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Nad 3020A developed problems
Nad 3020A developed problems
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Old 14th June 2021, 09:56 AM   #91
Goldie99 is offline Goldie99  United Kingdom
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I'd have hoped for a better result using the other pair of terminals, but it is what it is.

The original Alps switch is long obsolete, but does occassionally turn up on the usual auction site, normally well over-priced. The following is an example of a slightly older version of the same switch - which I think may have a lower mains current rating than yours, but I'm not sure (?): Alpes SDU3P Power Switch TV-3 - NAD realiste Marantz Concept 16.5 Recepteur Sanyo | eBay
The only suitable 'new' replacement switch that I'm aware of would be the following: Commutateur: ES0210 INTERRUPTEUR DE RESEAU / 6A / 250V = KONIG 6571 / 16571 / CRP2147 / CBP3011... (full specs are available at Mouser - https://www.mouser.co.uk/ProductDeta...GIQgtl4FQ0uQ==). This switch is certainly suitable, and is almost a drop-in replacement - you would need to transfer the original NAD switch mounting 'plate', which is fiddly but straightforward to do, and reposition the wiring a little (it's physically smaller than the original NAD switch).
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Old 14th June 2021, 12:03 PM   #92
poundy is offline poundy  United Kingdom
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Nad 3020A developed problems
i take these apart and clean them, and quite successfully.Ive managed to take apart every switch in those amps and clean the contacts, they are on little 'u' shaped sliders.They are very fiddly, but it is possible.
Ive tried getting alternatives but the probelm i found is the distance from the switch flange to the tip of the knob stem, they tend to be close, but not exact, and this ends up making the switch protrude from the front casing.
quite often, because the plastic is quite brittle, the stems snap off, so i remove them, dril out the stem and switch with a 1mm drill and glue the 2 parts back together with a cut to size panel pin glued in-works a treat.

give it a go though you might just get lucky.

Last edited by poundy; 14th June 2021 at 12:05 PM.
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Old 14th June 2021, 12:11 PM   #93
Peterbt is offline Peterbt  France
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Thank you again for helping me on this.


Now with the white wire disconnected the amp sounds like before. No thumps or bangs on start up. There is a very short growl for a couple of seconds, that's it. When I turn it off it goes silent immediately. As for cleaning the switch the best would be to take it out as there isn't much room there to get to it. But that's a lot of work having to desolder then re solder all those wires etc. I've already tried to clean it a little but over the decades it has accumulated a lot of dust inside the amp which turns into grime. Perhaps I should just buy a cleaner that penetrates and evaporates immediately. I think 3 in 1 does something like that but not sure. Deoxit tends to lubricate more which produces grime too. It doesn't evaporate.
As for that resistor, seems pretty difficult to get such a high value that's small as well
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Old 14th June 2021, 12:25 PM   #94
Peterbt is offline Peterbt  France
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Quote:
Originally Posted by Mooly View Post
Firstly Peter... how do you feel the amp behaves with the wire left disconnected? I was just thinking a bit more on this.

Are there any problems with excess noises (bangs, thumps etc) as you turn the amp on and off with the mains switch and I'm actually thinking more of noises at switch off now.

The resistor I suggested would not actually help much with noise at switch off. When you turn the amp off the switch connects the mute circuit to the negative supply and it relies on that negative supply lasting long enough (as the caps discharge) to hold the amp in mute while the main amplifier power supply caps also discharge and the whole amp then stops functioning.

I have some other ideas on the switch itself. You say it is very dirty. How confident are you of putting some paper towel under and around that first part of the switch, then hold the amp vertically on its front and give that switch area a good clean with your spray. Work the switch on/off many many times and use the paper to absorb the gunge. Flood that part of the switch with cleaner but keep the amp vertical to stop it running into the mains area of the switch.

(By disconnecting the switch and also you confirming the voltage is correct on D507 we have proved beyond doubt that leakage is the problem)



Just read your post, thanks. So the resistor helps only on start? At this point it doesn't make any noise on switch off. I'll try your cleaning suggestion but I'll get a different cleaner. As I've said I think the Deoxit produces even more gunk mixing with the dust.
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Old 14th June 2021, 12:41 PM   #95
Mooly is offline Mooly  United Kingdom
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Nad 3020A developed problems
If you are happy with the overall result of leaving it off then that is a valid fix for you

The resistor would have ensured the cap discharged when the amp was off and so it would get the full mute effect at power on... but you say it growls

It is possible that the mechanics of the switch are such that the contacts of the mains section and the mute section are not exactly timed together... by design. So as you press it on the mains voltage might be applied before the mute contacts open.

If you can remove the switch, even if you don't unsolder it, then it would be worth saturating that front part with cleaner.

Don't use anything other than a recognised switch cleaner, some products can actually attack and soften plastics over months and years, a problem I know only to well from working in the repair trade.
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Old 14th June 2021, 12:42 PM   #96
poundy is offline poundy  United Kingdom
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Nad 3020A developed problems
if you dont have any joy with the switch or getting a replacement, im quite happy to take it apart and clean it up for you if you send it to me
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Old 14th June 2021, 12:57 PM   #97
Peterbt is offline Peterbt  France
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Thank you very much, I'll sure consider it. I'll try cleaning it first as Mooly suggested it then if no good I'll take it out and re clean it. There is the replacement option too but I am not too sure about that especially if you have to drill and glue but I'll check the Ebay or the other source as Goldie suggested it. If the amp functions as is I'll probably just let it be after some cleaning efforts.
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Old 14th June 2021, 01:05 PM   #98
Mooly is offline Mooly  United Kingdom
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Nad 3020A developed problems
If you clean it then operate the switch dozens and dozens of times very quickly to work the cleaner into the thing. Use paper towel to absorb the run off.
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Old 14th June 2021, 01:20 PM   #99
Peterbt is offline Peterbt  France
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Thanks a million for all the help. At least I have my music back. Before I had just silence out of the amp. The problem I have is that I am a lot better fixing or finding the source of a mechanical malfunction than an electronic one. So thank you all again
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Old 14th June 2021, 01:24 PM   #100
Mooly is offline Mooly  United Kingdom
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Nad 3020A developed problems
You're welcome, and it has been an interesting problem. Not the usual sort of thing.

Lets see what the cleaning does
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