transformer primary shorted to secondary?

[ibvee]

Got here a tube output stage, with a nice transformer. It's an old unit, and it has 300V on the balanced outputs to ground. When measuring in circuit, there's only 160 Ohm to the center tap of the primary, which is connected to the 300V to supply the plates of the tubes. Can't disconnect the transformer from the circuit atm, because my soldering iron broke in half (hehe, it's an old one and the plastic had gone really bad), new one is coming in tomorrow, so will try to check it then.

However my question: it's supposed to be an isolation transformer, is it even possible that these things go bad in such a way that the primary is near to shorting to the secondary?

 

[JohnRoberts]

Sure if the wire insulation breaks down due to high temperature, or old age.

JR

 

[ibvee]

Thank you. First time I've seen this, so was wondering.

Doesn't happen very often I guess.

Tx!

 

[emrr]

I have only seen that happen in a few power transformers.  Never in an audio type.  More common in audio to find shorting within windings. 

 

[ibvee]

And indeed, only 167 Ohms from the secondaries to the primary center... That's unfortunate.

Who makes the best STA-Level output transformers?