On 14 Juni, 03:25, "Phil Allison" wrote:
"powerampfreak"



I was given an oscilloscope, a Fluke PM3082 from a retired industrial
electronics engineer.
He said that during a measurement, the oscilloscope's powersupply just
bang and a flame came out of the rear panel. After this, the scope was
left for several years...until I got it.
The mains fuse has really exploded. Shattered glass in the fuse
holder. A brief examination of the primary side of the smps reveals no
shorts. The smps is an ordinary flyback supply. Mains rectifier ok,
switch ok, snubber, line filters all ok. Really don't know why the
mains fuse went.

** For a glass fuse to shatter and blow like that, there has to be an arc
from end to end - which would explain the flame out the back. For there to
be an arc inside the fuse, the AC current has to be very high ( *say 50
amps ) *which means there was a virtual dead short on the other side of the
fuse.

That short may have blown open during the event, typically a copper track
vaporises or a semi blows open.

It may also be that a EMI suppression cap across the AC supply ( or supply
to chassis) *shorted and then blew open.

Keep looking and checking things and you will spot something *- *like a pair
of wires poking out the PCB that connect to nothing.

.... *Phil

Great advice everyone! I'll continue investigating the powersupply
deeply!
I will let you know when I found out!