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Marantz 2230 STUMPED

Posted: Tue Apr 26, 2022 4:38 pm
by mikefc
I decided to take a break and reach out for help here at AK. Sometimes when you get in a rabbit hole of troubleshooting you can really become blind, a new perspective would be greatly appreciated. I am repairing an old Marantz 2230, it was in bad shape with many issues, all of which are taken care of now except for the right amp PCB problem. The 29vdc stands at 28 with no load. Under load it delivers nice amplification until about half volume when the supply begins to drop precipitously. Clipping begins when the voltage drops to 22vdc. (R765 needs to be all the way up to even get to 28v.)

All caps have been tested out of circuit and seem OK, all electrolytics have been replaced. All transistors have been replaced. I substituted 2sc2235/2sa965 for H753/754 , H755/756 are NTE 128/129 ; Is this a mistake?

H001 and 002 tested ok but I still swapped left to right to see if the problem followed, it did not. The output cap tested 2200uF ( I was thinking it may be leaking? )

by the way, the schematic calls for 66.5vdc , I only have around 62 but the left side is perfect.

What am I missing? It seems to me that as soon as current is demanded, a component is leaking to ground. Active devices seem to do what they need to but are being starved for supply.