N Cook wrote:

400 watt RMS amp for use on 240 V mains.
Destructed due to metal dropping in and shorting the amp .

How did that happen ? The 'cabinet' is supposed to prevent such things, it's an
IEC safety requirement.


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.

Sounds like an incompetent manufacturer to me. 8 amps will provide a continuous
2kW almost ! Given typical fusing characteristics, consider that up to 4kW for
maybe 10 seconds.


Shorted power trannies, burnt low power trannies and even a piece of 3mm
trace from the main bridge rectifier burnt through

IEC 60065 failure very likely.


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 ?

Probably something like 3.15A but you may need to add a surge-gard type NTC in
the mains input.

What make / model was it ?

Graham