PA Amp - Peavey MP400 - JRC4560DD

[Turnip]

Hi folks,

Just had one of these in, where when I turned up the main volume the sound cut - Came in for No go - supplies seem OK and no burned bits.

Wonder if anyone has thoughts and/or shematic.  Noticed its stuffed full of JRC4560DD Op amps but can't seem to get info on them either, apart from they're a bit like a NJM4560DD and can't find data on them but might buy 'em by the million.

Think there might be some output protection circuit operating, although when re-started - No sound.

Thanks for any ideas - Chris.

Later - discovered that the -ve 15v supply to the front control/Input panel was down to -5.5v and varying slightly  -  The + and - supplies have 15v zeners so replaced the -ve one (ZD2) - problem remained.

Slow biz of isolating everything on the -15v line, problem turned out to be C314 (100nf blue ceramic decoupler) reading 200 Ohms.

[Davy]

Old post I know.

Plenty of SirKits about on the net, here's one.

http://new.eserviceinfo.com/index.php?what=search2&searchstring=peavey+MP+400

Dave

[Turnip]

Hi Dave,

Bit of fun - Gal turned up with the amp + speaker and said her man would phone me later to tell me the problem and give the contact number.

He never did, so still got it under the bench, which is surprising as most chaps with duff Guitar amps want them back within a day for the next gig, or even yesterday at best.

Guess have a cool relaxed dude on hand, and he'll turn up in a year or two - Met 'em before - Chris.