Thanks John,

> A VFD is basically a triode vacuum tube, so you'll also need to bias th=
e> cathode.  The VFD filament usually doubles as the cathode ("directly> =
heated cathode" in vacuum tube parlance).  The cathode voltage is> typica=
lly applied via a filament transformer center-tap.

> In a product I designed many years ago I connected one end of the VFD> =
filament directly to the cathode bias voltage and drove the filament> wit=
h a square wave applied to the other end through a DC blocking> capacitor=
, thus eliminating the filament transformer.  If you try that> trick be s=
ure you don't exceed the VFD inter-element voltage maximums,> as the driv=
en end of the filament will almost certainly have larger> voltage excursi=
ons relative to the other tube elements than encountered> with a center-t=
apped transformer drive.
I have an old VFD tube (FIP8A5R) that I'm experimenting on. The tubeis a =
8 digit 14 segment alphanumeric display.
I connected a 3V battery on the filament and it started to glow thatmeans=
 that it is rated below 3v. Later I connected the G1 (grid ofdisplay1) an=
d a segment to positive terminal of the battery. A segmenton the display =
1 should have lit but it didn't.
As you have stated (and mentioned on Noritake's website) I need todrive t=
he filament with a square wave. So I would connect one pin ofthe filament=
 to ground and the other to ~50hz square wave output of amultivibrator. A=
nd to light up one segment of a display, I wouldconnect the display grid =
to +v and the segment to +v, is that correct?
   Seg-a +ve    | -------------------|                /- |-----| |---- FI=
L1 _|=A1=A5|_|=A1=A5|_|=A1=A5|_|               |   ||                \ -|=
------------- FIL2 -ve--------------------    |   G1+ve
Thanks,
--Chetan BhargavaWeb: http://www.bhargavaz.netBlog: http://microz.blogspo=
t.com
--=20
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