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I have this old transformer and I would like to measure its output voltages.
(Attachment Link)
Its input is 220V mains (blue wires) and it has two outputs, 12.5V (brown wires) and 18V (red wires). I'd like to measure the actual voltages coming out of the brown and red pairs. This transformer is used to feed an old industrial motherboard.
I have a 110V->220V consumer transformer (I am in the US) with a three-prong socket for the 220V output. What would be the right way to proceed and what safety tips should I follow to make sure I don't win a trip to the heavens? Would it be safe to directly connect the two blue wires to phase and neutral (with solid connections) and measure the red & brown outputs with a multimeter?
Thanks,
Vince.
Firstly, you need to connect the primary of the transformer you wish to test to the output of your 220v transformer, making a really solid job of it, as below:-
Using a proper power cord, strip the end of it which wil go to the transformer under test.(TUT)
Using a screw type terminal block connect the Active ("phase") to one side of the primary of the TUT, & the Neutral to the other.(as your terminal block is probably 120 volt rated, don't use two adjacent teminals-- leave a space)
It would be nice if you could mount all this in a plastic box, but you probably haven't got one, so wrap the whole thing securely in good quality insulation tape.--- use plenty!
Get another terminal block & connect the secondaries to it--- this prevents the possiblity of you shorting a secondary out whilst farting around.
Place the whole thing on an insulating surface like dry wood, or plastic.
Plug the 220v plug into the "110-220" transformer
Plug that transformer into the 120volt outlet, & step back.
If, after several minutes, the transformer under test shows signs of distress, it is, similarly to Monty Python's parrot, an "ex-transformer"'
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If it looks OK, measure each secondary in turn.
Note:- The "no load" secondary voltages will read higher than the labelled voltage, which is determined at rated current.