john smith writes:
Then we smelled it. A sharp electrical smell that told us something was
burning and not quite right. Steve quickly turned off the misbehaving #2
radio. The smell got stronger, but there was no visible smoke. A moment
later, when the realization hit home that we might have a serious problem, I
keyed the mike to tell Atlanta Center that we smelled smoke, may have a
developing issue with our #2 radio, [snip]

Another case of the electronic device in the circuit path to protect the
circuit breaker from overload.

How true! :-)

Now, if there are any EEs present, perhaps they can explain
why aircraft radios tend to fail in this manner whereas
nothing much of anything else in the electronic world fails
in a manner to produce heat and smoke. Are avionics units
designed so close to the components' limits to cause this
failure mode? I can understand a transmitter going up in
smoke (while transmitting), but a receiver?