[PaulR]

That is interesting regarding the hum. This always had dripped wax visible under the transformer but the later one does not. I wonder whether they beefed up the transformer for later models.

Does the 137 have the same back corners as the later 135?

My working 135 has a hum which starts as soon as the rectifier warms up. I had something similar with my 365 and I cured it by adding an external smoothing choke instead of using the speaker field winding. Maybe the hum bucking coil doesn't work as well as it could. With large value capacitors available now I think we are a lot less tolerant regarding hum. I notice that I had put a 16uF smoothing capacitor in place of the original 8uF in the now not working one. The reservoir is still 8uf. I wonder whether this also hummed. I cannot really remember.

I asked Ed Dinning ages ago about rewinding the transformer but never pursued it as I had nowhere to put the set and had recently been given the 365. I am still pondering what to do about it!