VFD Conversions as repair - Page 1
Forum section: electronics / projects

author: Richy_T
author_rank: Newbie
timestamp: January 24, 2022, 07:14:12 am
content: So I have a couple of devices where the VFD is looking less-than-fresh and it doesn't look possible to easily find replacement parts, particularly as it appears they're custom for the job. I know it's supposedly possible to over-volt them to bring a bit of life back to them but that seems like it could be error prone and with other similar kludgy solutions for other things (refreshing NICADs for example), it often seems short lived.So with the ready availability of cheap LCD displays on the market, I'm wondering about the feasibility of simply (or should I write "simply"?) dropping in something that intercepts the signals (probably some microprocessor) and generate the output on an LCD. Ideally, I suppose, it would be preferable to intercept the input to the driver chip (if such exists) or failing that, intercept the signals to the pins of the VFD itself.I have a rough idea of how VFDs function but not familiar with the details of the multiplexing, etc so I thought I'd run the idea out here first and see if there's any show-stoppers I'm missing. If it could be made generic enough, it could be a way to bring a lot of old equipment back to life. Potentially, it could even add functionality.

author: PKTKS
author_rank: Super Contributor
timestamp: January 24, 2022, 08:24:57 am
content: First thing is the VFD DRIVER ICTake note of the ic model and if possible the VFD BRAND and modelWith these you can possible find options to replace partsPaul

author: Haenk
author_rank: Super Contributor
timestamp: January 24, 2022, 09:32:46 am
content: Quote from: PKTKS on January 24, 2022, 08:24:57 amUsually, you can't. I'd say about 99,9% of all VFD were custom-manufactured. Cheap back then, unobtainable now.(Raising the voltage will not be a permanent solution, but might prolong the life for a couple of years...)

author: BradC
author_rank: Super Contributor
timestamp: January 24, 2022, 10:42:58 am
content: I did it on a Designjet750. The display on that had enough documentation to allow me to start to reverse engineer it and write a translator to a conventional LCD. The custom characters were a challenge and the Designjet also downloads customs into the display at various points so I had to translate those.It's doable but there are massive variations in displays and controllers so i don't think you are every going to get any form of universal drop-in.

author: PKTKS
author_rank: Super Contributor
timestamp: January 24, 2022, 11:01:48 am
content: Quote from: Haenk on January 24, 2022, 09:32:46 amWell YES if they are those kind of VFDs with funny things that act like LEDs kinda....REC.. PLAY.. DB (dolby) and RPM of other just ON/OFF segments..Volts... DC/AC.. etcetera...But.. if you have a VFD CHARACTER based in which you can drop in a suitable replacement per lines and columns... ITshouldor may work even with the builtin driver IC or.. if you replace the whole module with the proper IC attached and use a vanilla serial drive on it.Character based starburst segment or dot matrix may be replaced.. in full or partially...But getting the IC driver identification and perhaps VFD type is first step..Paul

author: PKTKS
author_rank: Super Contributor
timestamp: January 24, 2022, 11:05:01 am
content: Quote from: BradC on January 24, 2022, 10:42:58 amYES doable... and today it has become easier when you can adapt some small arduino or ESP32 board interface...Although the number of VFD screens is indeed high..The IC driver manufacturer list is SMALL and very specialized..which can make things easy when adapting interfaces..NEC.. Princeton.. SANYO..They are hardly over a dozen brands.. very specialized...Paul

author: Richy_T
author_rank: Newbie
timestamp: January 25, 2022, 12:19:22 am
content: These are definitely custom VFDs so there won't be a completely generic answer. What I was more thinking when saying "generic" was to have configuration files and maybe handle (or have the ability to easily add) several driver chips and potentially have some discovery functionality. It looks like intercepting the signal before the driver chip will be the way to go and the one I looked at (that is probably not one of the ones I need to manage but worth a look anyway) had a fairly simple serial input. (Data, clock, hold and blank).One of the displays I want to work with has quite a lot of dot-matrix characters so definitely would prefer not to work with that side of the circuitry.

author: PKTKS
author_rank: Super Contributor
timestamp: January 25, 2022, 08:57:19 am
content: Can you take shots?Paul

author: Richy_T
author_rank: Newbie
timestamp: January 25, 2022, 04:30:24 pm
content: I'll make sure to when I start digging into things. I'm more exploring it as a concept right now.