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Nad 3020A developed problems
Nad 3020A developed problems
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Old 14th June 2021, 10:48 PM   #111
Peterbt is offline Peterbt  France
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Thanks all of you for the suggestions and help. I took the front panel off and removed the little lamp so that the switch would be more accessible. Cleaned it and sprayed inside with a 3 in 1 spray which penetrates but evaporates fast unlike Deoxit. I used the paper towel trick as Mooly suggested. Soldered the wires back on reconnected it and lo and behold the sound came right back on after the 5 second muting process. You were 100% right it was the switch. I'll probably have to change it eventually if it acts up again but as you mentioned it 30 bucks is quite a lot for a switch. Pounds, excuse me. Poundy sent this Ebay link for an original NAD switch from Germany but with shipping that was quite pricey too. But they said it was original. Anyway, right now it functions very well, thanks again
Peter
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Old 15th June 2021, 07:25 AM   #112
Mooly is offline Mooly  United Kingdom
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Nad 3020A developed problems
Excellent I'm pleased it worked. It is (was) a very strange fault in all fairness, I can't actually remember anything quite similar tbh.

Enjoy
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Old 15th June 2021, 08:31 AM   #113
Goldie99 is offline Goldie99  United Kingdom
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Yes, a good result - and a lot easier & cheaper than having to change the switch.

Mooly - thanks also for the additional LTSpice examples - I'd been wondering how the switch function could be easily incorporated into the simulation... turning ON was straightforward, turning OFF less so (I haven't used the PULSE option before)
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Old 15th June 2021, 10:09 AM   #114
Mooly is offline Mooly  United Kingdom
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Nad 3020A developed problems
There are loads of ways in LT to do the same thing.

Try this one using a voltage controlled switch.
Attached Images
File Type: jpg Screenshot 2021-06-15 110839.jpg (305.1 KB, 36 views)
Attached Files
File Type: asc NAD FET Muting Drive Circuit revised mod.asc (2.3 KB, 2 views)
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Old 15th June 2021, 10:46 AM   #115
Goldie99 is offline Goldie99  United Kingdom
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Cheers Mooly - looks good. I'll have a play with that once the sun's gone again !

You forgot R549 (390R) by the way - not sure why it's there, except maybe some sort of time constant with C531 ?
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Old 15th June 2021, 11:05 AM   #116
Mooly is offline Mooly  United Kingdom
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Nad 3020A developed problems
I think to protect the switch contacts from dumping the (oh hum) 'large' discharge current from the cap. It would be enough to pit the contacts over many operation... but maybe that would have helped the switch in other ways
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Old 15th June 2021, 05:19 PM   #117
mjona is offline mjona  New Zealand
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Air borne contaminants and moisture can compromise switch contacts. I had a magnetic cartridge go open circuit due to where my record deck was situated. I now have a couple of small gel packs under the lid.
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