Issues with 2WASZ keys on a Model F AT (and cleaning)

[derzemel]

I have managed to get an IBM Model F AT and I have an issue with it:
 - the keys 2,W,A,S,Z do not work (connected to PS/2 with a DIN-PS/2 cable).

Do you have any ideas?

As a first idea I took it apart to clean it... maybe this would solve the issue.

Here is the Imgur album with part 1 of the process, the teardown and starting to clean.

As a curiosity, it has flippers with 2 shapes. They are randomly placed:




Can this foam mat be reused? I wasn't falling apart, but it not very resistant either





Can I use 2mm thick foam rubber, like the one below, to replace the Foam Mat? If not, where can I find some Foam Mat?



I checked the strip continuity (hopping that this may be the issue with the 2WASZ keys). none of the strip wires are interrupted:



While Cleaning the PCB with Isopropyl Alcohol, I found 2 scratches:



and



In case the cleaning does not have any effect on the 2WASZ keys, do you have any ideas what may cause this issue?

Thank you!

P.S.: Tomorrow morning I'll finish cleaning the flippers and the barrels and reassemble it (as now is almost 2 AM)

[Sigmoid]

Hey, I hope I can help with this, as I've recently repaired an XT, and have read up a lot on Model F's.

I'm guessing that the different shaped flippers are from two separate generations... I have no idea if this means the keyboard has been restored using flippers from another, or IBM used a mix when they put it together in the first place. Cool though, I've never seen those rectangular ones before.

I'd replace the foam mat. It shouldn't be flat like this. And it will only get worse with time.

As for the scratches, from the photos it looks like they are only on mask on the PCB, the metal conductor seems intact... You can actually test a model F without the key assemblies themselves, just connect up the bare PCB to a computer, it will act as a capacitive TOUCH sensor. (If you poke the pads of a "key" with your finger, it should register as a keypress.)

Test 2WASZ (and other keys) like this, to see if it's the PCB or the assembly that was causing the problem.

[derzemel]

Hey, I hope I can help with this, as I've recently repaired an XT, and have read up a lot on Model F's.

I'm guessing that the different shaped flippers are from two separate generations... I have no idea if this means the keyboard has been restored using flippers from another, or IBM used a mix when they put it together in the first place. Cool though, I've never seen those rectangular ones before.

I'd replace the foam mat. It shouldn't be flat like this. And it will only get worse with time.

As for the scratches, from the photos it looks like they are only on mask on the PCB, the metal conductor seems intact... You can actually test a model F without the key assemblies themselves, just connect up the bare PCB to a computer, it will act as a capacitive TOUCH sensor. (If you poke the pads of a "key" with your finger, it should register as a keypress.)

Test 2WASZ (and other keys) like this, to see if it's the PCB or the assembly that was causing the problem.

Thank you!

I have replied to your post on DT

here is the link to the DT topic, in case someone else is interested: http://deskthority.net/workshop-f7/issues-with-2wasz-keys-on-a-model-f-at-and-cleaning-t10621.html