Author Topic: PA Amp - Peavey MP400 - JRC4560DD  (Read 3920 times)

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PA Amp - Peavey MP400 - JRC4560DD
« on: March 18, 2014,09:57:13 »
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.

« Last Edit: March 19, 2014,09:36:22 by Turnip »

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