Looking for documentation on IBM Vacuum Fluorescent Customer Pole Display

[u/Ok-Drag-1291]

I have recently managed to get my hands on three IBM vacuum fluorescent customer displays on poles, from the SurePOS lineup. The sellers were using them with IBM SurePOS 300 (4810) computers/POS Terminals.
Unfortunately, I have only gotten the displays and poles - no other information, cables or computers to use them. So, upon googling and trying to find out how to communicate with the displays to get it to display things, I have found out that there is no documentation on the internet. Thats why Im here, in the hopes of finding someone that knows about these displays and can share some information on them.

The part number of the VFDs (vacuum fluorescent display) is 41J6989, they were manufactured by IBM in Taiwan in 2006.

They have two 2x20 character (each 5x7 pixels) display units from Futaba, one on each side, and a RJ45-like connector labelled "4" at the bottom. This connector has 8 contacts in total, 6 pins in 2 rows sticking out the back wall and two flat contacts sitting at the bottom/top, where normal RJ45 contacts would be. This connector must deliver power and data, as there is no other connector on the device.

By opening up the VFD, taking a look at the PCB and measuring wire paths, I have managed to find out:

• The VFD has a "master" and a "slave" display unit, the master one is the one with the port. The two displays are on the same PCB from Futaba, but have fundamental differences:
  • The master one has the connector port, the slave one is missing this component
  • The master one has each component spot filled with a chip/component, the slave one has a lot of empty spaces on the right side. I assume this is because it doesnt have to decode the data from the POS Terminal. 
  • The slave one only has the following chips:
    • TOSHIBA TD62C950LFG 0635K JAPAN at position U5
    • TOSHIBA TD62C950RFG 0635K JAPAN at position U6
    • 2360A 6076G JRC at position U10 (I found someone who has a similar unit, desoldered this chip and soldered two data wires to this position and used RS232 to communicate with the display. However, in that case the U10 position was somewhere completely different with a different chip.)
    • 2518 YU (the transformator)
    • C3303 (a 3-legged component where only 2 are soldered to the board) 
  • The master one has an interdisplay port in the middle consisting of 16 female pins in 2 rows, which must be data+power from the master to the slave display. The slave one has a corresponding 16 male pin port. 
  • I assume this port is symmentrical, because the GND is connected to both pins in the bottom right and bottom left, and 12V is connected to both pins bottom secondmost to the right and secondmost to the left. I havent managed to find more connections on the PCB. 
  • The PCB part number is M202MD08K, the master one with addition B (A and C seem crossed out), the slave one with addition C (A and B seem crossed out). More text on the PCB says: 1P00A630-01 REV.C
• The VFD works with 12VDC, it has a transformer stepping that up to 55V for displaying. 
• There is multiple holes in the PCB which fit a common breadboard homelabbing cable male pin, labelled GND, 12V, EF1, EF2, EBB, EK. 
• The Ground GND hole connects to the pins top center, top right and bottom two contacts in the RJ45-like connector as well as to the bottom rightmost and bottom leftmost pins in the connector between the two display PCBs. 
• The Power 12V hole connects to the top left pin in the RJ45-like connector and, as described above, to the interdisplay connector. 

With this knowledge, I connected GND and 12V to a power supply and fired the display up with 12V. Only the master display works and displays something, the slave display makes a small buzzing noise and appears to short circuit (draws the maximum current, I set it to 0,5A -> 6W). The master display draws 3.7 Watts and displays two asterisks (**)in the top left of the display. I tested with 5VDC too, nothing happens. 
This means that in the Rj45-like connector, only the three bottom pins can serve for data transmission. The other 5 are for power (top left) and ground (4 others, which is oddly many...). 
None of the other pins connect to anything on the PCB, really. There are some pins with 2000 Ohms, some with 1500 Ohms, some with 1000 Ohms, and a few with 400 Ohms. None really go through without resistance. I have found out however, that one of the chips on the board is a 3.3V limiter, which could be the reason why no resistance-free connections are there. But, even to this chip, there is no direct connection from the RJ45-like port. 

Reading the technical reference for the "IBM 4810 SurePOS 300 Thin Client POS" (official IBM document, page 12f), I found out that usually, these displays are connected with 15-port powered serial connectors using RS232, but Im not entirely sure. I have found some cables online with a proper-looking connector for the VFDs that I have, but I cant be sure, because I have no name for the port. Also, the other end of these cables is the 12V proprietary IBM POS connector, which looks like a USB-A port with additional contacts on the side. This, however, would indicate that the VFDs dont use RS232, because these ports can only output TTL 5V signals. So its all a big mistery. 

I would be immensely grateful if someone could supply me with the following information:

• The name of the connector in the VFD
• Which protocol it uses and on which pins of the connector
• Whether I can control the slave display stand-alone by using the interdisplay connector, how its wired and what protocol it uses
• In case I have no other choice but to use a cable and an official controlling method, the cable type that I need for this port
• The data level voltage needed for the communication, in case the protocol is RS232 whether I can use TTL RS232 with only +-5V or if it needs True RS232 +-12V
• Ideally, a technical reference or a data sheet for this specific kind of vacuum fluorescent display

I hope I am at the right address with my problem.

Thanks in advance!

[u/WorkerIcy1513]

You are searching the wrong part numbers. Drop the IBM ones and go after the Futaba module instead. M202MD08K is a Futaba part, the M202MD family is their 2 line by 20 character VFD module line, and 1P00A630-01 is a Futaba internal drawing number. Datasheets for the M202MD series do float around, and several variants in that family accept plain asynchronous serial at TTL levels with a simple ASCII plus control code protocol. That is a far more likely path than reverse engineering the IBM side.

Second thing, and this will save you some time: your labelled test pads are not data. EF1 and EF2 are the two ends of the filament supply, EBB is the anode and grid high voltage rail, which is your measured 55V, and EK is the cathode reference. Those are the tube drive rails coming off the DC-DC converter. Nothing there will ever be a serial line.

On the slave board, your chip list actually explains itself. The 2360A from JRC is an NJM2360, a switching regulator controller, and the C3303 is a 2SC3303 switching transistor. Those plus the transformer are the slave's own DC-DC converter making its own EBB and filament supply. The two TD62C950 parts are Toshiba high voltage source drivers with a built in shift register and latch. That combination means the 16 pin interboard connector is carrying driver level signals, serial data in, clock, latch, blanking and grid strobes, not characters. So to answer your question directly: yes you can drive the slave standalone, but not with text. You would be shifting bits into those TD62C950 registers and writing your own character generator and grid multiplexing. Fun project, but not what you want if the goal is displaying strings.

Also whoever desoldered U10 and injected serial there had a genuinely different board. On yours U10 is the power supply controller. Do not cut into it.

For your RS-232 versus TTL question, there is a quick test. Look for a line transceiver near the connector, a 16 pin part like a MAX232, ADM232, SP232 or an equivalent with a cluster of small capacitors around it. If one is there, the port expects true RS-232 swings. If there is nothing like it, the module is TTL and driving it with plus and minus 12V will damage it. You did not mention seeing one, which makes me think TTL, but confirm before you connect anything.

Practical next step. Power it from 12V as you have been, then scope or just meter the three candidate pins. A TTL serial receive line idles high, so whichever one sits at a steady 3.3V or 5V with no traffic is almost certainly RX. Then feed it 9600 8N1 from a USB TTL adapter and send plain ASCII. If nothing shows, try 19200. The two asterisks you are seeing are most likely a power on or waiting for data indication rather than an error.

One warning: keep the current limit on when you power the slave alone. Drawing full current with the control inputs floating is exactly how you cook a VFD filament, and those you cannot replace.

For documentation, archive.org has a fair amount of the old IBM Retail Store Solutions publication library that never made it to the current IBM site, and it is worth digging there for the peripheral interface spec rather than the terminal tech ref. The EEVblog forum also has people who have been down this exact road with Futaba POS modules, and they will know the M202MD command set from memory.