GE 578 crackling
 

Hi, all, I hope this is the right forum to post my question:

GE 578 clock radio. Some years ago it used to work well for a time, then it would begin to crackle and produce unintelligible audio. I replaced the tubes today (I have more free time on my hands lately) and that brought it back to life, but it is still after a time popping and giving me garbled audio. It sounds good and loud when it works, but then it again begins to make nose.

Could anyone give me a hunch where to begin troubleshooting? I have a photofact, but I'd rather not replace every component in the set if I could avoid it. Audio output transformer failure? Hard to tell from afar, I know, but I'd like to bring it back again. Clock still keeps perfect time.

Google the phrase "silver mica disease"

When I was a kid, my dad would hand me a small plastic flip open display box with two IF cans in it, and point me to an AA5 (dad hated PC work). I changed a lot of them.

"Make sure you don't mix the two up when you install them!"

"Okay dad"... :D


John

Garbled audio usually is caused by bad (leaky) capacitors in the audio stages.

jr

If there is any 60Hz buzz or him in the audio you should change the electrolytic capacitors too.

AA5s usually have less than $15 worth of paper and electrolytic caps in them and those caps are time bombs... Better to change them as a preventative maintenance.

Wiggle all the tubes to clean the contacts. But yeah, silver mica disease.

I have a 660 clock radio, I wonder how similar they are/ aren't.