Technics sa-616 rising DC voltages and protection mode.

[Carbsandcaps]

I’ve got a technics sa-616 that works fine when first turned on. After a minute or so it will go into protection mode. A few seconds later it will come out. Then after a minute it goes back into protection mode. It will do this 3 times then stay in protection mode until you turn it off for a few minutes. Volume is at minimum.

There is .1v dc on the speaker terminals. Then seemingly out of nowhere the voltage rises sharply to 20v and goes into protection. With a speaker hooked up I can’t hear anything out of the ordinary. I don’t know where this DC voltage is coming from seemingly randomly. I’ve recapped the power supply and amplifier board and then just let it sit. I had it sold and went to test it before I shipped it and good thing I did.

Any ideas are appreciated.

 

[petehall347]

bad solder joint first suspect then a transistor . if both speakers then prime suspect power supply pending looking at schematic for more things in common with both channels

 

[Carbsandcaps]

bad solder joint first suspect then a transistor . if both speakers then prime suspect power supply pending looking at schematic for more things in common with both channels

So on closer inspection it’s only the left channel doing it. It will play and sounds fine then all the sudden, pop and it’s in protection.

 

[Carbsandcaps]

I would think dc offset would be a constant problem. Could a transistor “leak” dc current? I would guess it could only be the outputs.