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Nad 3020a

leesonic said:
There is a replacement power switch and a spark suppressor you can use. Neither of them are cheap, but they will solve the problem. The white and red wires are for muting. They are connected to the separate low current section of the power switch. These wires are connected to the normally closed part of the switch.

Mouser part numbers are :

Replacement power switch 611-NE1839EE
Quencharc for power switch 539-104M06QC100

Lee.
Click to expand...
I have 4020a for spares, so I'm using power switch from there
Can i change capacitor size, and use higher capacity caps? X2 rating?
 
Quencharc for power switch 539-104M06QC100

This is a proper RC snubber, designed for the job, in a single package. Connect this across both terminals of the switch, and make sure (re-wire if necessary) so you are only switching the hot (live) side of the AC. No sense switching the live and neutral, one side will take more than the other, if the snubber wasn't installed.
 
leesonic said:
Quencharc for power switch 539-104M06QC100

This is a proper RC snubber, designed for the job, in a single package. Connect this across both terminals of the switch, and make sure (re-wire if necessary) so you are only switching the hot (live) side of the AC. No sense switching the live and neutral, one side will take more than the other, if the snubber wasn't installed.
Click to expand...
Installed as you said new capacitors as originals. Changed power switch From unused 4020a fm tuner.
Still same problem with pop. And silence for 10 seconds.
Idk. Something is wrong with circuit of these two red/white wires...
And pop maybe related with switch. Because it's was all good without power switch. No pops. I think to try eliminate power switch and install relay? And Only use switch to activate relay's coils?
 
leesonic said:
Pictures of what you've done so far would help.
Click to expand...
I removed snubber. Pop is quiter but still exists. UNTIL i disconnected white/red wires!
If i turn on amp without red/white connected even not a small pop with snubber!!!
If i touch red white wires while amp is playing. It mutes itself. And if i turn off and turn on amplifier (with red white wires disconnected from each other, when it gonna pop, and turn on sound delay appears!!!!)
So the problem is definitely on these red white wires section!
Any ideas??
 
Lee is your expert to help you here. But from my experience (using Lee's notes as guidance) I have now repaired three 3020s (2 x 3020a and 1 x 3020i) and a complete recap of electrolytics seems to resolve all the weird problems you are experiencing (other than the power switch issue). If you want to give new life back to the amp, go to the trouble of doing it and it will last you for many years to come.
 
Have only these right now, if you can specify what you want to see, I could make more photos/videos of that location

 
@leesonic also, is it normal to hear audio output, even with all input buttons depressed? Or to hear sound (I'm talking about barely hearible) on different input, that you have your rca cable connected to, I mean I connect on AUX, and hear a slight sound on tuner/ phono
 
Is this a Euro/UK model? The 3-core mains wire and 20mm fuse would suggest so.

I've restored Euro units that have somehow found their way to the US. I usually connect the neutral wire (white for US color codes) directly to one side of the transformer, and switch the live or hot side (black wire). I also connect the two power poles of the switch together, and put the snubber across these.

The red and white muting switch wires need to go to the front two terminals of the switch, where you have nothing connected at the moment.
NAD power switch wiring.gif
 
@leesonic thanks for an answer. You see I'm from Europe myself. Now it's all disconnected, because waiting for snubber to arrive.
But, white red wires is disconnected because, as I said there would be sound delay as I turn on. There would be no sound for like 10 seconds. So that's why I disconnected the wires. With wires disconnected, the sound appears as soon as I turn on amp.
I tried to trace the circuit from red/white wires. There is resistors, diodes, and transistors. Every of these elements seems to work. Doesn't know where to look for a problem... No cold solder joints as well.
 
GytisBal said:
@leesonic also, is it normal to hear audio output, even with all input buttons depressed? Or to hear sound (I'm talking about barely hearible) on different input, that you have your rca cable connected to, I mean I connect on AUX, and hear a slight sound on tuner/ phono
Click to expand...
Pretty normal on most amps. What you have is bleed-through of the signal. Caused my inductive and capacitive coupling of the signal through to the line input you have selected. (How many times have I been caught out when having repaired an amp, turned things on, hear a signal way down in the dirt, assumed there might be a problem, turned volume up to full, realised I've selected the wrong source, switched over, and blown myself away with massive volume and given myself a heart attack!)
 
dkneyle said:
Pretty normal on most amps. What you have is bleed-through of the signal. Caused my inductive and capacitive coupling of the signal through to the line input you have selected. (How many times have I been caught out when having repaired an amp, turned things on, hear a signal way down in the dirt, assumed there might be a problem, turned volume up to full, realised I've selected the wrong source, switched over, and blown myself away with massive volume and given myself a heart attack!)
Click to expand...
Oh. Okay now it's clear to me. Thanks..
 
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