John E. wrote:
It's shorted, burned on the side against the board, the side of the diode
that has part of the p/n printed (of course)...

Best I can make out is (reading around the diode:
ITT
4?
47

Physically it resembles a typical 1A black epoxy rectifier.

Would this be 1n4147? The "47" is clearly visible, and I think I can make out
a "4" in the first part of the poorly-legible digits. No telling how many
digits between the two "4"s.

Any possibilities other than 4147?

Not wishing to trach granny, but this would be my approach:

Reverse engineer parts of the associated circuitry until I am reasonably
confident of what sort of application it is being used for, eg lf
rectifier, hs switch, flywheel, etc. Or more importantly, if it is a
zener.. It is normally not to difficult to work out what the diode is
doing and what sort of currents, voltages and frequencies are happening
to it.

At that point, wire in an external diode with a much, much higher spec
than the original - and measure the actual running parameters. I keep a
few huge and very expensive semiconductors just for this.

Then match a diode to that requirement, by measuring what is actually
happening - with any luck the spec will match to something with a lot of
4s and the odd 7 in its product name.

Assumptions about what things may be tend to bite..

--
Sue