Hi mkstevo,I would say that this is normal. Having spent many years repairing video recorders which often used this type of display, being able to see a faint orange glow (often only visible in near darkness, as you describe) from the heaters was a good sign! .....
If that does not help, it could be inter-electrode leakage in the actual VFD itself.
Thanks for the input.
My VFDs are much smaller than nick's , and the heaters don't glow, but I'm happy that you can confirm that the glow is normal for bigger ones.
Nick has already tried replacing the electrolytics.
I don't understand how inter-electrode leakage could occur inside the glass, can you explain ?.
If you look at the pictures in post #1 you can see the graduated ghosting.
My suspicion was either too high HT, thus causing grid punch-through, or too high heater current causing an electron cloud to form.
Another fault might be the zener, mentioned in section 6.2 of this useful webpage : http://www.noritake-elec.com/vfd_operation.html
Whatever it is, I don't think it's going to take much to fix.