Low resistance in power transformer secondary

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Studiogearlover

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Joined
Mar 14, 2017
Messages
176
Hello DIYers!

A quick advise needed please.. i have an old tube amp as my next project. Starting with my power transformer.

Secondary should measure 300Ohms and 330 Ohms to ground according to the schematic drawings but I am not nearly there.. i am getting 200 Ohms and 220Ohms..

This means that this transformer going downhill?  Approx 50-60 years old transformer..?

Many thanks for the advise. !
 

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Studiogearlover said:
Hello DIYers!

A quick advise needed please.. i have an old tube amp as my next project. Starting with my power transformer.

Secondary should measure 300Ohms and 330 Ohms to ground according to the schematic drawings but I am not nearly there.. i am getting 200 Ohms and 220Ohms..

This means that this transformer going downhill?  Approx 50-60 years old transformer..?

Many thanks for the advise. !
I wouldn't expect a graceful drop in resistance over years. A possible failure mode is an insulation breakdown that causes nearby turns to short with each other. I would not expect a 33% drop in resistance from that failure vector.

Can you test the transformer functionally?

JR
 
JohnRoberts said:
I wouldn't expect a graceful drop in resistance over years. A possible failure mode is an insulation breakdown that causes nearby turns to short with each other. I would not expect a 33% drop in resistance from that failure vector.

Can you test the transformer functionally?

JR

Hey JR

Thanks for the note. I would need to wait a couple of days until I can fire it up... there is a special 2 prong cable I would need and I don't have it  yet.

I went through this  very nice little amp (attached) and besides the wax foil capacitors, everything else are pretty much within 15% +/- specs...

 

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If they had another vendor wind transformers it could account for it.  I expect it’s fine. 
 
Thanks guys for the suggestions. Will go through and check the other components and turn it on in order to see /check the voltages...  :)
 

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