Another NAD 3020

jerryo · 30th March 2009, 06:21 AM

I have just pulled out an old 3020 from a shelf where it has been hiding for awhile.
On switch on there is a thump and crackle which seems to be quite common, but that quickly dies away.(caps charging)?
Both channels work but one set of speaker outputs has some voltage across them which cannot be adjusted. I tried both trim-pots; VR6 is fine but VR5 has no effect from full left to full right.
Please can someone point me in the right direction for diagnosis.
Would like to repair otherwise its going for spares or repair on ebay.
Many thanks.

planet10 · 30th March 2009, 07:02 AM

Do you have a copy of the service manual?

dave

reddish75 · 30th March 2009, 08:29 AM

the thump on switch on is normal with these amps, as there's no protection circuit.

the crackle is the power switch i have replaced many of these, when replacing also replace the capacitors on the switch.

this is quite an old amp, so other things inside will need replacing most if not all capacitors gone, while replacing these is not expensive, i would recommend useing all the same make on all but the signal caps, for this you will need the service manual or schematic.

the reason why one of your pots won't adjust is that it is broke, you will not find anys pots this big, so find the biggest you can and extend the legs so it does fit, the value of these pots is 20k.

something else thats worth noting, if the voltage on the terminals is around 5v and you have'nt replaced the the capacitors on the board, its a good chance that the 1000uf 6.3v cap has gone in that channel.

and finally if this amp hasn't been looked at for a few years or ever, the idle current will need adjusting, again instructions for this are in the service manual.

planet10 · 30th March 2009, 08:54 AM

Quote:

Originally posted by reddish75
you will need the service manual

http://homepage.mac.com/planet10/man...viceManual.pdf

dave

jerryo · 31st March 2009, 07:24 AM

Thanks for the quick replies, very good of you.
Planet10, I have tried the link to the service manual but it just comes up with a blank page. I will try again but if that does not work do you know if there is another site that has it?
Reddish75, the amp is showing 0.648 volts across the speaker terminals of one channel if that helps in any way. I thought about doing a cap re-placement some time ago, that`s when it went on the shelf so maybe it is time. What about reducing the switch-on thump...........any ideas (simple ones).....what about a couple of correctly rated thermistors on the supply rails to the power amp section before or after the fuses?
Thanks again.

planet10 · 31st March 2009, 07:59 AM

Quote:

Originally posted by jerryo
Planet10, I have tried the link to the service manual but it just comes up with a blank page.

Works fine here. Have you tried to download it to your desktop or are you trying to open it in your browser?

dave

reddish75 · 31st March 2009, 09:22 AM

the new switch and capicitors across it should reduce the thump, the only way to remove it completly is buy or build a speaker protection relay, as for the voltage it could be just down to the broken pot, replace this part before you do anything else just to see if it is.

thanks

chris

jerryo · 31st March 2009, 01:06 PM

Hi planet10, have got it now so thanks again. Cheers dude.
Hi reddish 75, there is some choice of trim-pot from Farnell; would a rating of 0.5w be OK? it does not give a figure on the parts list.

reddish75 · 31st March 2009, 11:53 PM

i use these you can bend the back legs to fit without extending then, so just the front one to do!

http://uk.farnell.com/bourns/3329h-1...20k/dp/9354140

jerryo · 1st April 2009, 05:40 AM

Hi reddish75, those are the ones that I was looking at myself. I will do both of them (vr5,vr6) of course.
The service manual from planet10 gives a different layout to the amp that I have and has another trim-pot (vr7) for setting the output display led`s. I need to have a close look to check whether the instructions given for setting the idle current still hold true by using R653,R654.

30th March 2009, 06:21 AM	#1
jerryo diyAudio Member Join Date: Jun 2007	Another NAD 3020 I have just pulled out an old 3020 from a shelf where it has been hiding for awhile. On switch on there is a thump and crackle which seems to be quite common, but that quickly dies away.(caps charging)? Both channels work but one set of speaker outputs has some voltage across them which cannot be adjusted. I tried both trim-pots; VR6 is fine but VR5 has no effect from full left to full right. Please can someone point me in the right direction for diagnosis. Would like to repair otherwise its going for spares or repair on ebay. Many thanks.

30th March 2009, 07:02 AM	#2
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Do you have a copy of the service manual? dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
NAD 3020 drivers	wuffwaff	Solid State	36	17th January 2009 09:45 AM
nad 3020 problems	reddish75	Solid State	0	19th May 2008 08:03 PM
NAD 3020 problem	vubkevin	Solid State	16	11th December 2007 01:08 PM
NAD 3020 hum	rigadig	Solid State	13	31st May 2004 09:33 PM
NAD 3020 problems	Neopsp	Solid State	2	17th May 2002 02:34 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

30th March 2009, 08:29 AM	#3
reddish75 diyAudio Member Join Date: Aug 2006	the thump on switch on is normal with these amps, as there's no protection circuit. the crackle is the power switch i have replaced many of these, when replacing also replace the capacitors on the switch. this is quite an old amp, so other things inside will need replacing most if not all capacitors gone, while replacing these is not expensive, i would recommend useing all the same make on all but the signal caps, for this you will need the service manual or schematic. the reason why one of your pots won't adjust is that it is broke, you will not find anys pots this big, so find the biggest you can and extend the legs so it does fit, the value of these pots is 20k. something else thats worth noting, if the voltage on the terminals is around 5v and you have'nt replaced the the capacitors on the board, its a good chance that the 1000uf 6.3v cap has gone in that channel. and finally if this amp hasn't been looked at for a few years or ever, the idle current will need adjusting, again instructions for this are in the service manual.

31st March 2009, 07:24 AM	#5
jerryo diyAudio Member Join Date: Jun 2007	Thanks for the quick replies, very good of you. Planet10, I have tried the link to the service manual but it just comes up with a blank page. I will try again but if that does not work do you know if there is another site that has it? Reddish75, the amp is showing 0.648 volts across the speaker terminals of one channel if that helps in any way. I thought about doing a cap re-placement some time ago, that`s when it went on the shelf so maybe it is time. What about reducing the switch-on thump...........any ideas (simple ones).....what about a couple of correctly rated thermistors on the supply rails to the power amp section before or after the fuses? Thanks again.

31st March 2009, 09:22 AM	#7
reddish75 diyAudio Member Join Date: Aug 2006	the new switch and capicitors across it should reduce the thump, the only way to remove it completly is buy or build a speaker protection relay, as for the voltage it could be just down to the broken pot, replace this part before you do anything else just to see if it is. thanks chris

31st March 2009, 01:06 PM	#8
jerryo diyAudio Member Join Date: Jun 2007	Hi planet10, have got it now so thanks again. Cheers dude. Hi reddish 75, there is some choice of trim-pot from Farnell; would a rating of 0.5w be OK? it does not give a figure on the parts list.

31st March 2009, 11:53 PM	#9
reddish75 diyAudio Member Join Date: Aug 2006	i use these you can bend the back legs to fit without extending then, so just the front one to do! http://uk.farnell.com/bourns/3329h-1...20k/dp/9354140

1st April 2009, 05:40 AM	#10
jerryo diyAudio Member Join Date: Jun 2007	Hi reddish75, those are the ones that I was looking at myself. I will do both of them (vr5,vr6) of course. The service manual from planet10 gives a different layout to the amp that I have and has another trim-pot (vr7) for setting the output display led`s. I need to have a close look to check whether the instructions given for setting the idle current still hold true by using R653,R654.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)