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wrankin 16th August 2011 01:58 PM

NAD 3020 Rebuild - thermal breaker replacement/source?
Hey Gang!

I have an old (first generation) NAD 3020 that I am rebuilding to serve as a front end for my music system. On one of the output channels the "thermal protection" device burned out and needs to be replaced. One of the previous owners had done quite a hack job in "fixing" it by soldering a lump of wire over the top of the device and I'm still cleaning up the damage. >:-(

On the first gen units this device (TP1, TP2 on the schematics) looks like it is a fuse. From reading around it appears that on later models they replaced this with a "bimetal breaker" (I am guessing that too many units were coming back for warranty repair due to a simple blown fuse).

So I need to replace the device but can't find the specs on the part. I figure that the fuse value is around 2 amps slow-blow (or possibly ~4 amps fast-blow?). Since I'm replacing this piece anyway, would it be better to put in the thermal breaker instead and does anyone have a pointer to a source for these?

Also one of the preamp channels is out, so if anyone has sugestions about where to look it would be most appreciated. :-)



Ian Finch 16th August 2011 04:54 PM

This part was real common and still sells described as an "Auto reset PCB mount circuit breaker" and they typically break after 1 hour at their rated current. So don't think they are exactly fast blowing! They should break within 1 minute at 200% however.
About $3 at any of the major parts suppliers.

wrankin 16th August 2011 06:36 PM

Thanks, Ian. That gives me a good place to start. A quick google shows several types available. I'll just bypass as a temp fix until I order. :-)

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