[R-390] Another (perhaps) silly ballast question

[Roy Morgan]

At 02:11 PM 1/4/2006, Barry wrote:
>Many thanks to all the replies concerning ballasts and transformers.... my 
>thinking was if I could find a 120V/60V transformer ... would provide the 
>12.6VAC necessary for the oscillator tubes. ...better than a big old resistor


Barry,

I would expect any transformer run at below rated voltage to work just fine.

NOTE: a 400 cycle transformer rated at 120 volts can be run at 60/400 x 120 
volts, or around 24 volts.  Same for 400 cycle variacs, one of which is now 
for sale on the e-place.

BUT: If you got a 24 volt filament transformer and ran it as an auto 
transformer, it should work fine.  Leave the primary open, run the 24 volts 
into one end of the secondary and run the 12 volt filaments on the center 
tap.  The power needed is quite small, so the smallest 24 volt filament 
transformer you can find would work.

Another thought: find a TV picture tube brightener. These are auto 
transformers which boost the filament voltage of TV picture tubes to get a 
little more life out of them.  I assume that picture tubes ran on 6.3 volts 
(?), and so you might have to re-wind the thing with four times the number 
of turns total, but that likely would  work just fine, too. Rewinding might 
not be practical - I have never taken one of these things apart.

>I have a much better plan now, though.  I'm going to implement it and if it
>works as I think it will, I'll post the results here.

Oh?  Well TELL us what the plan is!

Roy



- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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