peavey pv2600 dc kick on power off

[31474]

hi guys, longtime lurker on this forum but i dont post alot.
but this time i need your help!

im currently performing repairs on a peavey pv2600, it originally had a blown channel (channel b) so i replaced all the blown parts (so many!) and now that channel works great!

but now another issue has been found, the channel A works good and passes audio, but when i shut the amplifier off, about -18vdc gets thrown on the output! and now its giving me a headache, i have tried to follow the signal path to see if that dc kick comes from, it seems to come before the power transistors. the kick is there wether the channel volume is up or not.

have any of you guys ever see this problem?
i havent played with bias (because its not mentioned in the schematics)
here you can download the schematics :PEAVEY PV-2600 Service Manual free download, schematics, eeprom, repair info for electronics

any help will be welcome!

 

[ishiru]

looks like bias isn't the problem.what about the VAS and other things?.they might be faulty even not broken yet 🙂

or use a protection circuit? 😀

 

[31474]

looks like bias isn't the problem.what about the VAS and other things?.they might be faulty even not broken yet 🙂

or use a protection circuit? 😀

im not too sure what vas means, could you lighten me up ?

 

[JonSnell Electronic]

Do both channels do that? If they do, it is probably due to the rails collapsing and when they get less than 20Volts the output stage latches. I think you will find this is normal for a budget Peavey amp. There is no isolation relay contact stopping this from happening. If you are worried, fit an AC relay, that way the contact will Open as soon as the mains is switched off.

 

[31474]

only channel A does this problem, channel b does not. i know its not normal, i have a pv2600 at work and it definatly doesnt do that