This problem just popped up.. everything has been great with the radio up till now. This is in my 1987 Chevy K5 Blazer..

All of a sudden, the amp is losing power, but only when the engine is running, it cuts in and out pretty badly, even at low volume. (no subs or anything, just 6x9's)

If I turn off the engine, and have the key in either the Acc or on position, the radio is able to play fine.

i did smell some slight "burnt electronics" smell for a minute, but it was very slight.

I'm normally pretty good at figuring out electrical stuff, but this one came out of nowhere, and I'm not sure where to look!

ps I tested the battery and alternator for voltage, 12.8V engine off, 14.1V engine on.