Replacement display for Datron 1271/1281 and possibly for 4950/4920 as well

[picburner]

Some time ago I bought a working Datron 1271 multimeter, but as has happened other times, the shipment was not painless: the right VFD display arrived damaged.
The packaging had been done well enough but the instrument had two very thin adapters on the sides of the front for rack mounting.
The blows received during the transport concentrated on these adapters and broke the little glass tube that was used to create the vacuum in the VFD.
This display is essential for some operations, so I first looked for a spare but soon I realized that it is practically unobtainable.
So I tried, through the signals generated by the instrument, to convert the bits dedicated to the switching on of the individual pixels of the original display into characters and symbols to be sent to an LCD or better an OLED.
After a few unsuccessful attempts I finally succeeded in using a "Bluepill" as a development board and writing a dedicated program in 'C'.
The photos show some menus of the instrument with a 4002OLED display but an LCD can also be used.
I also made the final pcb but I'm still waiting for it to be delivered to me (I finished it just in time for the start of CNY ....).

If someone else is in the same condition as me I can give the gerbers, the schematics and the code, but first I have to wait for my pcb and check that the front cover of the instrument closes without problems...

[doktor pyta]

picburner,
display substitutes certainly deserves a place here 
P.S. I didn't knew that finding suitable 1x40 VFD occurs to be such problem.

[coromonadalix]

Good job 

[guenthert]

     Hmmh, while it's a job well done, it's a pity that you lost the original VFD.  It's emerald and by far the most beautiful display of all my DMMs.

[TheSteve]

Awesome work! The vacuum port is hanging out in such a dangerous place. I've operated my 4920M during repair with the front plastics removed and that thing has "break me" written all over it. Please do share everything you've created as others will certainly benefit from it.
Maybe we can get a matching left side display made too at some point.

The original VFD's are very nice, and a rather unique color it seems.

[picburner]

@ doktor pyta:

The original display is an Itron DC405E2 and due to how the dot matrix is organized makes it difficult to replace with other VFDs.

[picburner]

@ guenthert:

I would have preferred the original display too but unfortunately I have no other choice.
However, the color of this 4002Oled is a little closer.

[picburner]

@ TheSteve:

Emulating the left side display is perhaps even easier using a graphical display and the stm32f103c8t6 has enough power to drive both.
At that point, however, it would be convenient to replace all the original pcb with a new one.

Yes, the two vacum ports are very very too close!

[MadTux]

If it fits, I'd simply rewire such a display with thin enamel wire
https://www.ebay.com/itm/Noritake-CU406ECPB-U2A-vacuum-VFD-display-/392966929744

[picburner]

Thanks for the warning but I have ascertained that the glass is longer: about 220mm against about 182mm of the original.
But the biggest problem is the different organization of the pixel matrix (in the original VFD the anodes of the first 20 characters are separated from the following 20 characters, in the newer VFDs are not) which would oblige me to modify the electronics too.
But at that point....

[picburner]

To highlight the problem mentioned in the previous post here is the solution adopted by a bbs.38hot.net forum user: he had to use two separate 20x2 VFDs.
In doing so, however, an empty hole remains in the center between the characters.

[coromonadalix]

If picburner solution works for him    goood   other will do their own implementation, even i  could not do better,  i'm good in electronics, do rewiring  etc ... but i'm bad at any coding or protocol sniffing

I helped quick1  complete his oled variant for the 34401a display, he was missing some data signal / timings etc ... and i had problems to make an cheap stm32 work at first  lolll


The graphical display advantage, its already wired and have the drivers on it, just need the stm32 as an interpreter

I think someone remade an complete front pcb for a datron calibrator and added more modern display


Maybe the @Madtux  Ebay  display could work or fit if the vfd section is pulled out and retrofitted on a new board ?? 

Some vfd's have began to be discontinued on some sites ....

[picburner]

Finally I have completed my project and, as anticipated, I publish the necessary files for the realization of the right display replica for the Datron 1271/1281.
As you can see from the images, using a blue OLED, you hardly notice the difference in tint between the original VFD display and the replacement one.
I had to do some small tweaks to the pcb, things you notice when you do the final assembly, so I was right not to post the files immediately.
You need two 5mm spacers (with 3 mm hole) between the original pcb and the new one and four 5mm spacers (with 3 mm hole) between the new pcb and the OLED panel.
The connections to be made are specified in the schematic.
To program the micro stm32F103 you need an ST-Link v2.
A forum user asked me in PM if it was possible to make a left display replica also: this is possible but I think it will take some time, at the moment I am a bit busy in other projects.

Note: The gerbers are made with JLCPCB rules.

[picburner]

Ah, I forgot to add a pic of the pcb which, due to some modifications, now it can be considered another  prototype (but for me it remains definitive).
The pcb dimension is 184x36mm.

[coromonadalix]

   looks like it was made like this

[doktor pyta]

beautiful 

[TheSteve]

Looks amazing! Thank you for sharing the design. I don't need it today, but tomorrow you just never know. The lab will always welcome more Datron equipment.

[chinapp]

waiting for the left display  project 

[pelule]

Grate job, hope to see more

[picburner]

For all those who are asking me here and in PM when the project of the other display will be ready:
I can devote only a little of my free time to this undertaking, so it will take several months, be patients.

[jfriend]

What was the P/N of the oLED display you used that had a very similar color to the original VFD?

[picburner]

I bought it on Aliexpress some time ago. The shop is this
In the description it says: SOC4002A.
Of course you have to choose the blue one.

[rigrunner]

That looks great.  Well done 

[jfriend]

I had a board made using the gerbers you provided and populated it according to the schematic. I successfully loaded the hex into the STM32. However, nothing happens when I connect the board to the VFD board. I've triple checked all the connections, they are correct. Turing my attention to the build, I don't read any crystal oscillation when using a 10:1 oscilloscope probe. My question is, is the hex up-to-date and has anyone else built one of these successfully? I'm not sure what else to test or check.

I noticed on your board photo R4 and R13 are not installed.

[picburner]

R4 and R13 are only needed if you're using an LCD display (Look at the schematic).
Crystal Y2 must oscillate at 8MHz otherwise U4 cannot work.
Y1 was needed for an unimplemented function instead, you can also not mount it.
Check the soldering of the U4 pins very well and that there are no jumpers between one pin and the adjacent ones with a microscope or a very powerful lens.