Heat sensor turned 140 amp off !

Posted by: Roy Donaldson on 13 May 2001

Hi there,

I've got a 72 / 140 / FlatCap and last night after
about 4 hours of playing at half volume, my 140 turned itself off. Touching the lid, it was very hot and would not go back on. I opened the box up and could feel the heat coming out of it, after about 30 seconds, I heard a click and it came back on again.

This is the first time this has happened to the amp before so I'm a bit unsure if this is normal or if I should be worried about this ???

Cheers,
Roy.

Posted on: 14 May 2001 by Andrew L. Weekes

Roy,

There's a thermally activated switch, bolted to the main chassis inside the amp, that senses the temperature, cutting the mains supply in the event of overheating.

It may be due to the things mentioned above, the only other check I'd do is to see what temperature the amp runs at when idle for a few hours.

If the output stage bias adjustment has drifted, the amp could run hot all the time, in which case a trip to Naim (or a dealer) is in order for it to be adjusted.

Andy.

Andrew L. Weekes
alweekes@audiophile.com

Posted on: 15 May 2001 by Markus

Whe I was using a 140 I had this happen multiple times. 12:00 on the volume dial may be running the amp fairly "full out" depending on the source and speaker load. Were you using vinyl or cd?

My guess is that it's nothing to worry about. Whenever it happened to me it was usually pretty well into an extended, pretty high volume listening session. Which sounds similar to what happened to you. But it is a good idea to turn the volume down while it's shut down--otherwise it can startle the hell out of people when it comes blasting back on at high volume