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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Hi all. Does anyone here have any experience with these things? I have some CCCP VFDs with 3.6V filaments, the problem is that the datasheets are less than helpful when it comes to the correct voltages for avoiding phosphor damage.
Also is there a non destructive way to test them for phosphor degradation? Was thinking of using the "least useful" digit (ie LSB) or one of the decimal points which never gets used and then "thrashing" the tube with slowly increasing anode voltage over several days until the damage point is determined.
As I intend to use two in order to make a VFDPOV (tm) finding out the hard way that they burn out in a week would not be funny.
Any ideas? thanks! -A "Bother!" said Pooh, as the warp core required DOS 6.22 on floppy to enable the emergency eject...
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
When they burn out, does the filament open? What ever you are doing to the phosphor, that same current is being ripped out of the space charge and, when that can't balance the current, the emitting surface of the filament gets torn off, and ion bombardment provides more heat than If and it burns out. Perhaps you could chart the anode current against the anode voltage, and when that fails to obey the 3/2 power law, stop.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
I have only ever burned out one, it was an "eye" tube being driven literally beyond its thermal limit because it was very dim. Yes the filament opened. I am trying to avoid frying my tubes as buying more is going to be expensive.
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Care and feeding of small VFDs
