Numeridex Oak FTM Board Rebuild

User avatar
OldIsNew

14 Mar 2020, 02:28

I recently picked up a Numeridex 7000C2 keyboard. I haven't been able to find out much about the system it came with. The date code is 249-8219 so maybe 19th week of 1982?
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It turned out to be an Oak Full Travel Membrane board:

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When I tested the matrix it turned out that a number of keys didn't work properly so I decided to take it fully apart, clean it and see if I could reassemble it and get it working.
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Keyboard module:
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PCB:
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The switched are held directly to the metal plate by melted plastic rivets through the keyboard membrane. I used a wood chisel to cut off the rivet heads and remove the switches and the membrane.
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A plunger presses a central spring against the membrane to active the switches.
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The Shift Lock and Caps Lock are latching switches:
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The membrane parts are glued together so I did not attempt to separate them. When I tested the membrane out of the board, however, all the switches were working. After cleaning the membrane, switches and springs, I began to reassemble the board. I used clear silicone sealant (same as used as an aquarium sealant) to hold the switch pegs in the plate. I chose this because I found it held the switches firmly enough, but still allows for removal of the switches and easily cleans off plastic.

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To connect the membrane I used trio-mate 17pos connectors, breadboard pins and prototype board:
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Wired up the Teensy:

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Then reassembled the case. I did touch up the case with sage green spray paint which matched quite well. I haven't done the edges of the black front plate yet though.
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This is the matrix I came up with:
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The switches are linear, rather heavy and and overall I would say very "meh." It was still worthwhile imo, however, since I had never had the chance to try these switches before and it did make for a fun little project.

Quick video of banging away on board:

User avatar
JP!

11 Jun 2020, 17:54

This is way cool! So many rivets :o So I'd assume they server no real purpose?

User avatar
OldIsNew

19 Jun 2020, 04:52

JP! wrote:
11 Jun 2020, 17:54
This is way cool! So many rivets :o So I'd assume they server no real purpose?
Thanks! I thought it was sort of an interesting board. The rivets are formed from the four corner posts of each switch and hold the switches and membrane to the back plate so they are important. I used silicone sealant to hold the switch pegs in place when reassembling. An epoxy based glue would certainly hold them more firmly, but I found the silicone holds them adequately but still makes it easy to remove a switch if needed.

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