op-amp: njm4560

[elnaldo]

We need to confirm if Q105 and Q106 are mirrored, so please confirm if the output of the preamp going to C129 (1uF) is coming out of pin 7 in both channels. Or, check if Q101-R123 (differential pair) is connected to pin 5 in both channels, or pin 5 one channel , pin 3 in the other channel.

Also, having just 2 fets, (one double transistor actually), one OPamp, and 3 electrolytcs, I'd replace all 5 parts in one 15' operation. Perhaps you spend 3 days tracing a fail to end replacing one capacitor.

 

[spdf]

Or, check if Q101-R123 (differential pair) is connected to pin 5 in both channels, or pin 5 one channel , pin 3 in the other channel.

I found that diff pair Q101-R123 is connected to pin 6 and Q102-R124 to pin 2

I checked electrolytics with esr meter and changed the bad ones. Not sure how to find these 2sk146-gr fets so I am still hoping they are working fine. I also measured voltages on them.

 

[Alan0354]

We need to confirm if Q105 and Q106 are mirrored, so please confirm if the output of the preamp going to C129 (1uF) is coming out of pin 7 in both channels. Or, check if Q101-R123 (differential pair) is connected to pin 5 in both channels, or pin 5 one channel , pin 3 in the other channel.

Also, having just 2 fets, (one double transistor actually), one OPamp, and 3 electrolytcs, I'd replace all 5 parts in one 15' operation. Perhaps you spend 3 days tracing a fail to end replacing one capacitor.

That might be a better idea. I think I am analyzing this to death. Just do it and get over with it.