NAD S300 int amp problem - 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 12th April 2007, 01:14 PM   #1
diyAudio Member
 
Join Date: Jun 2004
Location: Hants
Default NAD S300 int amp problem

I have a faulty NAD S300 int amp which goes into protection mode when it is switched on. The LED on the front panel is flashing.

I have found a few people who have reported the same problem with this amp. Can someone tell me what the problem is and how to fix it? Thanks.
  Reply With Quote
Old 13th April 2007, 02:24 AM   #2
Leolabs is offline Leolabs  Malaysia
diyAudio Member
 
Leolabs's Avatar
 
Join Date: Dec 2004
Location: Bukit Mertajam
Send a message via MSN to Leolabs
Do you have any electronic background???
  Reply With Quote
Old 13th April 2007, 02:32 AM   #3
diyAudio Member
 
FastEddy's Avatar
 
Join Date: Jun 2006
Location: North Californie
Don't throw it away ... but you should know your way around some test equipment to fix it right ... A flashing LED would most likely indicate that the output stages or power supply has problems.
  Reply With Quote
Old 13th April 2007, 06:50 AM   #4
diyAudio Member
 
Join Date: Jun 2004
Location: Hants
I do have electronic background. I have repaired a few transistor amps and built a gainclone.

The NAD S300 manual said the flashing LED means it is in protection mode. I know a few people had the same problem with their S300 amps and they were fixed by NAD for about 60 UK pounds. I am thinking of having a go at the repair myself before I send it to NAD.

Let me know if you have any more advice. Thanks
  Reply With Quote
Old 16th March 2009, 10:23 PM   #5
fjcbs is offline fjcbs  Portugal
diyAudio Member
 
Join Date: Mar 2009
Default NAD S300 problem

Hi hifienthusiast.
I have a NAD S300 wich began to have cracking noise on left channel with volume at any level (even in MUTE) and now it has the power led blinking fast.

Did you find the power supply problem?
Can you help?

I have basic electronics knowledge and have been poking inside with a multimeter and found some diferent voltages in a small transistor on each channel... also the amp module for the left channel shows some 40+ voltages on some points and the right channel is at 0.

Thanks.
  Reply With Quote
Old 17th March 2009, 01:10 AM   #6
dtm1962 is online now dtm1962  Canada
diyAudio Member
 
Join Date: Apr 2003
Location: Sarnia, Ontario, Canada
Default S300 Repair

I have had the fast blinking lights which indicate that it in protection mode as a result of irregular voltages as a result of a component failure or bad solder joint.

Chances are the ZTX653/753 transistors have overheated and are leaking or a solder joint from top of board to bottom has separated. I resoldered all solder connections in the area of the discoloured circuit board surrounding these transistors and voila it worked again.
I have done the NAD recommended reliability modification via changing out the 4 resistors that allow these transistors to run cooler and more reliable.
These transistors are located on the main board and are the transistors that are grouped together with 8 small TO-92's together for each channel. You will notice the circuit board in this area has discoloured as a result of the excess heat. I have successfully repaired it without changing out the transistors so I conclude that the solder connection went bad as a result of the excess heat. Email me dmullins@cogeco.ca if you need more assitance.

Thanks,
__________________
Dan
  Reply With Quote
Old 17th March 2009, 01:15 AM   #7
dtm1962 is online now dtm1962  Canada
diyAudio Member
 
Join Date: Apr 2003
Location: Sarnia, Ontario, Canada
Default fjcbs : Re Repair

The channel that measures 40+ volts is the channel at fault as I had the exactly the same problem.... Try resoldering around the transistor where you measured the voltage, then try soldering throughout this area, and finally the transistor replacement.

DO the reliability mod to make it run cooler.... I even added heatsinks on the transistors to draw the heat away from the transistors and circuit board...

Email me for details.. dmullins@cogeco.ca
__________________
Dan
  Reply With Quote
Old 17th March 2009, 09:32 AM   #8
fjcbs is offline fjcbs  Portugal
diyAudio Member
 
Join Date: Mar 2009
Thanks dtm1962.

I will try the solder repair first, sometime this week.

Also, aparatusonitus provided me with the service manual and now I can find my way a lot easier.
  Reply With Quote
Old 17th March 2009, 09:48 PM   #9
fjcbs is offline fjcbs  Portugal
diyAudio Member
 
Join Date: Mar 2009
thanks again dtm1962.

today after work I got home and redid the solder point where you said and my beloved S300 works again!!!

I will try to get some resistors to do the reliability mod and also some heatsinks as you mentioned.

The funny think is that last saturday I went to buy some Kimber 4TC cable to bicable my JMLab speakers with the current 8TC cable I had and as soon as I got home to set the cables connected the amp died! I don't think it was the new cable because the left channel was already making some unordinary noise...

Well, listening to the repaired amp, it sounds much more alive and "fast". Don't know if it is because of the repair job, the new cable or just placebo for me being capable to repair the darn thing all by myself!
  Reply With Quote
Old 18th March 2009, 05:10 AM   #10
dtm1962 is online now dtm1962  Canada
diyAudio Member
 
Join Date: Apr 2003
Location: Sarnia, Ontario, Canada
Default Good to hear you have fixed it!

Your welcome..... as it is great that we can help each other continue enjoying our beloved hobby!

I bought replacement transistors just in case but .... if it aint broke don't fix it!

Keep an eye on it but I would definitely changed out the resistors (as part of the mod) and add heatsinks for peace of mind!
__________________
Dan
  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
NAD s300 HFERRAO Parts 0 11th May 2009 12:44 AM
Nad S300 DFroehlich Swap Meet 1 7th April 2008 04:51 AM
Best bias for 400a/S300? centaurus3200 Pass Labs 2 21st April 2007 12:12 AM
Theshold S300 Amp Gwiesner Parts 0 17th November 2006 07:51 PM
opinions on S300 subwoofer from loudspeaker kit diy_newbster Subwoofers 0 30th April 2003 12:42 PM


New To Site? Need Help?

All times are GMT. The time now is 04:27 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