Author Topic: Screwed Vacuum Fluorescent Display  (Read 664 times)

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Offline Foxtrot_95

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Screwed Vacuum Fluorescent Display
« on: March 10, 2019, 08:51:41 pm »
Hi everyone guys!
Recently I got a bunch of 6 IV-22 (ив-22), vacuum fluorescent displays, straight from a Moscow basement since the 80's to me, a strange guy who loves to mess with electronics, as a hobby.
My plan was to put a 6 digit clock together.
As soon as they came I went to the bench for some quality time testing them (never played with them before).

My setup consisted in two modules, step up and down, to get the proper voltages in order to make things work from a classic 12v power supply:
+30v for the screen grid and anodes and
+1.25v for the heater (maximum rating 1.32v)
Everything worked fine and I was very pleased to see the greenish super bright color of the digits.

But then, the s**t happened...
I didn't tested the tubes in their sockets, I just used flying wires and female headers on a breadboard to hook everything up.
A bad movement of the tube while powered up and a +30v rail touched one pin of the heater, making the tube glow bright orange for a second or less, I immediately cutted the power off.
Those soviet heaters are tough af, even after 30v were applied they didn't melt but the display now is very very dimmed :'(

How can I restore its brightness considering everything is still working?
I suspect a poisoning from heater elements getting flashed all over the segment anodes. Increasing the heater voltage helps with the brightness but at 1.5v it glows red hot and it's not cool to see.

You guys are my last hope before discarding it  :--
 

Online Gyro

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Re: Screwed Vacuum Fluorescent Display
« Reply #1 on: March 10, 2019, 09:11:43 pm »
Assuming that all of the supply rails are still as you expect, then you have probably evaporated off the emissive coating on the filaments.

The good news is that IV-22s are still plentiful and cheaply available on ebay. You haven't got your country flag set but I assume that you should be able to access these...

https://www.ebay.co.uk/sch/i.html?_odkw=iv-22&LH_PrefLoc=2&_sop=1&_osacat=0&_from=R40&_trksid=m570.l1313&_nkw=iv-22+vfd&_sacat=0


P.S. I just noticed - Welcome to the forum.  :)
« Last Edit: March 10, 2019, 09:13:56 pm by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 
The following users thanked this post: wraper, Foxtrot_95

Offline Foxtrot_95

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Re: Screwed Vacuum Fluorescent Display
« Reply #2 on: March 10, 2019, 10:26:39 pm »
Thank you, I just updated some basic info now, I'm a newbie :)

Yeah everything is still okay with the power supply, I just hooked up another tube and it displays fine.
I get the point  |O
I imagine I can't do anything to "clean" the segments even with higher voltages for long periods of time, and even if I manage to do so, the emissive layer of the heater would be so worn the tube won't last very long.

I understand IV-22s are very cheap and there are plenty of them compared to other past indicators, but still, this made me a bit upset because they took forever to arrive from Russia and it was a very stupid, yet unfortunate, accident.

I will replace it, peace!

Anything cool I could do with it apart from popping it?  ::)
« Last Edit: March 10, 2019, 10:28:40 pm by Foxtrot_95 »
 

Online Gyro

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Re: Screwed Vacuum Fluorescent Display
« Reply #3 on: March 10, 2019, 10:40:28 pm »
Yep, that sort of thing happens - it's a learning experience.

I was once building a clock with some nice dot matrix HP displays. I left the 50Hz timer interrupt input wire floating and it accidentally touched an exposed mains connection on the transformer. I blew a crater in the top of the 6805 micro, silvered the window of the EPROM and blackened the dies in all four displays!

No I can't think of any way of salvaging the display, in an ordinary vacuum tube you would try elevating the heater voltage slightly and pulling a heavy current on the Anode to expose a fresh emissive surface on the cathode, but in VFDs, the filament coating is designed to emit at very low temperatures and once it's gone, it's gone.

I suppose you could use it as a 'space model' for mechanically mounting the displays without worrying about damaging the seals.
« Last Edit: March 10, 2019, 10:42:23 pm by Gyro »
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline shakalnokturn

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Re: Screwed Vacuum Fluorescent Display
« Reply #4 on: March 10, 2019, 11:30:39 pm »
With the toasted display you could try keeping filament at normal voltage and raising anode voltage until you reach acceptable brightness.
 

Offline SpencerTC

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Re: Screwed Vacuum Fluorescent Display
« Reply #5 on: March 11, 2019, 02:39:38 am »
With the toasted display you could try keeping filament at normal voltage and raising anode voltage until you reach acceptable brightness.

You don't really have much to lose at this point, it's worth a try.

I'm sorry that happened, but as it was mentioned, it was a good teachable moment, I can't tell you how many projects/parts I smoked before I learned my lesson of insulating wires/pins before testing...I guess I'm a slow learner.

Good luck!
 


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