NAD3020 mystery (to me)

Calamaro · 3rd April 2009, 06:07 PM

Today my old Nad3020 (fully recapped) suddenly started to play incredibly loud, just one channel, with a kind of hiss. Switched off for half an hour. Then it worked normally but after 20 minutes it began again. I tried a few time with the same results.

Honestly speaking this happened after I modded my cd player, but with the tuner it happens the same so I don't think the two things were related.

I really need help, thanks in advance for any suggestion.

darkfenriz · 3rd April 2009, 07:28 PM

Sounds for me like disconnected feedback node, search for bad solder around feedback node.

Calamaro · 3rd April 2009, 08:25 PM

Ok. But... ehm...

where is it?

dave_gerecke · 3rd April 2009, 11:19 PM

Hello Calamaro, I can't point out where the feedback node might be, but if you don't have a schematic, drop me an email with your email address and I can send you a PDF of the schematic. If your email will allow larger files, I can even send a PDF of the service manual, but it is around 12megs.

Peace,

Dave

Calamaro · 4th April 2009, 12:47 PM

Hello Dave, thank you for your offer. Actually I have schematics but I think I'm still not able to identify the thing.

analog_sa · 4th April 2009, 02:14 PM

R661, 470R, connected between the speaker side of the thermal fuse and the input transistor emitter. If this resistor is intermittent or a solder joint is bad the gain will be determined by R635 and be several times bigger.

Calamaro · 4th April 2009, 04:40 PM

This is the ideal reply. Thank you so much, I'll definitely check it.

planet10 · 4th April 2009, 06:24 PM

Quote:

Originally posted by analog_sa
... or a solder joint is bad...

the quality of construction of the 3020 does lead to bad solders. There are a couple place oin the reg circuit where lack of heatsinking makes it even worse.

Service Manual (early version)

dave

3rd April 2009, 06:07 PM	#1
Calamaro diyAudio Member Join Date: Mar 2008	NAD3020 mistery (to me) Today my old Nad3020 (fully recapped) suddenly started to play incredibly loud, just one channel, with a kind of hiss. Switched off for half an hour. Then it worked normally but after 20 minutes it began again. I tried a few time with the same results. Honestly speaking this happened after I modded my cd player, but with the tuner it happens the same so I don't think the two things were related. I really need help, thanks in advance for any suggestion.

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3rd April 2009, 07:28 PM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	Sounds for me like disconnected feedback node, search for bad solder around feedback node.

3rd April 2009, 08:25 PM	#3
Calamaro diyAudio Member Join Date: Mar 2008	Ok. But... ehm... where is it?

3rd April 2009, 11:19 PM	#4
dave_gerecke diyAudio Member Join Date: Dec 2007 Location: Vermont	Hello Calamaro, I can't point out where the feedback node might be, but if you don't have a schematic, drop me an email with your email address and I can send you a PDF of the schematic. If your email will allow larger files, I can even send a PDF of the service manual, but it is around 12megs. Peace, Dave

4th April 2009, 12:47 PM	#5
Calamaro diyAudio Member Join Date: Mar 2008	Hello Dave, thank you for your offer. Actually I have schematics but I think I'm still not able to identify the thing.

4th April 2009, 02:14 PM	#6
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	R661, 470R, connected between the speaker side of the thermal fuse and the input transistor emitter. If this resistor is intermittent or a solder joint is bad the gain will be determined by R635 and be several times bigger.

4th April 2009, 04:40 PM	#7
Calamaro diyAudio Member Join Date: Mar 2008	This is the ideal reply. Thank you so much, I'll definitely check it.

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