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brucetassin 21st December 2010 10:29 PM

Output transformer
Would someone suggest a reliable way to test an output transformer.
I know I can use an ohm meter to verify shorts or opens but that does
not tell the whole story. I'm not asking how to determin impedance. Replacement is a good way I know, but I dont have a spare to do that.
If I could determine whether or not the OPT is good or bad I might save myself buying one I dont really need.

DF96 21st December 2010 11:06 PM

Measure primary inductance, with the secondary open and then short circuit. There should be a big difference between these two measurements. If not, it has a shorted turn somewhere.

Connect a 6.3V AC heater supply to the secondary, via a wirewound resistor (5-10 ohms, 5-10 watts). Measure the AC voltage across the secondary, and then the AC voltage across the primary (which is used as the 'secondary' in this test -i.e. we use it back to front). The first voltage should be somewhere around 3-6V, the second voltage should be 100-300V. The exact values depend on the transformer details. If they are much lower than this then it probably has shorted turns.

Yvesm 22nd December 2010 08:11 AM

Look at :

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