Thanks for all the replies. What made me decide to replace the
transformer was that I just didn't think the initial repair would hold,
it was rather delicate to do. I had resoldered the tiny copper strand
back on the solder tab, I think the strand still had some
lacquer/glue/adhesive on it after attempting to clean it, and had less
than a millimeter of play; I just wasn't satisfied I had enough contact
surface and it was difficult to properly and cleanly wet the joint.
Ugh.

I ended up installing the replacement transformer, a 36v CT 1A unit
riveted outboard on the chassis, the original being 38v CT 500mA, and
cleanly tiewrapped the cabling to an existing harness and onto the PCB.

I measured the same voltages on the various screw terminals as with the
previous (flaky) transformer.

The fuse hasn't blown yet, and I have a fire extinguisher handy :-)

Thanks to all,