Re: Damaged resistor - what happens?

If black, brown, black, gold was the original color code--well, it's a
pretty strange code for a resistor, starting with black. But
sub-10-ohm resistors should have a gold or silver third band, not
black, so maybe it didn't change all that much.

My suspicion is that it _might_ be a flameproof resistor as you say,
but it's quite likely that it's a metal-oxide resistor. The flameproof
ones tend to act like fuses (to keep not only themselves but things
around them from flaming!), but the metal-oxides have a long reputation
of being able to not only melt the solder but burn a hole clear through
the board before they give up as resistors. Most of the ones we use
have a pale blue case that gets somewhat paler if they've run very hot
for a while. I've done some experiments with them, dissipating up to
ten watts in a two watt resistor for long periods, and noting that yes,
they do change value some, but nothing like a metal or carbon film
would. They will survive a long time (hours at least) at five watts
with only a few percent value change. Yours could indeed have been
orange-orange-black-gold before they got so hot that the paint changed
color. I'm curious if you found a schematic or something else to tell
you what the design value really was.

Cheers,
Tom

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