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I have a VFD (vacuum fluorescent display) unit from a piece of test equipment that has developed leakage between the anodes (plates). This leakage (~50 kΩ to ~250 kΩ) has been verified after physically removing the driver components which completely isolated the grid, heater and anodes. The only other leakage path would be the PCB as the VFD is still mounted on the PCB, however I have thoroughly cleaned (alcohol) the areas on the PCB where the display is mounted. The VFD has very low hours of use and the brightness (emission) is still strong. The symptoms of the anode leakage manifests itself as 'ghosting' segments.

What is the mechanism for this failure?

The vacuum appears OK as the getter indicates no problem. Is there a solution to remedy this issue or is the display ready for the trash?

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    \$\begingroup\$ Not my area of expertise, but I did find a post about ghosting being caused by a degrading power supply affecting bias levels here: eevblog.com/forum/repair/vfd-unwanted-segments-glowing \$\endgroup\$
    – vir
    Commented Oct 20, 2022 at 22:44
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    \$\begingroup\$ rfdes, It would help if you disclosed the VFD make and model; and schematic, if possible. I have a pulled VFD (I pulled it, myself) that was designed in 1985 by Industrial Electronic Engineers, Inc down in California, USA. I contacted them just a few months ago and spoke with a vice president there (she has been with the company since before 1985!) and she was VERY helpful. I got schematics, programming details, and everything else I could possibly want. She had to dig. But she put in the time. And for no money in exchange. She and the company are just nice folks. Have you tried any contact? \$\endgroup\$
    – jonk
    Commented Oct 20, 2022 at 23:06
  • \$\begingroup\$ Have you ruled out any other cause of leakage from the drivers? I'd more suspect there, or possibly even conductive no-clean flux. There isn't much of a way to leak inside the tube, unless contaminated or made of poor materials. Does it have a getter? If so, use an induction ring heater to re-flash it. \$\endgroup\$
    – rdtsc
    Commented Oct 21, 2022 at 12:00
  • \$\begingroup\$ I removed the drivers (UDN6118) from the PCB in an effort to isolate the display pins. Still noticed the anode to anode leakage. I then completely removed the VFD from the PCB, performed a thorough alcohol cleaning around the pins and the leakage persists. So the problem is internal to the display. The getter exists and based on its color the vacuum is still present. I would like to know more about 're-flashing' Please explain. \$\endgroup\$
    – rfdes
    Commented Oct 21, 2022 at 18:20
  • \$\begingroup\$ Googled articles such as this seem to say that re-heating the getting ring (and only the getter ring) for a few seconds causes it to emit more "getter" and thus sometimes improve vacuum. That article also says that baking the display at 500F/260C might also work, but I haven't tried it. \$\endgroup\$
    – rdtsc
    Commented Oct 21, 2022 at 19:29

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