SB Radio died

One of my SB radios died, as in it wouldn't power up.

I suspected the wall-wart PSU, however when I tried the PSU from another (working) radio, no change. When I tried the PSU from the non-working radio with the working radio, this also does not work; I wonder if the failing radio has killed the PSU, or vice-versa. But I would have expected the PSU to be short-circuit / over-current protected; it's an original PSU, not a 3rd party replacement. I haven't yet tested the output of the PSU with a meter.

Even odder, I bought a battery for the non-working radio, and this would not charge in that radio, but when I tried that in the other (working) radio, it still wouldn't charge. And the (good) battery from the working radio would not run the non-working radio. Is it possible that the non-working radio killed the new battery? Otherwise, I coincidentally have been sent a duff battery.

I bought a 3rd-party replacement PSU, and that runs the working radio, but not the non-working radio. Trying the new PSU on the non-working radio did not kill it.

So, any ideas about what's going on? And, are there any particular components within the radio's power supply circuit which typically fail?

TIA