[NJARC] Power Supply Question

[njarc@mailman.qth.net]

Greetings Joe
Interesting radio problem.  Here are some other checks you can preform
until the calvary arrives.

Power transformer checks:
Warm or hot after 30 minutes?  Warm = OK, Hot = troubles.

Source of 120 cycle hum:
Ground wiper of volume control, does hum go away?
If yes then source of hum is before audio amplifier.
If not then source of hum is in audio amplifier.

In any event, substitute all vacuum tubes one at a time with tubes you
trust to eliminate heater to cathode leakage (tube checker short test is
helpful here).

Check B+ regulation.
Measure DC voltage on B+ line.
Set meter to AC volts to read ripple voltage.  Divide this reading by the
first and multiply by 100.  This should be % regulation.  As a guess,
less then 5% should be OK.  This is a crude approximation, John suggested
an o'scope which is preferred (if you have access to one).

Let us know what you find,
Jim
 
> At 10:04 PM 1/2/03 -0500, you wrote:
> >Hello and Happy New Year to all.
snip
> > The only problem I have with the radio is the constant 120 cycle hum.
> >Thanks in advance for your help.
> >Joe