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I have an old keyboard (circa 1998) with a male DB9, and I'd like to use it on a modern PC with a female PS/2. The keyboard is AT&T branded, Comcode #405748401, FCC ID CIG8AVE03417 Keytronic corporation. I suspect, but I'm not certain, that the DB9 pinout is the same as an AT&T 6300: http://pinouts.ru/Inputs/KeyboardAtt6300_pinout.shtml. From that site I also found wiring pinouts for 5-pin DIN keyboard sockets and female PS/2 sockets, both of which seem compatible except the keyboard pinout shows +12VDC while the standard keyboard sockets show +5VDC.

Can anyone confirm the pinout for my keyboard? If it does match the 6300, can I just wire a DB9 to PS2 adapter and expect it to work? Am I likely to fry my motherboard if I get this wrong? This keyboard came from an old AT&T PC, and it's possible that the keyboard connector was proprietary or a serial port. I'd hate to damage either the keyboard or my new computer with a bad guess.

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    \$\begingroup\$ Why do you want to do that? \$\endgroup\$ – Leon Heller Nov 28 '10 at 2:42
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    \$\begingroup\$ This is one of the old style keyboards with a great feel to it. It was also my keyboard throughout college. I'd like to be able to use it again. \$\endgroup\$ – DougWebb Nov 28 '10 at 7:21
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    \$\begingroup\$ It was connected to an AT&T branded PC-AT computer circa 1988. The computer is long-gone. I've seen these keyboards online with PS2 connectors, so I think it should be a simple adaptor to make. \$\endgroup\$ – DougWebb Nov 28 '10 at 17:41
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    \$\begingroup\$ I've opened the keyboard up; it uses five wires in the cable, one of which is grounded to a large metal mounting plate for the keys. The other four (yellow, clear, brown, red if that matters) are in a plug-in connector on the circuit board that is mounted under the plate. There are a number of ICs on the board, the two large ones are an XR 22-00958-000 which I believe is a voltage regulator, and the other has Signetics and Intel trademarks: 20417-8, QFJ5219 8805KJ, 20-8031-0000. I'm guessing a micro-controller. There are two P8742/DM7404N ICs, and an 8-pin DIP switch that's set to all off. \$\endgroup\$ – DougWebb Nov 28 '10 at 20:42
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    \$\begingroup\$ I've emailed keytronic for help. Here's the full set of identifiers: The keyboard has the following identifiers on it: - FCC ID CIG8AVE03417 - AT&T SN 885303011589 - COMCODE # 405748401 - M/N E03417212 - P/N 34287 - S/N 1521381 \$\endgroup\$ – DougWebb Nov 28 '10 at 20:47
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I'd strongly recommend sending Keytronic an email on this one. They're one of the few who will know for sure without disassembling and reverse engineering what you already have. They'd probably be thrilled to hear from such a fan of their work!

I went through something similar with a heavy IBM tactile keyboard from 1984. The cable unplugged on both ends and was lost in a move, so I was looking for the pinout of their slightly squashed RJ19 looking connector. It was manufactured by Lexmark, and they helped sort me out via email after routing me to their 'old man on the mountain' keyboard guy. Sadly, it died it's final death about a year later from a close encounter with a four year old. I still hit the thrift stores once in a while looking for another to pop up, but I've pretty much adjusted to my $9-on-sale keyboard now.

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  • \$\begingroup\$ No luck. Here's their response: "Unfortunately the product you have is so old, we no longer have any of the specifications for the product. I’m sorry that we couldn’t be of more assistance." \$\endgroup\$ – DougWebb Dec 2 '10 at 1:59
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I think you'd need to positively identify what system that keyboard fit and what their protocol is like. Maybe you could make a microcontroller or other standalone circuit that would interface to that keyboard. Once you know what both sides expect and deliver, it should be easier to decide what an adapter should be like.

If you do want to experiment instead, you might want to get a scrap PC (motherboard) with PS/2 port and start working on attaching the keyboard to that. If you do happen to fry the PC, it wasn't a precious one. At least here, old computers are toxic waste that businesses are just dying to get rid of with least effort.

A nutty option might be to see if you can rewire that keyboard to be a genuine USB or PS/2 keyboard with modern internals but old keyswitch matrix.

Just try not to break the precious antique from better, vanished time :)

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