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Autotransformer ID


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My guess...a T10A autoformer, which will reduce the voltage by 9dB. You would need to pass a low voltage sign wave across 0 and 5 and measure it.  The voltage across 2 and 5 should be equal to .3535 times the input voltage.  You would need a true RMS meter to measure the voltage.

 

Mike

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  • 2 weeks later...
On ‎7‎/‎24‎/‎2017 at 6:42 PM, djk said:

A cheap meter with LCR can measure the inductance, and then you can calculate the turns ratio.

 

https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=lcr+meter&_sop=15

Thank you djk, all we need now is a chart for all of the T?A autotransformer winding ratios  and how to translate the mH values when found

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This chart comes from Bob Crites web site...

 

http://www.critesspeakers.com/3636atz.pdf

 

As you can see, if you measure the inductance between taps 0-5, divide it by 2.833 (9db), you should get the inductance between taps 0-2.

 

If you have a good DCR meter, I believe you can accomplish the same thing.  I measured the DCR on a 3619 autoformer.  .37 ohms between taps 0-5.  .14 ohms between taps 0-2.  .37 / .14 = .2.64.  My meter only carries out to 2 decimal places, so this falls between 8 and 9 db attenuation.

 

Would you agree djk?

 

Mike

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  • 2 weeks later...
On ‎7‎/‎24‎/‎2017 at 6:42 PM, djk said:

A cheap meter with LCR can measure the inductance, and then you can calculate the turns ratio.

 

https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=lcr+meter&_sop=15

Thanks djk for the link, picked up a LCR for about $20. Sure it isn't as accurate as the $100+ meters but I think it will do the job.

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