Pioneer A-P510 amplifier schematics or service manual

[markiemrboo]

I've been given this amplifier to look at. It is part of a 'mini system', or I think that's what they're called. It is a complete system with an amplifier & preamp, tape deck, tuner, "sound processor" and CD player. In order to get the amp to switch on, you MUST have at least the "sound processor" and tuner connected it seems. They're connected at the back via ribbon cables.

It came to me and I was told it would no longer turn on at all. I didn't bother checking, but looked inside the amplifier unit and saw that the PCB was caked in dust. You couldn't actually see the PCB silkscreen anymore... anywhere! So I dismantled it and cleaned off all the dust with a small paint brush. I then proceeded to try turning it on, and it seems to be turning on alright. Whether it was before is a complete mystery, but I doubt the cleaning did any harm

Whilst cleaning I found out that it uses an STK4172 chip for the amplifier. The chip is HUGE!

I tested it with the DMM and there appears to be < 1mV DC on the outputs, but when I switch to AC it reads about 0.3v. Seems a bit odd to me. I checked the output with the scope and no load, and there is what looks to be about a 1v wave, which looks to be *maybe* 60Hz or so... but get this.... this appears on the output even when the unit is in standby! I guess maybe the standby on it doesn't really switch a lot of stuff off or something.

I have connected a small test speaker however.... and I don't appear to be getting any output from it at all, which I find odd. The wave I previously mentioned isn't to be heard, and selecting the tuner as the source... I still hear nothing.

So I am just wondering if anyone happens to have a schematic or service manual for this amplifier, or even any suggestions where to start looking (I fear this is going to be very difficult without a schematic though).

Thanks in advance,