I'm toying with the possibility that the power amp stages are responsible for the power-on pop.
Referring to left channel, I believe VR5 is used to trim output to 0VDC.
There should be 0mV across R601, R603, and R631 if the associated electrolytic capacitors have low leakage. To my eyes, the polarity of C603 looks backwards. But in the right channel, it is C602 that looks backwards.
Actual installed polarity deserves scrutiny, IMO.
Referring to left channel, I believe VR5 is used to trim output to 0VDC.
There should be 0mV across R601, R603, and R631 if the associated electrolytic capacitors have low leakage. To my eyes, the polarity of C603 looks backwards. But in the right channel, it is C602 that looks backwards.
Actual installed polarity deserves scrutiny, IMO.
Hi BSST
re: 21 (luckythedog #5), yes, if I remove the links between "Pre-Amp out" and "Normal In" I get the normal slight power-on sound (what I'd describe as a gentle "whuuum", even with volume turned right down), if I put them back I get the loud pop.
I got the service manual from https:{slash}{slash}www.eserviceinfo.com{slash}downloadsm{slash}248559{slash}NAD_3020.html - little nervous getting stuff from "free" download sites and then passing it on to other people - if you want to get it from there the Russian bit on the linked page appears to translate as "numbers".
The caps all "look" okay (I wouldn't expect to see much different if any had failed in a less than spectacular way), apart from C518 (on the pre-amp) that has what looks like a drop of solder and maybe a bit of "fluff".
re: 21 (luckythedog #5), yes, if I remove the links between "Pre-Amp out" and "Normal In" I get the normal slight power-on sound (what I'd describe as a gentle "whuuum", even with volume turned right down), if I put them back I get the loud pop.
I got the service manual from https:{slash}{slash}www.eserviceinfo.com{slash}downloadsm{slash}248559{slash}NAD_3020.html - little nervous getting stuff from "free" download sites and then passing it on to other people - if you want to get it from there the Russian bit on the linked page appears to translate as "numbers".
The caps all "look" okay (I wouldn't expect to see much different if any had failed in a less than spectacular way), apart from C518 (on the pre-amp) that has what looks like a drop of solder and maybe a bit of "fluff".
Attachments
Pop from the preamp is probably an easier problem to resolve than a pop from the power stage. IIRC, your preamps do not use the JFET muting circuit?
Do both channels exhibit the same pop behavior?
Do both channels exhibit the same pop behavior?
That's right, no JFET muting circuit.
Pop only on right channel (see message #12 above). C518 is on the right channel.
As has been mentioned by Anibal #4, it's probably worthwhile doing a complete re-cap while I'm about it (if one's gone, the others will be going...).
Pop only on right channel (see message #12 above). C518 is on the right channel.
As has been mentioned by Anibal #4, it's probably worthwhile doing a complete re-cap while I'm about it (if one's gone, the others will be going...).
Hi hrp
Apologize for desturbing the past, but
where there an end to the story about your popping NAD 3020?
Thank you in advance. Tonny
Apologize for desturbing the past, but
where there an end to the story about your popping NAD 3020?
Thank you in advance. Tonny
Ive done many of these and most of the time it is the switch itself.remove it and give it a good clean, then replace all 3 caps to 100v, that should do it.
You should be able to test it by shorting out the S/D, see if the pop goes away.
If its not a 'A' but a first series 20 it has no muting. Appologies if ive repeated anything someone has already stated
You should be able to test it by shorting out the S/D, see if the pop goes away.
If its not a 'A' but a first series 20 it has no muting. Appologies if ive repeated anything someone has already stated
Hi.
Which 3 capacitors are you thinking about? The two in the “normal” pre-input and the large one in the first amplifier stage?