Driving Pinlite DIP-1050 alphanumerical filament displays/ minitrons - Page 1
Forum section: electronics / projects

author: Amper
author_rank: Frequent Contributor
timestamp: December 18, 2018, 01:12:34 am
content: Hi!A few years ago i got my hands on a lot of 5 of these amazing gold dust displays. Sadly they are so rare that i could not find any data on them so i decided to try my luck and just slowly power them up. They are just glorified lightbulbs so what could possibly go wrong? Well, they lit up but not evenly. The filaments start to softly glow in one place but over several tens of seconds that place shrinks smaller and smaller into a tiny hotspot until the segment dies. In my inexperienced youthful excitement i thought maybe they were faulty (tough very unlikely since they are NOS from starfighter avionics...) so i killed segments in two further units. Now today im left with three damaged ones and two in mint condition. Id really like to put them to use but im afraid to ruin more.So long story short: Does someone here have experience with this kind of displays? maybe some datasheet? Is there a trick to them? I tried to just apply the full (guessed) voltage instantly and even though the entire filament will light up evenly it still develops ireversable hot spots after just minutes.cheers

author: synare
author_rank: Newbie
timestamp: October 27, 2020, 01:35:41 am
content: I know this is an old topic, but I just came across it and thought I'd pass along some info in case anyone is still listening. These are terrific little pieces of electronics history.Like you found, there really isn't any info out there on these displays. I saved a pile of them from the trash a few years ago and had success in making a foosball table scoreboard from a couple of them driven by an arduino and other parts.They take ~5v and draw a fair amount of current, quite a bit more than LED displays. Maybe you gave yours too high of voltage or the cases were leaky and the filaments burned out, or maybe your circuit just couldn't supply the current needed? There really isn't much to them otherwise.Here are links to the only 2 sites I've found with pinout and power info:https://etalonelectronics.com/shop/drugi/bukveno-tsifrov-displej-s-nazhazhaema-zhichka-dip-1050a-pinlite/https://www.surplussales.com//bulbs-incan-panel/vacdisplay.html

author: Amper
author_rank: Frequent Contributor
timestamp: January 23, 2021, 05:18:25 pm
content: Hi!I dindt expect ever getting a reply, thanks for doing so!I have some smaller pinlites that work flawlessly, just this one type seems to have issues as i described it back then, i actually suspect it to be bad vacuum by now as i dont have any other explaination. I tried curret and voltage limited suppliy as well as slow or fast ramping when turning on but i never got them to work properly...

author: Ian.M
author_rank: Super Contributor
timestamp: January 23, 2021, 07:01:56 pm
content: That's the common behavior of a tungsten filament in an oxidizing atmosphere. Any small hot spot increases the rate of oxidization, and thus accelerates the loss of conductive cross-section, resulting in locally higher resistance and even greater heating at the hot-spot, causing run-away failure.

author: CaptDon
author_rank: Super Contributor
timestamp: January 25, 2021, 03:56:32 am
content: These are nearly identical to the RCA numitron displays. I have a military x-band signal generator that uses them. They were usually driven from the standard 5vdc TTL supply and I think mine are direct driven from a 7446/7447 if I remember correctly. They are indeed power hungry and make heat at about 50ma per segment if memory serves me correctly. Mine have a red filter in front of them to preserve night vision. I suspect yours have lost their vacuum at least partially.

author: floobydust
author_rank: Super Contributor
timestamp: January 25, 2021, 04:08:33 am
content: The incandescent displays are designed including the driver IC's output resistance (and voltage drop), for inrush limiting. Some datasheets even keep thempreheated.If you connect a display raw to a bench power supply, not good- as the inrush current (typically 10x operating) can damage the display, especially older ones with aged thinner filaments.

author: Amper
author_rank: Frequent Contributor
timestamp: January 25, 2021, 08:07:26 pm
content: I suspected so, so i tried even ramping them over several seconds, sadly to the same result.Im pretty sure they lost vacuum, though im not 100% convinced since all four behave exactly the same. Thats unusual for a bad seal. One way to find out would be to open one an put it into high vacuum but i dont really want to break it or good.

author: floobydust
author_rank: Super Contributor
timestamp: January 25, 2021, 09:19:01 pm
content: If they've lost vacuum, they will smoke inside and yellow-green soot. Or you have the wrong voltage spec for them?

author: Amper
author_rank: Frequent Contributor
timestamp: January 26, 2021, 03:33:11 pm
content: I know how burning filaments look like, im taing about a partial loss.Did you read my first posts?

author: floobydust
author_rank: Super Contributor
timestamp: January 26, 2021, 09:31:50 pm
content: Segments are rated 5V (TTL) 17mA, what did you get for current drain? With low or no vacuum at 5V the filament would draw much more current.I think the only way to guess what is inside is use high voltage and arc across a burned out filament, people judge the arc colour to tell if vacuum or air inside.

author: Amper
author_rank: Frequent Contributor
timestamp: January 27, 2021, 11:15:25 am
content: High voltage is a good idea, ill try that. Ill keep you updated when i know more.