Trevor Wilson wrote:

**You need to measure the power supply Voltages, to verify. If the
supplies are within spec, then the display may well be faulty. A VFD
(Vaccuum Fluorecent Display) is like a valve. It will wear out.

This is quite true but if it's had little use that's presumably not the reason.

VFDs are pretty long-lived. I still have one one a 1988 VCR hat's a little
'watery' now but still functional.

Graham