VFD burnout?
 

The discussion of Adam's early GE digital clock radio got me thinking about one of my clock radios that has a vacuum fluorescent display (VFD). It's a Panasonic with a mirrored face, mid-80s. The clock digits are all becoming very dim. On the low brightness setting it is pretty much impossible to read, on the high brightness setting it is visible in low light. However, the radio dial (which I believe is part of the VFD) and the small indicator that lights when you set the time are still bright. Are the phosphors wearing out on the VFD or is there an electrical problem? It does appear that the segments that get the most use are the dimmest. Should I check voltages and if so, what are typical voltages I would expect to see on the various display pins? Is it possible to rejuvenate these displays?
Thanks!

I work on pinball machines, and the Gottleib machines loved using their VFD displays for scores.

Dimming is a problem on many of these. There is a simple trick we'd do. We find the heater connections on the displays and connect them to a DC voltage a bit higher than normal, for just a two seconds. You want the filaments to get a similar color to a tube filament.

This usually helps to greatly brighten the unit up. However...we get similar rejuvination letting them run for a couple hours. If its a clock radio, its already running all the time..so you may need to check your supply voltages.

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