Meat Plow wrote in message
...
On Sat, 14 Jul 2007 17:32:33 +0100, N Cook wrote:

400 watt RMS amp for use on 240 V mains.
Destructed due to metal dropping in and shorting the amp .
The only fuse is on the mains rated at 8 amp, maker's design rating,
which
shows no sag , discolour or anything like that, ie untouched.
Shorted power trannies, burnt low power trannies and even a piece of 3mm
trace from the main bridge rectifier burnt through and that had 2 runs
of
added solder over the track for current carrying, the other polarity
trace
overheated but not ruptured
I'm thinking of bridging that gap with a fuse and another on the other
rail
after cutting it.
The mains transformer is rated at 2x 47V,5 amp.
So drop the 8A fuse (for 2 KWatt !) to what value ? and the 2 added
fuses of
what rating ?

So what you are saying is that this catastrophic failure of a 400 watt amp
didn't blow an 8 amp fuse? I find that really hard to believe not that you
are making this up mind you.


Well semi-catastrophic, the positive side in a sorry state but the negative
rail side cold-tests ok so far. I was wrong when I said about the overheated
trace it was the ground return not the negative rail, the + trace burned
through as a "fuse", no deliberate necking at those points.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/