How to bench test an unknown vintage tube high voltage power transformer

Have you wondered how to test those unidentified power transformers you have laying around? See if possibly they would be useable for your application. Well, here is a method that I have followed for years. With the increasing costs of new transformers, it is well worth your time to see if they can be used. I have noticed lately that people are building less, due to cost. So, its time to think outside of the box, keep the hobby alive!

[curtisprice]

My Dad has a few dozen transformers of all sizes....big and small, tube, etc. in his electric shop. He was head engineer of power systems at Union Carbide. I will inherit a ton of electrical "everything". He is 86 years old, and sadly Alzheimer's has reared it's ugly head. It started a couple years back, and now that I have time to be with him...basically communication is over. Love your family because time flies! Great YouTube channel! ❤

[JurassicJenkins]

After all these years of ignorance, I’ve been transformed. Thanks for the video, well done! 😊

[elinbenson]

I use a door bell transformer to give me a 16V AC low current source. Once you find the output voltage with 16V input, you can calculate the turn ratio of the transformer, and calculate what voltage it will have at line voltage

[danrussell]

Iron is often the most expensive part of an amp. Thanks for a video that can help keep costs down and give new life to these old parts.

[douglasstewart]

Excellent presentation - As an old Tech. School teacher you are the best. Thanks

[keithschreiter]

Terry, Before I put 120 VAC into the Transformer I put A Signal Gerearter at 60 Hz at about 5 to 10 VAC into thr primary and measure the output leads and then take 10 volts and divide that into 120 volts. Then you have the ratio. then multiply the other output windings and come up with the output voltage on those wires it Lower the potenional high voltage before I put 120 volts into it and continue testing then you know what you are dealing with.
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[zulumax]

This is great information that benefits everyone in the electronics community. Please liberally share the old school tribal knowledge of the old radio folks! Even if one knows such things it is good to hear it repeated. Great job Terry! Please share more of these bits of treasured knowledge,

[Marwatt]

great video... please make one for the output transformer too

[bobblum]

Thanks, Terry!

Years back I knew someone who made up a board with a set of screw-terminal barrier strips, physically spaced far enough apart for electrical isolation. They then did the same basic tests Terry demonstrated, with the wires from each group of windings securely held in place.
They worked with a fair number of transformers, so making a test jig like that made sense.

[ross]

May I impress the advantages of putting all the secondary leads into mains style terminals. An enormous one is the inability of completing the circuit of an HT winding with your hands or fingers. Accidents can happen to the best of us.

[dhpbear]

One more rigorous test would be to verify that no windings are shorted to each other. :)

[ryanearnhardt]

Thank you! I have a old 20 lbs x former from an organ and didn’t know how to test it.

[joeteejoetee]

Love this video because: safety first!
What a treat to find a transformer with a 5 V winding too!

[edwardhannigan]

Great video Terry, very informative..Now I just need to find one of those transformers in my basement..! Ed..uk.😀

[vintagetubeamplifiers]

Another excellent lesson, thank you Terry. Now I feel confident measuring the replacement transformer from a Mercury 1000 for my Mercury 2000 tube tester that has 22 taps.

[amberyooper]

I usually use an isolation transformer to plug the AC into when I test transformers, but I realize that not that many people have one of those either.

[veritasconc.]

Nice shirt!
Thank you for your always easy-to-understand lectures!

[Easton]

This was the 4th video I watched on transformers and the ONLY one that actually explained the real-world application. All the others focused on the technical aspects of stepping up and down. WELL DONE!

[tomvarley]

one problem with testing a valve power transformer with a digital multimeter is that the back emf created when you disconnect the meter clips is so large that it can lock up the electronics of the meter. I had discovered this whilst testing a Leak stereo 60 - it froze the electronics in my Fluke 87 for quite a few seconds and it looked like the primary was O/C. I now only use my AVO MK V for testing inductive circuits.

[RA-Arg]

This kind of bench is the reason I am suscribed to this channel!!
Incredible lesson! cheers