Just picked up a very nice looking P2200, everything works except the output of the right channel is 1/3 that of the left. This is what looks to me to be all original, I’m going to replace all the electrolytic caps including the power supply caps and that one tantalum, clean up any corrosive glue, check solder joints then i’ll slowly power it up as I did when I first got it with a variac and a DBT to limit current so I can check bias. DC offset is similar and very low on both channels 12-15mv.
I know my limitations, I’m a pretty decent troubleshooter but I was wondering if you folks could offer up some suggestions as to where to start so I don’t chase my tail for too long, lol. I’m interested in assistance from anyone but hoping @anatech might chime in if not too busy.
Thanks one and all in advance for any assistance you can provide.
Don
I know my limitations, I’m a pretty decent troubleshooter but I was wondering if you folks could offer up some suggestions as to where to start so I don’t chase my tail for too long, lol. I’m interested in assistance from anyone but hoping @anatech might chime in if not too busy.
Thanks one and all in advance for any assistance you can provide.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Don
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Here it is apart for cleaning and service.
I think I will start work on the weak channel with a bypass of the pot, unlikely but I have to start somewhere.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I think I will start work on the weak channel with a bypass of the pot, unlikely but I have to start somewhere.
Nice amp... only 3 gain stages and no unobtanium mosfets!!! I have a service manual, 2MB, so PM me if you need it.
You'll need tone generator and oscilloscope + read and learn a bit how to trace the signal from input towards the output; the fact the other channel works okay should help you a lot
Good luck,
Nick
PS: your links to photos are a no go
You'll need tone generator and oscilloscope + read and learn a bit how to trace the signal from input towards the output; the fact the other channel works okay should help you a lot
Good luck,
Nick
PS: your links to photos are a no go
Thank you Craig. I bought an amp yesterday, did a quick check and didn't notice difference in gain/lack of low frequencies in one channel as it had various problems with broken TRS inputs, RCA 3.5mm cable failing when I was unplugging the darn thing and the fact I brought a small speaker with me to test (didn't notice the difference in the bass response).
1) Checked the Rpots and didn't find much of an issue (will need to take them apart and clean, the one on the right has higher resistance at no attenuation setting, but I won't use it in that range anyway).
2) found this thread, took the amp apart and noticed bubbled C106. Funny enough I didn't know which one was C106 and there are 2 versions of service manual. Good thing I have download both manuals. One has C106 and the other one doesn't... (perhaps different service manual for each channel). The cap won't even register on DMM for capacity check.
Anyhow swapped that guy with Nichicon 50V 470uF. Good thing I had a few laying around and then did the same thing on the other channel to match (though that cap was within spec).
Amp is up and running. Need to spend more time cleaning this guy and recapping it later.