Recently, I had a challenge to find an XT compatible keyboard for a project I'm working on, a Tandy 1000 RL which I’ve covered previously on the bLog here.
I ended up going a couple of different routes on solving this problem, but the one I'll cover in this article is the Northgate Ominkey 101 that I found on eBay.
Northgate was a Minnesota based manufacturer of Clone PCs (A PC Assembler). They were profitable enough that they had their own custom designs being built for them, including keyboards. These are classic keyboards of their time, with a metal backplate, and "Complicated White Alps" mechanical keyswitches with a really great feel.
I stumbled across this keyboard while searching eBay for AT/XT Compatible Keyboards for my Tandy 1000 RL project, and the listing intrigued me. The seller indicted that one and only one key was not working. I was hopeful that I’d be able to fix the one key switch that was not working, and was able to get the keyboard with a surprisingly low bid. I was also able to find a full manual for the keyboard online and read through that information.
The first challenge was that this keyboard does not have an attached cord, so I ordered a PS/2 male to PS/2 male cable used on eBay so I’d be able to plug the keyboard in for test when it arrived. Also, I assumed that the reason one of the keys didn’t work was that it had a bad key switch, so I ordered 10 replacement keyswitches as well.
When the keyboard arrived, I tested it and it was indeed as the seller had stated, one and only one key did not work. Here’s what the keyboard looked like when it arrived...
I started by testing the continuity of the key switches with the ohm meter, and to my surprise the suspect switch was working, so I was not going to get the “easy win” with this keyboard. After poking around at the circuit traces, I remembered that the manual was very detailed. Going back and looking at the manual, it includes a complete circuit diagram for the board. Using the diagrams, I started to poke around more on the board testing continuity at various points, but after checking both the row and column that the key switch was on, I realized that the circuit diagram showed a small signal diode wired in series with each and every keyswitch on the board. After finding this out, I was able to isolate a fault, the small signal diode on the switch in question had opened up. I was able to repair this by putting another diode in parrallel, soldered to the back side of the board, since getting to the top side would have required completely dis-assembling the board.
Once I had the electrical problem resolved, I took all the key caps off, cleaned them with soap and water, and retrobrighted the key caps and top of the board. While I was putting the circuit board together, I noticed that the PS/2 connector inside the keyboard was broken. I tried to repair this with Superglue, but the repair failed because the glue filled the gap and I could no longer plug the connector in. Short term, I was able to make a keyboard cable by cutting off one end of the cable and soldering it directly to the board.
With the board both working and looking nice I was hoping to address a couple of small things, the missing keyboard door over the switches, the broken PS/2 connector, and the now missing cable. While googling around to learn about these keyboards, I had encountered this online buisness specializing in fixing up and reselling these boards. I reached out via email and the owner of the buisness was quick to respond, and he had all the parts I needed to get the board back to factory condition, and at a reasonable price. I’ve just installed those parts today, and I’m super happy with the keyboard.
Originally, I bought this board to use with an XT class machine, since I didn’t have any other options, but this keyboard has ended up looking so nice and having such a great feel that this will take its place on my desk as my “Daily Driver” for a while, replacing an Apple M0116...
Thanks again to Bob @ Northgate-Keyboard-Repair.com for the assist on this one, without his help I would not have been able to get the parts to return the board back to factory new condition.
Did you ever have a Northgate keyboard? Or what is your favorite keyboard from retro computing history? Please leave a comment below, or feel free to send an email.
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