[Boatanchors] Variac low?

[StephenTetorka at cs.com]

Hi Fred:

I had thought that I might be overloading it.
However, the only load on the vintage 5U4 power supply are the bleed resistors of 50,000 ohms @ 430 v is 9 ma. and my VTVM reading the B+.

This variac is vintage and new to me.
Don't know what wattage rating but it had powered a 2000 VDC power supply for 2 x 813.

All the more curious.

Steve

Fred Olsen <fwolsen at wi.rr.com> wrote:

>StephenTetorka at cs.com wrote:
>> Testing a low voltage power supply.
>> However, the AC in was only 90 VAC out from the Variac at max control.
>> Variac by itself 115 VAC at max control.
>
>First, it's just possible that you might be overloading the variable 
>autotransformer.  The idling current (you didn't say that the PS was 
>loaded) of a very large supply might exceed the current rating of a very 
>small 'Variac'.  Can you measure the current out of terminal 3 (usually)?
>
>Given that you have the 'Variac' wired correctly it would seem that you 
>have it wired for straight line rather than boost.  Fine.  But then the 
>question arises of why you only get 115 at no load.  It's very uncommon 
>to have that low a line (mains) voltage in the U.S. or Canada.  So where 
>are you and what is your measured line voltage?  What make/model is the 
>autotransformer and how is it wired?
>
>If all else is correct might the 'Variac' be defective?  Perhaps a 
>cracked core?
>
>Good luck, be safe,
>Fred
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