IBM Model F Key problem

[anmq91]

Hey guys, I know there is a post talking about a key on the model F getting stuck, but in that case the key is getting stuck on the upstroke. My problem is a little different and weirder.

I've got a fully rebuilt Model F AT that runs wonderfully. I replaced the foam as well and cleaned the whole board. All was fine for a couple of months but now I noticed that only on the '7' key on the numpad, there is a new problem. When I press the key, the spring buckles (I know this because I can hear and feel the tactility as the spring gives), but the flipper doesn't move and contact the PCB until I press it 3-4 times repetitively. After I do this, the flipper starts to work when the key is depressed and the sound and feel of the key become exactly the same as all the other keys on the board (When the flipper is stuck it is a little more muted and not very pingy). If left alone for ca. 30 seconds, the flipper gets ' stuck' again and requires the key to be pressed a few times in order to 'loosen' it up. It's almost as if it's sticky, but not sure how that would be possible seeing as the board is newly cleaned and not had anything in/on it since.

Not sure what to do, and it is annoying because I do use the numpad occasionally and I am hoping there may be a quicker and easier fix to this than having to open up the whole board again just to fix this one key, which is only partially defective. Any ideas or help would be highly appreciated!

[SneakyRobb]

Hey guys, I know there is a post talking about a key on the model F getting stuck, but in that case the key is getting stuck on the upstroke. My problem is a little different and weirder.

I've got a fully rebuilt Model F AT that runs wonderfully. I replaced the foam as well and cleaned the whole board. All was fine for a couple of months but now I noticed that only on the '7' key on the numpad, there is a new problem. When I press the key, the spring buckles (I know this because I can hear and feel the tactility as the spring gives), but the flipper doesn't move and contact the PCB until I press it 3-4 times repetitively. After I do this, the flipper starts to work when the key is depressed and the sound and feel of the key become exactly the same as all the other keys on the board (When the flipper is stuck it is a little more muted and not very pingy). If left alone for ca. 30 seconds, the flipper gets ' stuck' again and requires the key to be pressed a few times in order to 'loosen' it up. It's almost as if it's sticky, but not sure how that would be possible seeing as the board is newly cleaned and not had anything in/on it since.

Not sure what to do, and it is annoying because I do use the numpad occasionally and I am hoping there may be a quicker and easier fix to this than having to open up the whole board again just to fix this one key, which is only partially defective. Any ideas or help would be highly appreciated!

Hi happy to hear you have a F AT. What a great thing.

Some questions to help solve issue.

What kind of foam did you use.

As well have you removed the keycap to look at the spring inside?

My main thoughts are basically if you don't want to disassemble the board, to remove the cap, look at the bottom of the cap. Look into the barrel and at the spring and examine for any obvious reasons.

Maybe try a different keycap on the barrel to see if you can replicate the issue.

Post the photos here with good lighting.


If you cant quickly solve then you probably will need to take apart.


In general the vast majority of model F click problems can be solved by:

1 removing the keycap, shaking the board a bit, and putting it back on.
2 disassembling and reassembling the board

[anmq91]

Hey Sneakyrobb, thanks for the quick reply. I used 1.5mm Neoprene foam that I bought off eBay. It fit perfectly and closed snuggly. It has vastly improved the consistancy of the switches accross the board. Someone from the forum suggested to use the 3mm Neoprene, but I felt like that may have been tough to get closed again.

I took off the keycap and put it back on many times, it unfortunately didn't solve the problem so far. The spring looks normal (at the same angle and depth as the other ones on the board. As per your advice, I just took the keycap off and gave the board a good shake upside down before putting it back on. It seems to be working for now, but testing it after a few hours of it sitting is the only way to make sure the problem is gone for good.

I'll update here in the morning, and if the problem is still there, post pictures as well. Thanks again for your help!

[-Space-NATO-]

Im restoring an AT right now, i'll be using a 2mm thick foam. I'll tell you what i found when i assembly it back together. Did you clean the pads with some IPA??

[Weezer]

My thoughts mirror Robb's. The old foam is often a sticky paste and I've had flippers get gooed up in what sounds like a similar way, with foam goo inside the crook of the barrel where the flipper sits. It likely needs to be taken apart, examined and cleaned. Try your best to not dump the flippers everywhere as having the flipper and barrel that corresponds to 7 will help you deduce the issue.

[anmq91]

@ Weezer- Ahh yeah I never considered the fact that the old foam was actually really sticky. I did manage to get out all of the flippers before even starting to touch the foam, but it could be that some goop got on that one I guess. After doing the shaking trick, it sticks a little less than before, but still needs to be pressed twice to get it to start registering.

@ Space-NATO-, nopes I didn't use IPA. I cleaned the barrels and plate etc thoroughly and then put the barrels with some dish washing liquid into an ultra sonic cleaner. I was afraid to mess with the flippers because they are made of some special plastic and I didn't want to take a chance on ruining their capacitance.

For the reassembly; if this is your first time, do consider buying some cheap clams from the hardware store to help getting it back together. But for sure, do let us know how it works with the slightly thicker foam.