14 years later, now it's happening to mine. No battery, just the power adapter, 5A fuse.
Radio will randomly squeal then shut off. Sometimes will restart itself, sometimes not, then it will go for a while or quite a while before doing it again.
My spare A6 with battery does it also when battery is depleted, so I believe it's a low-no voltage problem. If I unplug the power from the first one in flight, no squeal, instant off.
Will have to test the volts coming from the power adapter I guess.
Stupid 9volt radios........ Had a DELCOM (12v) originally, great radio, til it wasn't.