How to check if capacitive layer is damaged in Model F?

[snarfarlarkus]

Hey guys, my Model F keeps ghost typing random keys and even some keys don't work. The only fix would be to go into the IBM cap sense program and change the voltage between 110 - 130. Its very annoying and I've posted here before regarding this to clean the inside to get rid of dust and debris. I've opened it up again and it is completely clean.

So just wondering how I could fix this? Maybe the capacitive layer is going bad?

[y11971alex]

That's not very likely, unless you can identify by the naked eye some kind of irregularity on the pad card.  The pad card is one of the most robust components in the entire keyboard, and the only thing that can injure it is corrosion. 

[fohat.digs]

Did you replace the foam mat? This type of symptoms have troubled me occasionally but it is usually because the plates and parts are not being held together firmly and consistently across the surfaces. That is why I add 2-4 bolts in the center of the curvature when I do a refurbish. Tightening everything up snug has always taken care of the problem for me.

[chyros]

Definitely sounds like a spacing issue. Although easily reparable, the capacitive system in Model Fs is really sensitive to changes.

[snarfarlarkus]

Did you replace the foam mat? This type of symptoms have troubled me occasionally but it is usually because the plates and parts are not being held together firmly and consistently across the surfaces. That is why I add 2-4 bolts in the center of the curvature when I do a refurbish. Tightening everything up snug has always taken care of the problem for me.

No I didn't replace the foam mat unfortunately. I don't know where to get one that I can directly replace?

[fohat.digs]

where to get one

Oh, you are a funny boy.

https://geekhack.org/index.php?topic=48786.msg1048948#msg1048948

[snarfarlarkus]

where to get one

Oh, you are a funny boy.

https://geekhack.org/index.php?topic=48786.msg1048948#msg1048948

Haha thanks for that! Such an amazing write up.

Before I may potentially try this, if I somehow screw up fully disassembling the plates will I damage the board permanently? Seems very risky.

[fohat.digs]

if I somehow screw up fully disassembling the plates will I damage the board permanently? Seems very risky.

These parts are extremely robust and it would be very hard to damage any of them.

Re-assembly - that is - squeezing the layers back together and making the "sliding force fit" work again is the only tricky and difficult part of the process, the rest is just fussy and time-consuming.

[snarfarlarkus]

if I somehow screw up fully disassembling the plates will I damage the board permanently? Seems very risky.

These parts are extremely robust and it would be very hard to damage any of them.

Re-assembly - that is - squeezing the layers back together and making the "sliding force fit" work again is the only tricky and difficult part of the process, the rest is just fussy and time-consuming.

Thank you. I might give it a try.

[Wingklip]

if I somehow screw up fully disassembling the plates will I damage the board permanently? Seems very risky.

These parts are extremely robust and it would be very hard to damage any of them.

Re-assembly - that is - squeezing the layers back together and making the "sliding force fit" work again is the only tricky and difficult part of the process, the rest is just fussy and time-consuming.

Thank you. I might give it a try.

It's guaranteed to not explode. I did mine using a soldering iron and ldpe close cell foam

[SneakyRobb]

My first model f I removed the little siders from the metal plates. I used screws to hold it together. 
Immediately it had severe ghosting issues, just from the change in how the plates were attached.  I have never removed the sliders since on any model f keyboard.
I could touch the keyboard and it would spray out keys for a few seconds. It was also extremely clean inside. On model f the original foam can deteriorate and lose its special foam abilities over time.

 I agree with fohat that it is unlikely your board is damaged.
You should follow his foam guide.
It is important that the barrels are held in place with the foam. The foam is no joke, an absolutely critical component of the model f.

Foam.

[fohat.digs]

My first model f I removed the little siders from the metal plates. I used screws to hold it together. 

It is important that the barrels are held in place with the foam. The foam is no joke, an absolutely critical component of the model f.

If you did this based on my old original deprecated guide I sincerely apologize. I did it once and it worked great, I still use the board sometimes, but the next time I tried it was a disaster.

What I did take away from that process was the notion of adding a few bolts down the center line of curvature, and that really helps. For the last few years I have used 4 on a 122-key: (1) in the center of left-F6, left-F8, CapsLock, and Left Shift, (2) between upper 5% and upper F5, (3) between upper 0) and upper F10, and (4) right of Enter diagonally above left arrow - each located by eye on the PCB first in order to miss the traces!

With those extras screwed down tight, any chattering and ghosting goes away.

[SneakyRobb]

My first model f I removed the little siders from the metal plates. I used screws to hold it together. 

It is important that the barrels are held in place with the foam. The foam is no joke, an absolutely critical component of the model f.

If you did this based on my old original deprecated guide I sincerely apologize. I did it once and it worked great, I still use the board sometimes, but the next time I tried it was a disaster.

Apology accepted and no hard feelings. I did follow your guide dutifully grinding away the tabs. I did later see you updated it talking about the tabs. Lesson learned, and still got many teachings.
 Luckily I did buy that board, an XT "bigfoot" specifically as a sacrificial learning board, accepting before hand that I might end up destroying it. So that when I did my FXT and then FAT I would be less likely to fail.

 The rest of your guide and comments have given me many keyboard teachings.

[0100010]

Model F ghosting with an xwhatsit controller can usually be cleaned up using the alternate debounce filter.