[Milsurplus] LV Supply...

[gl4d21a at juno.com]

Rick:

An alternative to the Variac is to use a SCR or Triac control in front of the transformer.  Find the schematic for a light dimmer or speed control and duplicate it using a pass device large enough for the input current to your transformer.  The downside to this approach is possible RFI (needs to be in a metal box with filters on the input and output) and some loss in efficiency of the transformer.  The advantages are it is cheap, small, and almost as good regulation as a variac.  And, if you are so inclined, a feedback loop will make the output very stable.  Power Designs used to use this approach in their lab power supplies.  

HTH
73,
George
W5VPQ


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