Classic Hifi Care

Last week we had a big storm come though and we were without power for 3 days ... thankfully I had the old generac I purchased for Y2K saved the day ... the idle circuit was plugged so it would not run even... it sorta loped , and when I tried the astro-sonic the low hum this unit always had varied with the generator , telling me I have stray AC getting in somewhere... I even flipped the AC cord and made no difference ... this unit has been re capped completely including the radiohead ... the hum remains ... Do I need another cap from AC to ground ? maybe a cap to the center tap of the transformer? ... I am stumped as to where this AC is creeping in...as I stated when it gets turned on it sounds like a guitar amp with no input just a slight hum... once music starts it fades into the background ... and is not noticable...

The only suggestion I'd make is to bridge the filter caps with caps of the same value, known to be good. If that does not yield any usable information, you might try bridging the filter caps with ones with larger capacity and voltage ratings to see if those make any difference. There is always the possibility of having a bad new capacitor.

Unfortunately I have done that with no change in the hum...I figured it had to be in the radio/preamp chassis because if I unplug it from the power amp the hum goes away. I have plugged in a direct source to the power amp with no hum ... I have recapped the chassis without any change in the hum, I figure it has to be a bad ground somewhere ...but I still haven't found it...

Have you tried running a ground wire from the radio/preamp chassis go power amps?

Chris Campbell