[Heathkit] SB-300/301 audio hum

[Joe Filice]

Mark,

My SB-301 developed this problem recently.  I tightened
all the screws holding the IF board (which also contains
the audio stage) to the chassis and the hum went away.
I guess it was a grounding problem.

Joe Filice KQ6GL

> 
> 
>   Wondering if anyone else that has a SB300 or 301 
> receiver has a very noticeable hum that can be heard
> in the speaker when the volume control is all the way
> down.
>  The level of the hum is not affected by the volume
> control at all, and it isn't heard when the unit is in the
> standby mode. I'm wondering if its due to the fact the
> audio tube is right next to the power transformer.
> 
> Mark  WB8JKR