[Tubesforme]

Well plates then. Anyway, measure the current.

You vould start with measuring the voltage between the centertap and the end that you know will open. Compare with the other end voltage. The centertap is tied to the  Rect Neg. (B).

The voltages across the half-windings should be the same and be practically zero volts. Wait till you have that volume fluctuating and see if one of them changes. Use two DMMs.
Any significant positive voltage relative to centertap should be regarded as bad.

Once confirmed, or you can go straight to it, insert milluammeter between the suspect winding end and the grid. See if the positive (from grid being positive and winding neg) current exists. If yes, remove the tube, see if it stops.


Lasy: see what resistance is of the section 1-2 of the vitreous resistor 25. As long as you are at it, check the whole resistor, all sections.

I really blew this one! I made an assumption. I had replaced the interstage transformer twice and this one was the third. I thought that the same problem was happening again because the volume would drop and suddenly come back up. On the bench, the chassis would not act up so I covered it with a cardboard box after putting my VTVM on the grid of the output tube, that had been giving the problem before and the signal tracer on the input to the 1st audio tube. It finally acted up after two days. It turns out that the second 24, RF tube was the culprit, this time, not the transformer! Thanks for all the tips.