In message , Jack Twilley
writes
I accidentally reversed the polarity of my DC power supply. I blew
the fuse in my TNC, but I can't find a fuse in my TR-7400A and the
only fuse I see in my TS-520 appears to be for the AC power supply.

What sort of damage could these radios have suffered?

You may have blown the 'idiot diode' as well as the fuse..

Mike
--
M.J.Powell