Having problems with my IBM Model F?

[snarfarlarkus]

So I've owned my Model F for a few years and and this problem has persisted ever since my ownership but I just dealt with it but its getting really annoying now as its getting worse and happening more.

The problem seems to relate to the voltage threshold of the capacitive switches? Some keys on the keyboard just won't register and I have to play around with the voltages more and more to get them to work and sometimes they won't even work, period. Then the next day they will then the next they wont. Pretty annoying. I use IBM Capsense USB Util to change the voltage threshold and I change it every couple of days between 112 and 130. When I first got the board from the previous owner, he said 120 was the sweet spot and it was for a short while. I might need to get an updated version of the programme but cannot find it.

So can someone please help to mitigate this problem? The Model F is probably my favourite keyboard in terms of keyswitch feel but man, changing that voltage every couple of days and most times a couple keys dont even work make the F unusable. Thank you so much!

[y11971alex]

Have you tried cleaning the sensing board?  Capsense can be sensitive to dust &c.

[chyros]

Is the PCB held tight enough to the barrel plate? Are all the screws tight and good? Is the grounding wire connected properly to the back panel? The Model F is highly sensitive to electric variations.

[snarfarlarkus]

Is the PCB held tight enough to the barrel plate? Are all the screws tight and good? Is the grounding wire connected properly to the back panel? The Model F is highly sensitive to electric variations.

Have you tried cleaning the sensing board?  Capsense can be sensitive to dust &c.

Thanks guys. I've opened up the board a couple months ago and it seemed to be pretty dust free as the previous owner sand blasted the plate. I'll open it up again and see if there is any dust. What board am i meant to be looking at when disassembling?

[fohat.digs]

The first easy step is to ensure that the controller board is securely grounded to the chassis. That is the one with the gray ribbon cable.

There are 2 screws that hold it tight to brackets. Then check to ensure that the tabs that hold the plates together are all seated and tight.

[Hypersphere]

The only time I had a problem with keys not registering on an IBM XT keyboard was years ago when I got in a hurry and put washed keycaps back on the board before they had completely dried. I discovered that the switches are highly sensitive to moisture. As soon as they dried out, the keys registered again.

[chyros]

The only time I had a problem with keys not registering on an IBM XT keyboard was years ago when I got in a hurry and put washed keycaps back on the board before they had completely dried. I discovered that the switches are highly sensitive to moisture. As soon as they dried out, the keys registered again.

Mine stopped working just because I didn't tighten one of the bolts enough. It's incredible how sensitive these switches are to EVERYTHING.

That said, if you don't **** around with it, there's little that can go wrong with them, let alone anything that can't be fixed.

[snarfarlarkus]

Hey guys, just opened the F up again and checked if everything was grounded properly. The gray ribbon pcb is only tied down to the plate with one screw as the other screw hole does not match the screw hole on the plate. I've tightened the screws extra tight in hopes of it helping but the F still isn't 100% functioning properly yet unfortunately. Any other ideas? Thanks
'

[fohat.digs]

The controller has 2 screws on the 122-key, I suppose that you have one of the small ones.

If your problem is truly "electrical" I have nothing more to offer. But if your problem is "mechanical" then there might be a fix at the work bench.

If the problem keys are all in a limited specific area, I would look at the possibility that the plates are either loose or too far apart in that area, and try to figure out how to tighten them up.

If it is happening randomly all over the place, it *may* be a situation where the foam has deteriorated and is no longer doing its job of separating and padding and adding compression between the plates.