On Mon, 2007-08-06 at 21:24 -0500, Stuart Rohre wrote:
> Reversal of DC polarity may have failed some electrolytic capacitors. Also,
> if it is working weakly, maybe a diode in a bridge rectifier is open. How
> long was the polarity reversed? That may tell if any active devices bit the
My experiences with reversed polarity is that the fuses are reliable
indicators of fried semiconductors. That semiconductors fail faster than
fuses open, so time isn't much of a factor.
ICs dislike reversed polarity and often short. Some ICs running off
internally (to the radio) regulated voltages may be protected by the
regulators, some regulators may feed full supply under reversed polarity
conditions. Small bipolar transistors base-emitter junctions often
(especially RF types) have lower break down voltages than the inverted
supply and the avalanche can do serious junction damage.
Expect to test and maybe have to replace every IC and every transistor
along with many electrolytic capacitors. And the miniature electrolytics
may have been poor anyway just from age.
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
TenTec mailing list