Cursitor Doom wrote:

Decided to use the scope itself as the 'dummy load' by plugging the psu
back into it. It now takes 1m 25s for the power resistor to reach 50'C
whereas previously it was just under 15s., so an unmistakable
improvement.
Does anyone know what temp I should expect this resistor to run at, BTW?
I mean if they're good for 70'C I could leave it powered up longer and
see if it tops out before reaching that.
Lots of stuff in commercial gear runs at 70 C or even hotter. I don't like
to see parts running that hot. Especially in something that might get
buried in a shield housing deep in the bowels of some piece of gear like a
scope. But, 70C is not insanely hot for a power resistor. Of course, I
have NO IDEA how hot it is actually supposed to get.


So, does the scope actually run correctly? That would probably indicate the
transformer is fine, and maybe there is some load somewhere in the scope
that is excessive, maybe a bad electrolytic? I've got a B&K scope here that
blows a $13 power module after 15 minutes or so, and I've gotten tired of
fixing it. Since every time the module popped, the interval got shorter,
I'm strongly suspecting a bad electrolytic, but a quick visual inspection
does not show anything obvious. I've long since replaced it with a Tek
scope, so I'm just going to take it to the surplus shop.

Jon