IBM Model F output invalid keypresses

ryvnf

18 Jun 2020, 15:02

Hello!

I'm working on restoring an IBM Model F bigfoot using soarers converter firmware. The controller is working but the key presses which are outputted are slightly wrong.

For example, when I press the R key, the computer receives "ER". When I press "4" the computer receives "35". This pattern where nearby keys are registered occur for all keys in the keyboard. Pressing some keys like "O" will spam "IO" super quickly until the key is released.

Anybody know what could cause this issue and how it can be solved?

I was thinking maybe it is the foam which has deteriorated. Or could it be some threshold settings being wrong? This is my first restoration so it would be nice if anybody who has gone through this before could explain what is probably wrong.

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zrrion

18 Jun 2020, 21:36

from what I remember when I set up a converter for the bigfoot, most of what the soarers controller is doing is multiplexing and it really isn't doing any capsense itself as that is handled by the bigfoot. If you are comfortable with it you could take it apart and check the foam but I'm not convinced that the foam is related to your issues (my foamless XT doesn't have any problems.) You could also check any capacitors to ensure that none of those are failing as that might cause issues.

Fkazim

20 Jun 2020, 14:56

I had this exact problem with one of my Model F's. It was dust in the capacitive PCB.

After I opened the assembly and cleaned the capacitive PCB the problem went away.

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DMA

24 Jun 2020, 23:50

Fkazim wrote:
20 Jun 2020, 14:56
I had this exact problem with one of my Model F's. It was dust in the capacitive PCB.

After I opened the assembly and cleaned the capacitive PCB the problem went away.
This. Dust, bread crumbs, foam granules - turns out those flippers must stay really close to the PCB, even small particles halve the signal level.

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