[Amps] 120 cycle hum from Henry 2K-4

[Ron Youvan]

> The Henry has full-wave bridge rectifier then uses an 8 Henry (700ma)
> filter choke with an oil filled .1mf (7500v) in parallel then an oil
> filled 20mf (5000v) cap to ground.

> I've been told those oil filled caps rarely go bad and usually last
> longer than we do.  Any clues where I should be looking to solve this
> hum problem?  Of course it's not really noticeable on SSB but I'm sure
> it's in there as well.

   The 8 Henry filter choke with an oil filled .1mFd in parallel then an oil filled 20mFd cap to 
ground is a tuned filter, tuned to 120 Hz.  If you truly have 60 Hz hum, you have a diode open in 
one of the arms of the bridge rectifier.    If you truly have 120 Hz hum, you have a "detuned 
filter" possibly the oil filled 20mFd cap has changed value.  Check the values of both caps first.
   With this, like all power supplies the HUM sounds greater with a higher current draw, from the 
supply.
-- 
    Ron  KA4INM - He who attacks the fundamentals of the American broadcasting industry
                  attacks democracy itself.        -- William S. Paley, chairman of CBS