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Old 29th September 2012, 06:47 PM   #31
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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!

Last edited by Coconuts 500; 29th September 2012 at 06:49 PM.
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Old 29th September 2012, 07:33 PM   #32
Tajzmaj is offline Tajzmaj  Slovenia
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I'm not familiar with your NAD but if there is any mains voltage selector set it to 240 or 250V. Mains is really high in the UK. Check this out too.
Cheers
dc filter
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Old 29th September 2012, 10:48 PM   #33
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Input voltage is 246V.
It is electrical noise, not mechanical.
The amp is connected on a 4 way safety multisocket adapter, i'm gonna connect it directly to the wall's socket.

Driving me nuts...
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Old 30th September 2012, 02:31 AM   #34
Tajzmaj is offline Tajzmaj  Slovenia
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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
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Old 1st October 2012, 08:29 PM   #35
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Default service manual

You can download 3020i service manual from this site
NAD 3020 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
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Old 3rd October 2012, 01:10 AM   #36
RS232 is offline RS232  United Kingdom
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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.

Last edited by RS232; 3rd October 2012 at 01:15 AM.
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Old 3rd October 2012, 01:13 AM   #37
Tajzmaj is offline Tajzmaj  Slovenia
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Agree.
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Old 3rd October 2012, 11:18 PM   #38
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You were right guys,the noise was mechanical also but i could not completely eliminate it.
I'm gonna replace the capacitors as you suggest
Can you tell me their specs?

Cheers
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Old 4th October 2012, 01:18 AM   #39
Tajzmaj is offline Tajzmaj  Slovenia
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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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Old 7th October 2012, 12:54 AM   #40
RS232 is offline RS232  United Kingdom
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The schematic shows 4700uF x 35V but you can go up to 10000uF
I put in some Sanyo capacitor I had from another project and they are 6800uF x 50V and a perfect fit.
A good choice are the Panasonic ones and they are cheap.

Ric
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