Are paper and wax wound line transformers going the way of paper caps?
You may or may not know that the winding wire that was commonly used back in the days before polyester was "DCC".
This stands for "Double Cotton Covered".
Cotton. like paper. is hygroscopic.

I've had a recent experience with a NOS Rola part becoming hot and bothered and the EHT dropping after more that an hour's running.

I have a plan to address this:

1. Boil the transformer in turps to dissolve the wax. (this has to be done outdoors on the BBQ side burner with a fire extinguisher handy)
2. Soak the transformer for a few days in oil-based polyester lacquer. First soak in lacquer thinned to 50%
3. Second soak in unthinned lacquer. Possibly more than one soak to get a good insulating build-up.
4. Oven dry in between at 110 degrees C.

What do you think? Might this work?

Worth a try, but don't like your chances.
Once EHT has been established I guess weak sections have already arced over and are thus unrecoverable.
I have in the past rewound the overwind with success, but the rest was too complex a job.
JJ

I guess it depends on whether there has been serious mayhem or just overall lossy insulation in the windings.
I have at least two LOPTs here where that applies, they work perfectly again when allowed to cool down.

If the transformer is still functional when cold, and you DO eventually need to rewind it, you can calculate the number of turns on the primary and its taps by temporarily winding 10 turns of wire on, hitting it with 1 volt 15kHz from a sig gen and measuring voltage from the bottom to the top tap - it will be a linear relationship from which you can calculate the turn numbers.

As far as the EHT overwind is concerned, a tripler (early CTV type) gets the right EHT when driven from the hor OP anode (without a winding on the transformer). I've seen that work very well on a Philips transformer after the shorted turn EHT overwind was removed with the aid of a hacksaw. Only way with those, everything is moulded and glued together with epoxy.