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Hoffman Amps Forum image Author Topic: Measuring output trasnformer secondaries  (Read 2274 times)

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Offline texwest

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Measuring output trasnformer secondaries
« on: April 01, 2021, 04:58:23 pm »
Hey guys, since Classictone went under I'm looking at different options.

I bought at Hammond deluxe reverb OT.  Whenever they come in a just test them to make sure nothing is wrong.  I can test from the blue to red and the brown to red and get about 200ohms on both, but if I measure from blue to brown I get an OL with a - sign.  I tried this with the classictone and I can get the ohms from blue to brown.  I also tried it with a heyboer and can measure from blue to brown.

Is this a problem?  Should I send it back before I even try loading it into an amp?

Thanks

Offline pdf64

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Re: Measuring output trasnformer secondaries
« Reply #1 on: April 01, 2021, 05:43:45 pm »
Autoranging meter?
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Offline texwest

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Re: Measuring output trasnformer secondaries
« Reply #2 on: April 01, 2021, 06:04:26 pm »
Yes it's auto ranging.  It's funny that it works on the classictone which measures nearly the same. Around 200ohm for each push-pull side.

Offline texwest

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Re: Measuring output trasnformer secondaries
« Reply #3 on: April 01, 2021, 06:11:37 pm »
Haha showing my ignorance here.  When I shifted to manual range it worked.  I've never had to move my meter over to manual ranging before.  If you care to enlighten me why it wouldn't work, I would be appreciative.

Offline pdf64

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Re: Measuring output trasnformer secondaries
« Reply #4 on: April 01, 2021, 06:14:22 pm »
It’s due to the inductive kick back, when the meter switches range.
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Offline texwest

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Re: Measuring output trasnformer secondaries
« Reply #5 on: April 01, 2021, 08:09:44 pm »
Thanks PDF!  You respond to so many of these threads.  I want to thank you for your extensive knowledge and sharing it.

Offline PRR

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Re: Measuring output trasnformer secondaries
« Reply #6 on: April 01, 2021, 10:39:39 pm »
Short the secondary to kill the inductance which is (as said) confusing the autorange.

I do think that 10 or 20 Henries is about the limit for these auto-meters, and the inductance at VERY low current (such as meter-test) is very different from working inductance at normal current, so it does not even hint at which iron may be "better".
« Last Edit: April 01, 2021, 10:41:53 pm by PRR »

 


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