Determining Output Transformer Primary Impedence

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4/16/2003 4:53 PM
Greg	Determining Output Transformer Primary Impedence I'm wondering how to do this. I have several lying around that were pulled from old Hammond organs and I can't get a reading that is in the range I expect to see.     Thanks   G

 

4/16/2003 5:28 PM

tommy

You have to inject an AC signal onto one winding and then measure AC voltage on all the other windings/taps. Then you back calculate using the turns ratio by squaring the turns ratio to get the impedance ratio.     So if you measured 1V on the output winding and it gave 25V on the primary winding, that's 25:1 turns ratio, squaring that gives a 625:1 impedance ratio. If you know that the output winding is 8 ohms, then 625*8=5000 ohm primary. If the output is 4 ohms, then 2500 ohm primary. You have to make some educated guesses to figure out exactly what it is. Knowing the application it was in beforehand gives you ranges to expect. A pair of 6L6's likes about 5000 ohms. A pair of EL84's likes about 8000 ohms. And so on....     Chris

 

4/18/2003 9:21 PM
Greg	Thanks for the info! Have a good weekend.     Greg

 

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