NAD C 300 AMP + Smoke

 

New member
Username: Designerpaul

Post Number: 1
Registered: May-10
Hello all, first up I have to say I know very little about audio equipment so please go easy on me!

I have recently been given an amp (NAD C 300) and some (what I'm told are) nice speakers, that had both been working but kept in a loft for maybe 4 years. The plan was to run the audio from my computer through the amp.

I connected the computer (Intel 2 Core Duo iMac) to the AUX input of the amp from its "Headphone Out" socket. I was careful to turn the volume right down on the computer before slowly going to about 50%. All worked great and sounded superb for about 30mins. I turned the volume down on the amp walked away, came back about an hour later and the amp seemed to have turned itself off. On trying the power button the LED next to the power button flashed red but then died. I tried once more and a whisp of smoke came from the amp and died completely, no LED.

So my questions are. Is this my fault? Someone now tells me that I should only use a lineout to connect to the amp as the headphone output will be too strong? I don't think my Mac has a lineout however? What should I have done?

Also is there anything I can do to diagnose the problem? I'd preferably like to have some kind of idea before I take it to repair. Are these things cheap to repair and is it even worth it?

Any help would be much appreciated, sorry for all the novice questions!..
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 14853
Registered: May-04
.

Stored electronic components age faster that those in use. You probably damaged the power supply of the amplifier. Smoke typically means you've increased the cost of repairs by a magnitude in coherence with the amount of smoke released and how loud you shouted when you first smelled the smoke (and sometimes how far back you jumped when the amplifier blew up while releasing the smoke). So, it's a compound equation and there is no set answer for your question regarding cost. I doubt this will be "cheap" to repair when you can buy another receiver for less than $100. If you want to get an estimate of cost, any repair shop will charge a minimal amount for that service.


.
 

Gold Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 3868
Registered: Feb-07
I had a NAD amp repaired a few years back for about 100 bucks. I never had any smoke emit from it, so Jan's formula here relating repair cost as a function of amount of smoke released would most definitely apply.
 

Platinum Member
Username: Nuck

Post Number: 14969
Registered: Dec-04
I always love the smoke/cost analogy.

Cacitors are painted to keep the smoke in.
 

New member
Username: Designerpaul

Post Number: 2
Registered: May-10
The wisp of smoke was relatively small and I remained relatively calm so maybe i have a chance?!

Opening up the amp, I can see a burnt mark around a small capacitor (marked "c 718"):

http://dl.dropbox.com/u/3454522/NAD1.jpg
http://dl.dropbox.com/u/3454522/NAD2.jpg
 

Gold Member
Username: Dmitchell

Ottawa, Ontario Canada

Post Number: 3869
Registered: Feb-07
That doesn't look so bad actually.

Don't forget those big caps can give you a nasty jolt, even when the amp in unplugged.
 

Gold Member
Username: Magfan

USA

Post Number: 1148
Registered: Oct-07
If the cap didn't take something really pricy with it when it popped, you might consider replacing all of 'em.
The amp should than be good for another decade.
 

Silver Member
Username: Hawkbilly

Nova Scotia Canada

Post Number: 915
Registered: Jul-07
First rule of electronics, that I was given. Keep the smoke in.
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