Fun with VFDs

[W9RAN]

I thought some of you might enjoy my experiments with a tube of a different color.  You may have read about using Vacuum Fluorescent Display (VFD) tubes in amplifier or oscillator circuits - I've been fooling with one in a Hartley and it works surprisingly well.  You can find some info here:

https://docs.google.com/?hl=en&tab=wo&authuser=0#folders/folder.0.0B98akUlPIomlYWE0YTlhZmYtYjJkNy00ODExLTgwYjMtYzM1ODMwYjZlZGVk

All VFDs seem to behave differently - and none work like we expect (just look at the transfer function curve).  But as long as there's power gain it'll oscillate just dandy - drawing about 3.5 ma from a 50 volt B+ supply for 170mW input.   It works fine on BC band thru 80 meters but I haven't tried to go any higher.  This VFD came from an old microwave oven control board, and has all anodes and grids wired in parallel.

At this power level, I get pretty decent-sounding AM audio by using a universal output transformer in series with the B+ as a mod transformer, with the 8 ohm winding driven from the output of a CD or MP3 player.   Makes a unique way to send old time radio programs around the house (or the Massacree, in four-part harmony!)

73 and HTD,

Bob W9RAN

[W7TFO]

Damn fine idea!  I guess a tube is a tube, be it flat with numeral displays or not.

That one looks to have a good curve for linearity with audio.

73DG

[kb3ouk]

I saw a few articles using these as audio amps but never anything like this. Wonder if you took enough of them that were identical to each other, and hooked them all in parallel , could you have a higher power transmitter?

[W2PFY]

I thought some of you might enjoy my experiments with a tube of a different color.  You may have read about using Vacuum Fluorescent Display (VFD) tubes in amplifier or oscillator circuits - I've been fooling with one in a Hartley and it works surprisingly well.  You can find some info here:

How did you ever come up with the concept? Something I would never given a thought but at the same time, I had no idea how those fluorescence's  worked in the first place. I'm still amassed and that takes some doing.

[Tom WA3KLR]

A triode is a triode.  Shhhh....don't tell anyone, the audiophools will find out.

A webpage by Hans Friedrichs AC7ZL:

http://www.hpfriedrichs.com/rr-vfd.htm

[kb3ouk]

I wonder if these can be paralleled (take 2 or so VFDs and tie all the elements together to turn the whole VFD into one big triode, then parallel the two VFDs together just like they were regular tubes) up to make a reasonable amount of power? a few of them together should put out close to at least half a watt or more. the only problem is you would have to have all of them being identical to each other. best thing would be to buy a batch of them that were all alike and go from there. there  may be some problems though that pop up when trying to run them parallel and also at higher B+ voltages.
shelby

[Opcom]

google wanted me to login and then showed me nothing. I got to it on another computer, how odd. VFDs are around here somewhere.. Where did I stack those old broken VCRs and alarm clocks? The nice thing about the idea is the colored glow and the possibility of using different segments and watching it work. Ths is a neat-o science project!