Greetings all ! I am new around here and in desperation on line I found your forum .I was given a Chinese-made 7 Star auto transformer which went down a few months ago. I opened same and found the sliding switch at the top damaged . I tested for continuity and am getting a reading with the two ends of the coil on the input side and that single end on the output. When I bridge the socket pockets of the switch I get no reading.The fuse is OK. Does anyone have a Schematic for this type of transformer or could someone shed some light on what I may be missing .Because of switch damage I am planning to run it straight 220/110 [step-down for which it was used] Thanks for any input and be Blessed.

 

Welcome to AAC.
Are you aware that an auto-transformer does not provide any isolation from the mains, so something driven by it will be 'live' and dangerous?

 

Welcome to AAC.
Are you aware that an auto-transformer does not provide any isolation from the mains, so something driven by it will be 'live' and dangerous?

Thanks for your concern Alec_t , Yes I am aware of the dangers of the single winding Auto transformer. Once again, thanks for your concern

 

I can't say at all whether or not schematics here: http://iseinc.com/staco/EngineeringDrawings/L501B.pdf might help you. I just pointed to one example.

It will be different based on what country your in.

It's VERY important to fuse the wiper. You CAN also fuse the input.

If you bought it for the VA rating at say 240, you can't usually get the same VA rating on the output. The current rating for step down would be the same as the 240 current for the 240 VA rating, making the VA rating at 120 V, 1/2 of the rated 240 VA rating.

This would not be the case with a normal 240:120 transformer. VA Pri = VA sec

With an auto-transformer, the current can't exceed the input rating. That's why the wiper is fused.