[NJARC] Power Supply Question

[John Dilks - K2TQN]

Hi Joe,

I think the transformer is OK, because the radio works.  Re check the 
filter capacitors to make sure you put the correct value in there (there 
may be more than one, check them all).  Make sure each one's not defective 
(substitute).  If you have access to an oscilloscope, you can look at the 
B+ line for hum on top of the DC.  Follow it to it's source.

Also look for a tube with a cathode-filament short.

Look for a capacitor you might have missed when replacing them - also wired 
in, incorrectly.

Good Luck, it's going great so far.
John Dilks

At 10:04 PM 1/2/03 -0500, you wrote:
>Hello and Happy New Year to all.
>
>        Thank you to everyone who helped me a few months ago with the Sparton
>Console Model 15 that I am working on.  Well, so far, I've recapped it,
>replaced the power resistor and have a working radio.  It has very impressive
>reception without an antenna and excellent with an antenna.
>        The only problem I have with the radio is the constant 120 cycle 
> hum.
>I've tried to localize the problem by trying another speaker and substituting
>capicators.  No change there.  So what I've narrowed it down to is the power
>transformer.  I'd like to know if someone can help me make the final
>diagnosis and if I do need a new transformer, which one to get.   Is it
>possible to get the original rewound?   Should I be checking it without tubes
>and powered?  With tubes and powered?  I'll bring the radio to the next
>meeting so it can be tested.
>        For a quick reference the transformer has outputs for 2.5, 300, and 5
>volts.  It has 5 taps on each side.
>
>Thanks in advance for your help.
>Joe
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