I destroyed my NAD 3020i, help guys

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#23
Any wire with roughly or more area than the trace will be fine. Something in the range of 1mm ought to do the trick. Do look for burned components, and don't assume that the filter caps are that long for the world your unit is an early one. I owned one in the early 1980s and my recollection is that it already had TO-220 transistors in the output stage. I'd replace the supply caps as a minimum - look for date codes on the large caps as that may give you a clue as to how old this unit actually is.
 
#25
Simple repair, i just soldered a piece of cable for the broken trace.
The amplifier is working again, woohoo.
After almost an hour of playing music everything is ok, except that one capacitor's temp is around 40-43 degrees when it's around 22-33 in all the others.
Do you suggest anything else to check before i put back the covers?
 
#26
Well done, but as recommended replace the 2 big capacitors in the power supply.
I'm replacing all capacitors in my 3020i the Elite capacitors are most likely well past their use by date (Inspection stamp says 76/10/29) so my amp was build in 1976 so is only 36 years old.
Could you please update you profile...
 
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#28
Right now is the amp is driving a set of Aurum Cantus leisure 5SE but I have a set of Polk Audio Ti100 that I was using before and going to put on ebay.
Look at the efficiency of the speaker the higher the better (89/90db is easy to get)
 
#30
As you first said that this was mechanical buzz, not through the speakers, there are only a few options. The usual suspect is the transformer, where ageing, loose laminations start to rattle in concert with the AC supply.

To be more certain where the buzz comes from, you can use an insulated screwdriver as a rough stethoscope, like old-time motor mechanics do to check out various motor ills. Obviously, you take great care with what you are probing and not let slip from the point of mechanical contact. To transfer sound effectively, the surface needs to be a hard, substantial object like the transformer, definitely not components or electrical circuits. IIRC, 3020 transformers varied a little in having assembly bolts which can be tightened somewhat and this can help but not really eliminate mechanical buzz.

In any case, every 3020 owner arriving here (and there are so many) gets advised to replace the main electrolytic capacitors, pointed out earlier. It doesn't matter whether they look brand new on the outside because after 20+ years they won't be, on the inside. They are wet cell devices like batteries and can deteriorate by evaporation of the electrolyte alone. Having checked the date code and replaced these, it sometimes happens that buzzes disappear too. You can buy suitable replacements from CPC or any decent supplier of electronic components.
 
#31
Detach the bottom metal plate. It probably has severe mechanical tension, vibrating together with the transformer. I've seen it on this model before. How this happens - I do not know. When you take it completely loose, it will practically try to fold itself in half. Bend it back - make it totally flat (and make sure it stays that way) - then reattach. Buzz gone!
 
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#34
Noise always becomes mechanical at some point. Ok it is electrical when it is transformed to electricity inside your inner ear....
What I'm trying to say is that if your amp makes this buzz than it is probably caused by transformer. There are few possible reasons how and why.
If you hear it from the speakers than there is something else wrong.
Once again. 246V is quite high and transformer might be close to core saturation point. If you add some dc to it ..than it will buzz definitely.
We have such discussions here already and I've been told by one of very respected members here that so hi voltage is ok and normal and that it is inside specifications and so on and if it exceeds 250V than I have to contact power company to connect me to other tap on the transformer and so on.
If you want to listen your nice vintage amp and you can't sustain buzz than there's been quite few good ideas. From replacing old capacitors(which won't solve mechanical buzz but it is necessary for reliable operation) to mechanical ones like ,,try to loose transformer...
It is nothing magical inside old amp. Go and solve problem. Don't let that it drives you crazy.
Have you checked my link anyway?
Cheers
 
#36
Once again replace the 2 big capacitors in the power supply (you can get them from any Maplin store)
When capacitors dry out they can go high resistance (and short) making the transformer vibrate/buzz.
For a quick test you can disconnect the wires from the transformer to the board and see if the buzz is gone.
Disconnect only the 28/0/28-30/0/30Vac supply.
 
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#39
I'm not familiar with your amplifier but you have to measure it's size and read capacity and voltage from old units. Good think is also to measure leg spacing. Than order something from Farnell. They have some good quality units and it is free next working day delivery if you order minimum 20f.
If you will still hear some noise it is worth to try some sort of DC filter.
Cheers, Taj
 
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