Responses are coming thick and fast.
OK just been out in the garage with the power supply and I am smiling for now.
The heater does glow as I would expect, no signs of smoke etc, so perhaps it is just a scratch, but something I need to protect some how.
The mark in more detail
Glow
Glow
The small magnet is with the set, but not on the neck it is loose hanging down in the first image.
I wonder if anyone has a service manual for the set, possibly something with resistance readings for the LOPT, I could always try to measure it in situ.
Christopher perhaps I should have taken you up on the Pye VT4 when I picked up the Solartron scope?
Adrian