly likely that the nearby Q104,105 was bad at some point to cause it. Drivers Q106,Q107 are also highly suspect.

If you don;t have a variac, look up "light bulb limiter," make one, and use it. And until we have the amp working, do not connect a speaker to it.

[juko]

The 4.7 ohm was R125, & yes, Q104, 105, 106, & 107 were all exploded when I got the amp & have all been replaced. I'm not going to have time this weekend to any more on it, but will get back to it on Monday, & I will make a light bulb limiter- wish I would have earlier!

[Enzo]

Do not assume all the new parts you have installed are still good. Some could have ben damaged the instant you applied power. Always go back and retest them.

[ddelectrical]

Dead link!

[Enzo]

If no one reposts it here, you can always contact customerservice@peavey.com for it.

[Jazz P Bass]

Here you go:PV2600.zip

[ddelectrical]

Thank you.

Thank you to my bass guitar! Huh. How does that work? Owned a white P Jazz special since '88! LOL!