NAD 3020 hum - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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
Reply
 
Thread Tools Search this Thread
Old 30th May 2004, 04:36 PM   #1
rigadig is offline rigadig  United Kingdom
diyAudio Member
 
Join Date: May 2004
Location: Lincolnshire or Newcastle
Default NAD 3020 hum

Hi, I have an old 3020, it worked fine, then one day, it just started making a low humming sound through the speakers. It started quiet, but increased in volume over time untill it go quite loud, the stayed at this level. If i turned the amp off for a couple of seconds, then back on again, the noise dissapeared for a minute or two, then started again (increasing in volume as before). I know a little about basic electronics (but not much in depth transistor theory or power electronics), and have no idea what is causing this, because one day the amp was fine, and the next this strange problem.

An electrical engineering proffessor at my university (Newcastle) told me that he thought it could be the regulator (but he was not sure because he never saw the amp) and told me to check using an oscilloscope (which i don't have!!). I opened the amp up, but I have no idea what a regulator looks like. I had taken the amp to a shop to get it fixed, but they charged me 25 to look, and said they could not fix it. When I opened it there is a very thick layer of brown dust over the whole board (could this be causing the problem), so i don't think that the shop ever really tried to fix it.

Basically, if anyone can help I would be very greatful because i don't want to throw it away.
thanks
  Reply With Quote
Old 31st May 2004, 01:53 PM   #2
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
It sounds like the big electrolytic power supply capacitors may have got a bit old and dried out. They should be relatively easy to replace. Have a look for two big cylindrical objects connected near the transformer, and tell us what it says on them.

As for the dust, a good clean out wouldn't hurt!
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 31st May 2004, 02:59 PM   #3
rigadig is offline rigadig  United Kingdom
diyAudio Member
 
Join Date: May 2004
Location: Lincolnshire or Newcastle
I am away at the moment, so I will have to wait until tuesday evening to check what they say on them. I will buy a can of CO2 as well to blow some dust off. Is replacing them just a case of unsoldiering them and replacing them with any capacitor from an electronics catalogue of the same capacitance value?
Do all capacitors die of old age like this, or just the big power ones?
Thanks
  Reply With Quote
Old 31st May 2004, 03:26 PM   #4
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Yes, the caps need to have the same capacitance value and working voltages. Make sure when replacing them that you connect them up with the correct polarity, or they will go bang and make a real mess. Oh, and being roughly the same size helps as well!

Electros do tend to give up after a while, due to evaporation out past the seals. If you really wanted to go for it, and have the spare cash, then it wouldn't hurt to replace all the electrolytics in the amp, (but watch out for non polarised versions)

As for cleaning, a hoover with a soft furnishing attachment works well, and switch cleaner for all the pots, switches, and connectors you can get to.

Compressed air in cans is way too expensive for something as robust as an amp, save it for CD mechanisms and cameras.
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 31st May 2004, 03:36 PM   #5
Geoff is offline Geoff  United Kingdom
diyAudio Member
 
Join Date: Apr 2001
Location: UK
Please bear in mind that the NAD2030 has separate supplies for the pre-amp section and the power amp (the schematic can be found on my website) and it would be wise to change both sets of capacitors unless you can determine which are causing the problem (if indeed it is a capacitor problem rather than something else).

The reservoir capacitors for the pre-amp section (C905, C906) are 470uF 35V and those for the power amp (C901, C902, C915, C916) are 2200uF 35V.
  Reply With Quote
Old 31st May 2004, 03:48 PM   #6
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Thanks Geoff.

BTW, did you know your site is down at the moment? I went there earlier to see if you had a schematic for the NAD, and couldn't get in, and ditto just now...
__________________
Rick: Oh Cliff / Sometimes it must be difficult not to feel as if / You really are a cliff / when fascists keep trying to push you over it! / Are they the lemmings / Or are you, Cliff? / Or are you Cliff?
  Reply With Quote
Old 31st May 2004, 04:11 PM   #7
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
I see that the amp has the ability to seperate the preamp and power amp stages via what looks like a jumper cable. If there is a set of terminals marked "Pre Out" and "Power In" on the back that are coupled together you may want to try disconnecting them and connecting eg a CD player directly to the Power In terminals.

This will allow you to determine if the hum is coming from the power amp or preamp stage. It is most likely though to be the power amp stage, as other posters have said the electrolyte in the power supply capacitors will have dried up and they will need replacing. As long as they are the same dimensions, the same or greater voltage, and the same or greater capacitance they will work well. It may be worth using 105oC rated capacitors if you can as these will last longer.
  Reply With Quote
Old 31st May 2004, 04:50 PM   #8
Geoff is offline Geoff  United Kingdom
diyAudio Member
 
Join Date: Apr 2001
Location: UK
Quote:
Originally posted by pinkmouse
Thanks Geoff.

BTW, did you know your site is down at the moment? I went there earlier to see if you had a schematic for the NAD, and couldn't get in, and ditto just now...
It's a Bank Holiday, what did you expect!

Seriously though, I seldom visit my own site (for obvious reasons) but there was no problem when I tried a few minutes ago. You perhaps tried during a busy period. One of the disadvantages of the 'free' webspace is that there is a limit of 1500 people at any one time accessing all of the BTInternet personal websites.
  Reply With Quote
Old 31st May 2004, 05:01 PM   #9
rigadig is offline rigadig  United Kingdom
diyAudio Member
 
Join Date: May 2004
Location: Lincolnshire or Newcastle
will it matter what type of capacitors i use then. Could I use for example some type other than electrolytic, film capacitors perhaps?, would these last longer? also, what is a 105oC? Can anyone suggest a good uk supplier of these components, so far i only know of maplin or RS
Thanks
  Reply With Quote
Old 31st May 2004, 05:50 PM   #10
Geoff is offline Geoff  United Kingdom
diyAudio Member
 
Join Date: Apr 2001
Location: UK
For the values in question, you will need to use electrolytics. 105degC is the temperature at which the design life span is determined. Other electrolytics will have a temperature rating of 85degC. The 105degC types will generally last longer, though this can vary from one manufacturer to another.

Forget Maplin (poor stock range) and RS (expensive). Try instead:

Rapid: http://www.rapidelectronics.co.uk/

or

CPC: http://custom1.farnell.com/cpc/default.asp

email me if you need some more specific advice.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Another NAD 3020 jerryo Solid State 17 3rd May 2012 06:39 PM
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 problems Neopsp Solid State 2 17th May 2002 02:34 AM


New To Site? Need Help?

All times are GMT. The time now is 12:05 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2