Key Strangeness of an IBM Model F

[Coeus]

I have an IBM Model F which, mechanically, has been working fine. Last night, though, the B key stopped clicking and was bit and miss as to whether it would register. I popped the cap off and also the N key to compare. The N looked as I would expect with the spring sloping noticably towards me. For the B key the spring still had a slight slope but not as much, i.e closer to upright. I nudged the bottom of the spring with a small screwdriver and now it is clicking and working fine again.

So I suspect the flipper might have moved slightly to cause the problem and has now moved back. What would cause that? Foam that has lost it's elasticity?

I did take this apart when I first got it to clean it and treat the rust on/paint the barrel plate. With the exception of needing to search and find the fishing line trick for the space bar it went back together very easily - was it perhaps too easy as other people report needing clamps and I just used by hands? I did have all the caps off but I assume that's normal.

When I had it apart the foam had not disintegrated - it still held together in one sheet but the surface that had been in contact with the barrel plate was slighly tacky and would leave black marks on your fingers when touching it. Does that mean it should really be replaced?

[kbdfr]

Aaaaand… still another thread reporting IBM problems.

Apparently IBM stuff’s reputation of being high quality, world class, premium equipment does not suffer from all the flaws.

This being said, I do not doubt (and certainly hope) numerous DT members will be able to help you with your issues.
They have gathered enough experience, after all

[ddrfraser1]

Bit of a chip on your shoulder there kbdfr?

[hellothere]

My opinion. The Model F has two problems:

* Foam.
* Having to sandwich the back plate to the barrel plate. There is NO compelling reason to have that design. Just line up the plates properly and screw 'em together. That's all you need.

The Model M has one problem: plastic rivets. Sure, that saves money. That doesn't make me feel better when I have to take one apart for a bolt mod. Heck, I've been working on other projects because I really don't want to do that bolt mod on my Model M 122.

Anyhow, Coeus, the foam is there to hold the barrels snugly in place. If there's a lot of wiggle in the barrels, yes, you probably need new foam. It's also possible that you have some of that foam residue on the membrane plate. That happened in my case. Considering I have all of one Model F restoration as experience, I don't know how often this happens. I've seen pics and vids where the foam has turned to dust. I've also seen pics and vids where people don't use a foam insert at all.

[PlacaFromHell]

Aaaaand… still another thread reporting IBM problems.

Apparently IBM stuff’s reputation of being high quality, world class, premium equipment does not suffer from all the flaws.

This being said, I do not doubt (and certainly hope) numerous DT members will be able to help you with your issues.
They have gathered enough experience, after all

Good luck expecting the same aging of other 30+ years old products, also featuring the same reparability of such modular designs where the switches are not even soldered. It seems that someone would like to age at the rate that IBM keyboards do

[Inxie]

My opinion. The Model F has two problems:

* Foam.
* Having to sandwich the back plate to the barrel plate. There is NO compelling reason to have that design. Just line up the plates properly and screw 'em together. That's all you need.

The Model M has one problem: plastic rivets. Sure, that saves money. That doesn't make me feel better when I have to take one apart for a bolt mod. Heck, I've been working on other projects because I really don't want to do that bolt mod on my Model M 122.

Anyhow, Coeus, the foam is there to hold the barrels snugly in place. If there's a lot of wiggle in the barrels, yes, you probably need new foam. It's also possible that you have some of that foam residue on the membrane plate. That happened in my case. Considering I have all of one Model F restoration as experience, I don't know how often this happens. I've seen pics and vids where the foam has turned to dust. I've also seen pics and vids where people don't use a foam insert at all.

There is a reason for this actually. Remember the Model F is capacitance. Grounding and shielding is VERY VERY important.

For example, today after cleaning my Model F in my other thread (the one I'm typing this on), I had some issues at first when done. It was typing random characters by itself. It wasn't until I noticed that one of the screws I didn't tighten all the way. This was the one that grounds those two metal plates and the back metal cover itself. That wire got lose, and all it did was ground the metal plates, and it was causing random phantom keystrokes (like 9 at a time even).

So yea, it's kinda an important part of the Model F design.

[hellothere]

Not trying to be snarky. I'm not an electrician in any way, shape, or form, am I understanding you correctly that you're saying the foam is necessary so you don't have a short? If so, the guy in this video doesn't use foam at all and it works fine (see also the comments).

In my build, I noticed a grounding wire from the cable to a non-painted screw hole on the bottom case and another screw that held the circuit board a little more firmly to the colorful back plate.

[fohat]

I am a big advocate of foam, as anybody can tell from my guides, but I like it for the stability of the barrels and the tight feel that the compression ensures in the overall assembly.

Model Fs are notoriously sensitive to grounding issues and those grounding wires always need to be secure and tight. Loose grounds have caused countless headaches.

[Coeus]

Not trying to be snarky. I'm not an electrician in any way, shape, or form, am I understanding you correctly that you're saying the foam is necessary so you don't have a short?

I don't believe it serves as insulation. If it were missing it would be the square bases to the barrels that would be in contact with the barrel plate and plastic is usually an insulator unless it has been doped with something (which we assume is true of the flippers).

But I do wonder about using the keyboard without foam. I am sure I had read that this would leave the middle rows of keys a bit rattly. As some of the earlier discussion was about whether the original design was flawed I wonder if that could be corrected by making the barrel plate very slightly more concave that the base plate, i.e. the other half of the sandwich.

So maybe the foam also has a role as sound deadening. That would seem strange coming from a beam-spring with a solenoid specifically to make a noise but the general trend has been for keyboards to get quieter over time.

Given that the B key is not on one of the centre rows I am beginning to wonder is there is an issue with the spring instead. I know it is not an electrical noise problem as the feel of the key changes.

[kmnov2017]

Not trying to be snarky. I'm not an electrician in any way, shape, or form, am I understanding you correctly that you're saying the foam is necessary so you don't have a short?

....But I do wonder about using the keyboard without foam. I am sure I had read that this would leave the middle rows of keys a bit rattly. ....

I used it without the foam, makes the keyboard a bit pingy....

[hellothere]

For comparison, I used 2mm foam and it's still pingy . I did try 1mm foam and that appears to be too little, as I had some problems with keys registering. 1.5mm may be the butter zone. However, I'm not going to try that. I'm going to put it up for sale. After having all new springs and flippers and appx. 26 new barrels -- and the rest ultrasonic-ed several times -- and after a few days of testing, I've decided that I'm happier with a Model M. I know I'm not the only one. There are literally tens of us!

Anyway, the reason I bought all new springs was because keys weren't registering until I popped a key cap and tried replacing it, sometimes after several tries. There were also about a half dozen keys that I just couldn't make work until I opened the case and swapped around springs/flippers, which isn't a fun task. Then it'd be a different set of a few keys not working, etc.

[Coeus]

If so, the guy in this video doesn't use foam at all and it works fine (see also the comments).

I have finally got round to watching that video. It seemed to turn out well in the end but I am glad that was not the first Model F restoration video I watched as he makes what I would consider to be a couple of mistakes:

1. Removing the space bar before taking the sandwich apart.

2. Bending more than one of the tabs to open it - on mine it was only necessary to bend one, and it was obvious which, then slide and pull apart. I wonder what he did with the tabs during reassembly - could bending them over a bit make up for the lack of foam?

[Weezer]

You can also try things like craft paper or rubber O rings in substitute of foam. The O rings make the key feel more pingy as well as reverberative and the paper is pingy and louder than usual just like without foam however the keys are held tightly

[hellothere]

I thought about O rings as a solution, but the problem is that the small pin on the front of the barrel is something like 1mm. The O ring would probably be too thick and you wouldn't be able to get that pin through the barrel plate. Of course, you could snip the pin, but that'd allow the barrel able to rotate.

Yup. JB Weld is the way to go.

[Weezer]

I'm not sure what you mean. Granted I didn't try this on the PC/XT style barrels but the o rings I used were quite small and I can't see how they'd interfere with the pin.

Speaking of JB weld, when I got my F107, it had been used quite heavily and as the keys had started to wobble, the original operator had had the unique idea of super glueing the barrels onto the metal frame. This is always an option for those fanaticals who cannot handle one micrometer of wiggle :b

[hellothere]

Granted I didn't try this on the PC/XT style barrels but the o rings I used were quite small and I can't see how they'd interfere with the pin.

Cool. That'd save some headaches.