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Author Topic: Testing Mod iron  (Read 788 times)
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KB5MD
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« on: January 30, 2024, 11:13:37 PM »

Is there a way to test modulation transformers other than in a modulator?  I have several and would like to test them if possible.  I know you can check for continuity but are there other methods?
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WB6NVH
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« Reply #1 on: January 31, 2024, 01:56:36 AM »

Sure.

What did you want to test?  Insulation breakdown?  Impedances?  There are modern ways to test things but I like using my old General radio 1650 bridge and some resistors to measure impedance ratios and so on.

There are people on here who know better than I how to do all this and they should be able to help you. All I can say is that I have not killed myself yet doing this.
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Geoff Fors
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« Reply #2 on: January 31, 2024, 12:05:12 PM »

I first run a megger on the windings to see if it passes that test.

Then I run 120VAC thru it to a small load, like a lightbulb, of the same size Wattage as the iron is rated for. 

Let is sit for a day or so like that and see what you note for heat on the case, and maybe put a scope on the loaded secondary to see if there is any sinewave distortion.

If you aren't sure of the impedances, the bridge method is a great method. 

Otherwise, you can use an audio signal generator, some precision resistors, and a trustworthy voltmeter.

73DG
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K8DI
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« Reply #3 on: January 31, 2024, 12:12:27 PM »

One thing that will determine how to approach this is whether or not you have data on the transformer.  If you know its ratio and intended primary and secondary impedance, it’s easy to test if it indeed matches, or is partly shorted, etc.   It also gives some guidance as to voltage needs, therefore hipot test limits. You’d already know the power level and could use that and its impedance to figure voltage and current. As long as it isn’t partly shorted nor fails hipot, its good…

If it’s a random transformer, you can find the ratio and measure the inductance and then guess about what impedances it should match, then guess the power level, then guess the voltage and current, and conclude by saying you guess it’s good…..

So which group do you have that you want to test? ;-)
Ed
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AMLOVER
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« Reply #4 on: February 07, 2024, 12:17:37 PM »

https://www.bunkerofdoom.com/lit/modtest/index.html
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