Output transformer

brucetassin · 21st December 2010, 09:29 PM

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.
Thanks....

DF96 · 21st December 2010, 10:06 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, 07:11 AM

Look at :
advice please, a setup to characterise opts

21st December 2010, 09:29 PM	#1
brucetassin diyAudio Member Join Date: Dec 2005 Location: Loganville, GA	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. Thanks....

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21st December 2010, 10:06 PM	#2
DF96 diyAudio Member Join Date: May 2007	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.

22nd December 2010, 07:11 AM	#3
Yvesm diyAudio Member Join Date: Jul 2004 Location: Ardeche	Look at : advice please, a setup to characterise opts