[Kenwood] TS-930 vacuum-fluorescent display problem

[Ken & Marlene]

My winter-time project TS-930 has a problem with the vacuum fluorescent display. Parts of some digits are noticeably dimmer than the rest.

 I've checked the voltages and waveforms against the schematic, and everything appears OK. The filament is getting 7Vp-p at about 20 KHz, the gate signals are swinging between -44V & +2V and the segment signals are swinging between -44V & +5V.

 Some scribe once suggested that vacuum fluorescent displays that haven't been used for long periods of time seem to lose their brightness ( does the phosphor get lazy? ) and can be rejuvenated by letting them run continuously for several days. I've tried that, with the frequency set to 28.888.88 but can't see much, if any, improvement.

 Any help or suggestions would be most welcome.


Ken, VE3FIT