4 Jul
2006
4 Jul
'06
9:42 a.m.
> Turns out
it is the power transformer ([...]). It continued making
> popping noises well over a minute after I unplugged it, and for a
> few seconds I was even mentally making sure I knew where the
> nearest fire extinguisher was, since it gave the impression it
> might actually catch fire.
yikes! Sounds like the potting is boiling or
burning off... > Tomorrow,
I'm going to try turning it on (very briefly, with a
> current-limiter in series with the primary) to see if it's healthy
> enough to give me useful voltage measurements. [...]
First, I'd
disconnect the filter caps and meter them for shorts! Any semiconductor diodes? Might be one or two of
those shorted too.
No semiconductors at all as far as I've been able to find yet. While I
haven't yet put much effort into searching, there are at least three
rectifier tubes, so I see no reason to expect semiconductor diodes.
Might be you shoulda reformed those OLD caps before
powering up on
full AC, or replaced them.
Perhaps - though, as I say, shorted caps are low on my suspicion scale
at the moment. Or do caps that fail shorted do so with a low enough
resistance that they don't dissipate enough power to get warm? If so,
it coulda been one of the caps failing in service.
As for a replacement transformer, I'm actually considering using
multiple different transformers, one per function, instead of a single
core with lots of windings. I might be able to use stock transformers
that way.
But first, I'm going to poke through it enough to draw a schematic of
the power supply portions of the circuit.
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