Hi Kaibosher, I have an identical model to yours on my bench right now. Did you ever find, or produce, an accurate schematic for it?
The condition of mine can only be described as "toasted"...the board around the outputs is completely brown. I suspect, from reading the excellent info in the "Repair briefs 5" link, that it has the oscillation fault, curable by adding decoupling caps. But there are several Zeners on this board, and I'm not quite sure where to put them.
The previous repairer gave up and handed it back to the customer with the warning "whatever you do, don't plug this bloody thing in!" - But I do enjoy a challenge now and then!
The condition of mine can only be described as "toasted"...the board around the outputs is completely brown. I suspect, from reading the excellent info in the "Repair briefs 5" link, that it has the oscillation fault, curable by adding decoupling caps. But there are several Zeners on this board, and I'm not quite sure where to put them.
The previous repairer gave up and handed it back to the customer with the warning "whatever you do, don't plug this bloody thing in!" - But I do enjoy a challenge now and then!
Hi, glad this info was somewhat useful!
I had a rough sketch of the driver and output stage, but it needs refining. I'll try dig it out.
Capacitors go from each rail to ground after the last series resistor on the rail. A convenient place for this is across the last zeners on the rail, at the preamp section.
My amp is stored away. If you send me a pic of the amp board I can circle the right zeners.
I got my amp sort of working, up to the point of putting those capacitors in place so I can't verify it works, but it definitely makes sense. (I ran out of time and motivation, but will open it again soon!)
I made a bucking transformer recently to run this amp at a lower voltage permanently. This amp had a 220V mains transformer, getting 240V here. The rails are running to hot I think.