"frank" wrote in message
...
Hi all,
has anyone ever seen a VFD (vacuum fluorescent display) failure in which
half
the display is very dim and the other half looks good?
I have this 16 character (16 segments) 1 row display and the first 8-10
characters have a normal brightness, the rightmost ones are very dim,
barely
readable.
I first suspected a problem with the filament supply, but swapping the
filament pins has no effect, so I'm a bit puzzled.
Waveforms look identical on all the 16 grids too.
Unfortunately I have no schematic of this instrument (digelec 824 eeprom
programmer), nobody else in the world seems to have this programmer also,
so I could not ask anyone for some quick waveform comparison.
I'm starting to suspect a bad VFD but I can't imagine how would it fail
like this.
Part of the filament supply is made with a NE555 that's getting quite hot
and also a 120 ohm 1/4W resistor near it gets too hot to touch, but all
components I could test looks ok. I swapped the 555 and it doesn't make
any change. If I leave the 555 out, the display has no filament supply.
Any hint is really welcome.
Regards

Frank IZ8DWF

You might take a look at this:

http://www.eevblog.com/forum/chat/va...-rejuvenation/