Model F key failure

[dramsey]

After using Mod Ms for years, the commercialization of Soarer's Converter finally prompted me to try a Mod F.

Needless to say, it was love at first type. I found two very nice units, cosmetically almost perfect, on eBay: an AT and an XT model. I prefer the AT for the larger Enter and Shift keys, although the XT version is usable if I remap the backslash key to a left shift key.

Anyway, after only a few weeks of bliss, the main "8" key on my AT failed. It was quite suddenly, in the middle of typing an email. The key feels slightly mushy now and doesn't have the crisp "snap" of the other keys; nor do its presses register. Removing the key cap shows no problem with the spring, and from what I know of the mechanics of these keyboards I'm guessing that the hammer for that key broke, and (if that is the case) that the only source for a replacement is another Mod F.

I'm competent to repair the keyboard but taking it apart looks like a pain, so I thought I`d check here and see if the assembled expertise agrees with my diagnosis.

[fohat]

You probably made the correct guess, but you will not know until you open it up.

I have never had a pivot plate break, but I can imagine how the "ear" tab could shear off.

[Redmaus]

I am assuming you have tried reseating the key? As in taking the cap off and putting it back on a few times? If that doesn't work you will most likely have to take it apart like fohat mentioned. Also check the inside of the cap and compare it to another one, to make sure it isn't just the keycap.

[dramsey]

Yes, I've taken off the key cap and replaced it; I've also tried replacing it with the "9" key cap. The insides of both caps look identical.

I'll hit the hardware store to buy some of the clamps I'll apparently need to reassemble this beast...

[Muirium]

The flippers can indeed break. Here's one from my Kishsaver:



Some potentially useful threads: Opening an AT, and Saving my Kishy. The AT's worst feature is its spacebar. Those are internally mounted and make AT's a pain to reassemble.

I've never used clamps or hammers, but I may just be doing it wrong…

[Sigmoid]

Okay I have only recently started getting into Model F's, but I've seen something very much like what you're talking about in an XT I've disassembled. It might be reassuring that the hammers are perfectly alright. (And even if you have a broken hammer, Clickykeyboards usually stocks Model F barrel and hammer assemblies.)

So the main problem is that Fs rely on a springy foam mat to keep the individual barrels pressed onto the PCB. This foam disintegrates with time, leaving the barrels without support. The vibration of use can lift them slightly off the board, causing the hammer to slip out and get stuck. The key loses its click, as the hammer can't actually "snap", and naturally, neither will the capacitive sensor register keypresses.

You likely need to disassemble the board, replace the mat, and re-seat the hammers.

[Muirium]

(And even if you have a broken hammer, Clickykeyboards usually stocks Model F barrel and hammer assemblies.)

He does, eh? Noted! I thought the only way was scavenging for ourselves.

[dramsey]

Okay I have only recently started getting into Model F's, but I've seen something very much like what you're talking about in an XT I've disassembled. It might be reassuring that the hammers are perfectly alright. (And even if you have a broken hammer, Clickykeyboards usually stocks Model F barrel and hammer assemblies.)

Doesn't look as if they do currently, sigh. But it couldn't hurt to drop him an email. I've bought stuff from him before.

So the main problem is that Fs rely on a springy foam mat to keep the individual barrels pressed onto the PCB. This foam disintegrates with time, leaving the barrels without support. The vibration of use can lift them slightly off the board, causing the hammer to slip out and get stuck. The key loses its click, as the hammer can't actually "snap", and naturally, neither will the capacitive sensor register keypresses.

You likely need to disassemble the board, replace the mat, and re-seat the hammers.

Yeah, as I poked about on the inter webs, I've seen information about this. Now where would I obtain some of this foam? Does it have cutouts for each key barrel? Surely by now some enterprising fellow has the exact foam, die-cut if necessary, for sale somewhere...

[Sigmoid]

Yeah, as I poked about on the inter webs, I've seen information about this. Now where would I obtain some of this foam? Does it have cutouts for each key barrel? Surely by now some enterprising fellow has the exact foam, die-cut if necessary, for sale somewhere...

Nowhere. You make it yourself. Get some silicone foam (it's expensive - I got two keyboards' worth of silicone foam from McMaster for $30 -, but so is the rest of a Model F), leatherworking tools, mark where the holes go, and punch them...

[XMIT]

orihalcon has some spare Model F parts, shoot him a PM. He usually includes three barrels with keyboard purchases. If he can't help you I may be able to.

[Redmaus]

Man, I also might need some barrels for the new board that wcass is making. I just used some cheap art foam for my F122 ANSI mod. But I ever get an unsaver, I might try to use something a little more high end.

[fohat]

I used some cheap art foam for my F122 ANSI mod.

Although the art foam is "cheap" I am hopeful because it is acid-free and intended for scrap-booking which is supposed to be long-term.

[XMIT]

orihalcon also sells bits of neoporene sheet for Model F rebuilds. That's what I'm planning to use for mine.

[dramsey]

I plan to disassemble the keyboard tomorrow or Thursday as time permits, then I will know what I need. Thanks for all the help!

UPDATE: I have taken the keyboard apart. Note for people who haven't done this: remove the key caps before separating the metal plates, because the hammers will not sit down far enough to let you get the bottom plate back on otherwise.

Anyway, the hammer and spring for the problematic key seem to be fine. The foam is "OK": it's not particularly springy, but it's not disintegrating all over the place either. I don't plan to replace it at this time.

The proximate cause of the problems seems to have been moisture of some sort on the PCB. There was a moderate amount of it and it looks as if it was causing the hammer for the "8" key to stick down-- at least when I removed the bottom plate of the keyboard, the hammer and spring for the 8 key came with it.

I don't know what the liquid is or was-- it wiped right off with a microfiber cloth. I've never spilled anything in the keyboard and here in very dry Reno, NV, I would have expected it to evaporate in short order if it was water. Maybe a light oil?

In any case I'm going to try reassembling now. Of course I need to make a note of the positions occupied by hammers since I need to remove all the key caps first, sigh.

[dramsey]

OK, success! After cleaning and reassembling the keyboard, all the keys work and all is well. My only remaining complaint is that the indicator LEDs don't work, but they were intermittent previously.

Here's a question: what's the function of the foam sheet, other than providing a moisture barrier and perhaps some slight stabilizing of the key barrels?

[Muirium]

Thought experiment: replace it with a harder material, like cork or even solid plastic. I bet the keyboard would feel different. And maybe sound much louder still! Your reasoning for the existence of that layer is fair enough, but the rule with keyboards is that altering things always has unintended consequences…

[Redmaus]

I thought about replacing the foam with this material on the inside of otterbox phone cases.

So spongy

otterbox-8.jpg (72.33 KiB) Viewed 5421 times

Anybody know where I could get this material thicker and larger?

[fohat]

The foam layer is a "bedding" layer for the barrels. With the alignment tabs, and the fact that most of them sit shoulder-to-shoulder, it may there mostly for electrical and sound insulation.

After compression, the thicker that layer is, the harder it will be to get the plates back together. My guess is that unless you can compress it down to about 1mm (or less) you will have a hard time wrestling the rest of the assembly into place.

[dramsey]

I suppose if I were brave, I could try assembling a keyboard with no foam layer. Perhaps that would make the barrels "rattley". On the other hand, perhaps a new silicone foam layer would be nicer. Is there a standard tool people use to create the barrel holes in this foam? Trying to cut them out with an Exacto™ knife would seem to be very tedious.

[0100010]

Yes, cutting the foam with an exacto / razor blade is very time consuming (I know because I went through three sets of different types and thicknesses of foam for my F107 before I was satisfied). Others state it is much easier to cut the holes out with a leather punch.

The foam I settled on was 1/4" automotive headliner foam. Was super cheap, extremely compressible and resulted in the best key feel for me. I did also try a couple thicknesses of art foam - but wasn't satisfied with it. Wasn't willing to wait to order anything fancier either, like silicone.

[XMIT]

0100010 did you prefer the headliner foam over neoprene? It seems to me neoprene would be ideal for this application.

[Sigmoid]

Silicone foam (not a solid silicone rubber sheet - I've read some people had a hard time with that understandably) is nice and soft, flame retardant, highly inert and non-agressive... However, from my recent experience, it has a huge drawback: static electicity. This thing is electric. So much so that I ordered some topical dissipative to coat it with before assembling the keyboard.

And I don't think I'd even dream of trying to use an xacto knife to cut circular holes in it... You can get a cheap Chinese leather punch set for $10.

[0100010]

0100010 did you prefer the headliner foam over neoprene? It seems to me neoprene would be ideal for this application.

Never tried neoprene. I am extremely satisfied with the headliner foam.

[dramsey]

The neoprene foam I see online (i.e. Amazon) is closed-cell stuff, which means it will take more effort to compress. Has anyone actually used it? I wonder if the effort required to press down 104 (or however many) key barrels against even a thin layer of closed-cell foam would make reassembly too difficult.

The degraded (yet not disintegrating) foam in my AT-Mod F is much thinner than 1/4".

[Redmaus]

Is the material in the otterbox case neoprene?

[dramsey]

And I don't think I'd even dream of trying to use an xacto knife to cut circular holes in it... You can get a cheap Chinese leather punch set for $10.

Any Amazon links? The holes look like about 1/2", and none of the leather punches I see are anywhere near that large...

[Sigmoid]

And I don't think I'd even dream of trying to use an xacto knife to cut circular holes in it... You can get a cheap Chinese leather punch set for $10.

Any Amazon links? The holes look like about 1/2", and none of the leather punches I see are anywhere near that large...

7/16".
http://www.amazon.com/TEKTON-6587-Hollo ... B000NPUKX4

[Redmaus]

I have a gromett kit that costs like 11$ from home depot and it works perfectly.

[Muirium]

Got a link? I may swing by while I'm still in Cali.

[0100010]

Maybe? http://www.homedepot.com/p/General-Tool ... /100200416