Author Topic: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos  (Read 1045 times)

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Offline ultra24

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PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« on: Wed, 16 June 2021, 10:50:47 »
Hello:

I'm currently awaiting for delivery (today!) of my newly acquired 1995 Lexmark PS/2 Model M.
Like I mentioned in another post, it is an attached flat cable-PS/2 model albeit with a missing plug. (p/n 82G2384)

In the process of cleaning/inspection I may have to do a screw (not bolt/nut) mod and will inevitably come across the rubber/plastic mat between the plates.

I have seen a post or two where the original mat has been replaced by a sheet of thin silicone, resulting in a perfectly working keyboard where replacing the original mat had failed.

But I have not seen any data with respect to the silicone sheet's thickness.

I think one of the 'model M' repairers/purveyors offers them in ready cut/made form, but I have a large sheet of 1.0mm silicone mat I can probably use.

Does anyone here have any idea as to what thickness the new silicone mat should be? 

Thanks in advance.

U24
« Last Edit: Wed, 16 June 2021, 13:58:08 by ultra24 »

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad
« Reply #1 on: Wed, 16 June 2021, 11:31:41 »
You are conflating components of the Model M and the Model F.

Your model M will have a black rubber mat with very small holes for the "rivets" to go through on their way to the back plate where they are melted down into a "mushroom" shape. Some years ago Unicomp replaced the black rubber with a very thin white latex sheet. These are superior, in my opinion, but unnecessary, and can be installed only if you take the internal plates apart. Unicomp will sell you one for about $10.

Model F keyboards have a foam mat that fulfills a completely different function. These break down over time but the Model M mats do not.
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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad
« Reply #2 on: Wed, 16 June 2021, 13:57:33 »
Hello:
... conflating components of the Model M and the Model F.

Hmm ...
This is my first Model M and I have evidently confused things.

I had understood that there was a rubber something in between the Model M plates, held in place by the plastic rivets which hold the plates together and that, if the are broken, have to be replaced with either of two options. ie: bolt/nuts or screws.

My confusion is because I incorrectly assumed all IBM keyboards (F and M) shared the same matting and thus suffered the same decay.
Makes sense that it would degrade after 26 years.

Thank you for clearing that up for me. 

I'll be posting on this thread some photos of my board as well as some questions.

Thank you for your input.

Best,

U24

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #3 on: Wed, 16 June 2021, 14:22:06 »
Hello:

I'll continue on this thread (unless admin decides otherwise).

This is a US Lexmark Model M - 82G2384 I made an offer for and later purchased around a month ago.
Covid and all the mess we're currently in conspired against my having it sooner. 



It is remarkably clean and save for the cable and bashed up PS/2 connector, in really great shape.
The flat cable's rubber sheeting was totally disintegrated.







And the rivets are all in place, not one is popped.



Hopefully this will last.

There was a sticker on the exposed plate:


 
And the (assembly?) date written inside the top cover by someone at Lexmark, pity it wasn't also signed:



The Chinese made controller board and the eeprom seem the be (?) the same as others I have seen:







All keys and keycaps came off without much ado.
They are now bathing in my ultrasound with some red degreaser concentrate I got as a gift when a local BKing closed.

I'll follow up with another post with a question regarding the Enter key and how it is mounted in this particular keyboard.
Looks strange to me but maybe I am mistaken.


Best,

U24
« Last Edit: Wed, 16 June 2021, 14:57:59 by ultra24 »

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #4 on: Wed, 16 June 2021, 15:19:15 »
Hello:

This particular Model M keyboard goes by IBM Part #82G2384 and FRU 82G2394 and it is the 102 key Latin American Spanish ISO version, so it has the long Enter key.

When inspecting the keyboard on delivery, I saw that all the keys travelled and clicked as expected, save for the Enter key which was stuck.
I did not pay much attention to that and thought it ws just some dirt/grime. 
 
But when I started to take it apart I came across something I have not seen in any posts:



These two thingies apparently are responsible for the Enter key coming back up once depressed:



Without them in place, the key will stay down.

Not only that: although I have to check again once everything has gone through the first phase of cleaning everything up, I cannot hear the familiar click when I push the Enter key down.

This would seem to be the first problem I am encountering with my Model M.

Q: Anyone seen this before?
ie: is this standard OEM, a factory patch or a previous owner's attempt at repairing a bad enter key mechanism?

Thanks in advance.

Best,

U24
« Last Edit: Wed, 16 June 2021, 15:26:37 by ultra24 »

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #5 on: Wed, 16 June 2021, 16:03:03 »

ISO version, so it has the long Enter key.


Usually when someone says "the long Enter key" they are referring to the horizontal rectangular one, commonly called "ANSI" Enter.

I have never seen anything quite like that. The stabilizer inserts (the hollow tube-like parts that drop into the barrels) come in 2 types: the ones for horizontal keys have the holes centered, while the ones for vertical keys are off-center.

Attached is a photo that I pulled up off the web showing how they are oriented. From my experience I would say that someone put the top insert for Enter in upside-down and it was binding. But if the tall 2x keys on the numpad work properly, I don't know what to say because I have never seen any like that.
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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #6 on: Wed, 16 June 2021, 16:33:08 »
Hello:
... "the long Enter key" ...
... referring to the horizontal rectangular one ...
I see.
Thanks again.

My guess is that this one is referred to as the short ISO key?

... never seen anything quite like that.
... stabilizer inserts (the hollow tube-like parts that drop into the barrels) come in 2 types ...
... for horizontal keys have the holes centered
... for vertical keys are off-center.

Here's a couple of photos of what the key stems look like:





... photo that I pulled up off the web showing how they are oriented.
I'll see if I can compare anything.

... someone put the top insert for Enter in upside-down ...
The gray off centre insert in the barrel?

But if the tall 2x keys on the numpad work properly ...
Apparently it does (heard it click as expected) and it seems to be the same arrangement.
ie: gray off centre insert in the barrel

And the corresponding key has the same morphology ...



... but does not have a pair of rubber thingies to send it back up. The key comes up by force of the spring.

Maybe there's some cleaning/lubrication needed?

Edit:

Was able to remove the insert and put it back rotated 180.
Did not go well, the key gets stuck.

Took it out and gave it a throrough cleaning before putting it back in again as it was before.
Success!

The key now works as intended without having to put the rubber thinguies in place again.
But I cannot hear it click.

No matter, we're half way there.
Being one of the most used (if not the most used key) on a keyboard, maybe it's a question of having a chat with the spring.

Now to see about cleraning up the case.
Much to my chagrin, the yellowing may just be is plastic yellowing and not nicotine.

I don't want to scrub it too much as it will end up taking a shine.
Corega tabs maybe?

Thanks for your input.

U24
« Last Edit: Wed, 16 June 2021, 16:59:37 by ultra24 »

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #7 on: Wed, 16 June 2021, 18:01:28 »
Never trust color. I have inserts in many colors, but Unicomp sell white ones that are horizontal and black ones that are vertical. You have an ISO standard Enter key.

It can take many tries to get a key stem seated properly. If it doesn't work right of, most of us stand the keyboard up (on the space bar side) to make the spring flop down, and try inserting it that way, then lean it the other way (one the function key side) to get the spring to flop back) and try it that way. Eventually it will find its way into place.

If you look into the key stem you will see a tiny dimple that the top of the spring needs to seat onto. When that happens, it will be seated correctly and will click properly.

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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #8 on: Wed, 16 June 2021, 20:51:05 »
Hello:
Never trust color ...
As an architect by trade, I don't.
I only trust what I see and how I see it.
I was just making a reference to the others. 8^)

... have inserts in many colors ...
Four or five of the keys in this keyboard are of a different coloured plastic.
But morphologically, they seem to be identical.

... can take many tries to get a key stem seated properly.
So I have read.

My problem is not so much that it won't click although it is rather dissapointing if it cannot be fixed.
My problem will be if the Enter key does not register.

I have to go out for a PS/2 -> USB conversor tomorrow, so I won't know how everything is registering till I get it properly wired.
I found a sample with the proper chip (13ba:0018 PCP-BCG4209) so it is just a question of hard-wiring it inside the case.

That particular key (ie: Enter), with the rubber thinguies added on must have been banged to death.
Maybe the flapper has moved, is not properly seated or it's damaged?
I've seen you can buy sets of 10 for around US$1.00 ea., so it won't be too much of a problem, just a question of time and money.

As a last resort, I have the screw mod, which I was hoping to avoid.
Particularly since all the rivets are in one piece.

... most of us stand the keyboard up ...
... then lean it the other way ...
... and try it that way.
Eventually it will find its way into place.

I've already tried that.
Will try again, of course.

I also took out and straightered the spring which was bent, to no avail.
And switched springs with one of the direction keys but it did not work.

As a result, I now have two keys that do not click. LoL!!!

... look into the key stem you will see a tiny dimple ...
Yes, I already figured that one out.

But I'll get it done, sooner or later.
First I need to finish up the clean-up.

The keys and keycaps are now as NIB.
Great invention, the ultrasound cleaner.

But the barrel board is rather hard to clean when you cannot put it in warm water and degreaser.
And the q-tip method gets old in a short while.

Then there's issue of the slightly yellowed case, I'd like to get it a bit cleaner.

Any suggestions?

Thanks for your input.

Best,

U24

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #9 on: Wed, 16 June 2021, 22:33:17 »

can take many tries to get a key stem seated properly.

That particular key (ie: Enter), with the rubber thinguies added on must have been banged to death.

Maybe the flapper has moved,


And the q-tip method gets old in a short while.


The easy test is to pull out a random single key stem and use it to test the active working contact you are interested in.

I suppose that it would be possible for a Model M pivot plate to move but that is much more common on the Model F.

Without taking it all apart all I can recommend are alcohol, paper towels, and Q-tips.
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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #10 on: Thu, 17 June 2021, 07:05:32 »
Hello:
... pull out a random single key stem and use it to test the active working contact ...
That's what I did.
All keys clicked with the sole exception of Enter.
Like I mentioned earlier, exchanging the Enter spring with another did not work and the resut was another key that does not click.

But the (now non-working) spring is correctly installed.
It worked before so why not now?

... would be possible for a Model M pivot plate to move ...
... much more common on the Model F.
Good to know.

... all I can recommend are alcohol, paper towels, and Q-tips.
Hmm ...
That's where I'm at now.  8^/
Maybe a different brush/foam tips?

I'll post back when I get the converter wired in.

Thanks a lot for your input.

Best,

U24

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #11 on: Thu, 17 June 2021, 19:41:41 »
Hello:
.. when I get the converter wired in.

Got the converted wired in.
Thought it was much better than using the alternative option of a Teensy board/clone + firmware.
No need (for me) to have all that in a keyboard.

We're almost there:



Recovered a very good quality USB cable whcih I salvaged from an old Wyse rubber dome keyboard



Still have not solved the Enter key issue but the Up direction key is back to it's previaous state, it now clicks as expected.

But I have come up on a new problem:



This piece was in perfect shape when I removed it.
Must have been cracked and shuffling it around in the ultrasound was the last straw.

It is a problem that I have experienced in quite a few keyboards, very annoying.
Cannot understand the reasoning behind the crappy and fragile little snap to hold the wire in place.
I always had to get a part from another keyboard and was not too much of a problem, not the same situation.

Any idea on how to fix it?
Dental light-activated acrylics come to mind, but it's a very expensive material.

Thanks in advance.

Best,

U24
« Last Edit: Thu, 17 June 2021, 21:04:38 by ultra24 »

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #12 on: Thu, 17 June 2021, 21:43:03 »
If you are in the US it is a simple matter to order one from Unicomp or clickykeyboards.

Otherwise you could fabricate a tiny arm and epoxy it in place, or create a mass of epoxy and drill it out.

If you can find a tiny washer of the right size inner hole you might be able to epoxy it in. Tricky thing when it gets that small.

These are all just suggestions that I have never tried. I have only broken one like that, and I had a spare lying around.
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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #13 on: Fri, 18 June 2021, 06:16:31 »
Hello:
If you are in the US ...
Not the case.
It would be a last resort, shipping+taxes will make the piece more expensive than this keyboard.
I'll ask around if anyone of the sellers on the local ebay type site have this piece.

I remember seeing years ago a keyboard with a space bar that had a spring coil where the empty barrel is.
Any other IBM keyboards use a different (ie: not a wire stabiliser) solution for the spacebar?

... fabricate a tiny arm and epoxy it in place ...
That's the solution I had thought to use the light-activated dental acrylic with.

... tiny washer of the right size inner hole you might be able to epoxy it in. Tricky thing when it gets that small.
I could eventually make a piece from thin sheet SS I have laying around and epoxy it in place.

Thanks for your input.

Best,

U24

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #14 on: Fri, 18 June 2021, 07:32:34 »
Hello:
...  piece from thin sheet SS I have laying around ...
Done, much easier than I thought.
Hopefully it will hold.

Used a strip of thin plated sheet tin I had around and bent it to a shape that would replay the action of the broken piece.
Glued it in with cyanoacrylate, hopefully it will be a durable solution.

If the other side breaks, there is no room for this type of solution.
Having made them just 50/60% wider would have made these snaps/holders much more resistant
Such a well built/designed keyboard with such a sloppy solution for the stabiliser, a real pity.

      

 270862-2     

Still have to deal with the Enter not working ...

Best,

U24

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #15 on: Fri, 18 June 2021, 08:13:49 »
That looks like a good repair, and it could be "tuned" by bending the metal slightly.

Although ancient IBM gear can be dismantled and serviced, my guess is that their assumption was that 99% of it would never be re-opened during its 5-year life cycle. Damage like yours would likely only result from tinkering. And there was a limitless supply of spare space bars.
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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #16 on: Fri, 18 June 2021, 08:36:09 »
Hello:
... looks like a good repair ...
Thank you.

... could be "tuned" by bending the metal slightly.
Yes, that's one reason I went with the metallic solution.
It was at hand and my experience with epoxys did not augur much success given the size of the piece to be reconstructed.

... their assumption was that 99% of it would never be re-opened ...
Yes, that would a reason.

But my guess is that there was probably a beancounter hanging around.
And we all know how that usually goes ...

Thanks for your input.

Best,

U24

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #17 on: Fri, 18 June 2021, 08:59:34 »

my experience with epoxys did not augur much success


Here in the US we have a popular epoxy called "JB Weld" that is excellent. The classic original type was formulated for the automotive industry and has quite a bit of iron in it for strength and heat
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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #18 on: Fri, 18 June 2021, 09:15:56 »
Hello:
... epoxy called "JB Weld" that is excellent.
... formulated for the automotive industry and has quite a bit of iron in it ...
Yes, I know about it but have never used it.
Thanks for the heads up.

I have been using epoxys and cianos for the longest while.
Cianos I combine with very fine acrylic powder, applied to seams after joining the pieces to strengthen them.

I reinforce epoxys with the produce of my bench grinder or filing operations.
These activities  can get me quite a bit of metal powder, from plain/stainless steel to aluminium and even copper.
The produce is then passed through a thin metal sieve and stored in a small plastic jar.

But the problem in this specific case is the tiny size of the broken tab.
I don't think ant epoxy would do.

Thanks for your input.

Best,

U24

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #19 on: Fri, 18 June 2021, 09:30:06 »

the tiny size of the broken tab.


I was not suggesting that you reproduce that single "ear" but instead build up a larger blob (a few mm in each dimension?) and then drill a tunnel through it.

You would need to remember which end it was the next time you pull it up from the keyboard so that you could be careful in that area. Because the wire could not easily pop out transverse to the space bar but would have to be inserted and removed longitudinally.
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Offline Snowdog993

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #20 on: Fri, 18 June 2021, 10:41:04 »
I have been reading this dialogue and wondering why not just get a new spacebar from Unicomp?
A pearl spacebar is what? $3.00?
Oh, never mind.

Offline Snowdog993

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #21 on: Fri, 18 June 2021, 10:54:11 »
Oh! Another thing I noticed was the ISO enter key having some sort of bushing pushing up the key? That is not by any way a part that is for the keyboard at all.
What I believe is the problem is the spring itself is bent out of whack by forcing the key down on the barrel.
Check that spring. Make sure it is like the others that do buckle.
If the spring is fine, be sure that it is not twisted into the key, but rather seated properly. If the stem on the stabilizing part is too long, you can file off just a tiny amount of the long plastic stab on the key itself, preventing it from bottoming out.
I will just say this is a very simple fix.
Hope it helps!

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #22 on: Fri, 18 June 2021, 15:26:33 »
Hello:
... not suggesting that you reproduce that single "ear" ...
Of course not, didn't think that you did.
Still, my experience with reproducing small parts in epoxy has not been good although it's great for filling in.

Done much better with acrylics but the right ones are hard to come by in small batches.
And the light activated ones used for dental work are quite expensive.

Thanks for your input.

Best,

U24

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #23 on: Fri, 18 June 2021, 15:29:41 »
Hello:
... wondering why not just get a new spacebar from Unicomp?
For me it's about minimum shipping fees, import taxes, etc.
Your $3.00 can turn into $30.00 is the bat of an eye.

Thanks for your input.

Best,

U24

Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #24 on: Fri, 18 June 2021, 16:01:23 »
Hello:
... ISO enter key having some sort of bushing ...
Fortunately, I solved that already.

Some previous owner long ago had a problem with that key sticking and figured that could help.
Not a bad idea and maybe it did, but for just a while.

I have since managed to get the key to register but not to click as expected.
Once I made sure it registered by just pushing the spring, I took it out and stretched it a bit while I had it threaded on a 2.0mm steel rod.
Like what you see in a small electronics type screwdriver, which are very strout and prefectly straight:



But now it is a bit too stiff, so I'll have to attend to that.

... spring itself is bent out of whack ...
Yes, I thought so too, mentioned that earlier in the thread.

Check that spring. Make sure it is like the others ...
Yes, earlier on in the thread I exchanged that spring with another one.
No cigar and once in it's original place, the substitute did not register for a while.
Now it's doing well but the click  became noticeably softer.

I have come to the conclusion that these springs acquire a working position due to their 'buckling' always in the same direction.
Five or six years doing the same 'buckle' has to have some sort of memory effect.

Then one day you take it out to clean everything up and put it back in place when you are done.
Back in place but maybe in a position that could be up to 180 opposite the position it is used to work in.
Chances are that it will not click and maybe not even register.   

... be sure that it is not twisted into the key, but rather seated properly.
... stabilizing part is too long, you can file off just a tiny amount ...
I'll look into that.

Thanks a lot for your input.

Best,

U24

Offline fohat.digs

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #25 on: Fri, 18 June 2021, 16:37:36 »

springs acquire a working position due to their 'buckling' always in the same direction.

years doing the same 'buckle' has to have some sort of memory effect.


When I read this, I thought "reasonable thought experiment, but no" since I have never experienced what you described.

Having rebuilt dozens of Ms and Fs and typing this on a 1984 I do feel that I have considerable empirical experience with buckling springs, but thinking back I realize that I never remove springs from their pivot plates. As in, maybe on 2 or 3 occasions out of thousands of spring settings. Monkeying around with springs is something that I scrupulously avoid doing and fortunately I have plenty of spares, but I take the keyboard apart to the install replacements. I have seen the "chopsticks of death" but never tried it myself.

If a spring is bent or permanently deformed in any way, I assume that it is history.

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Offline ultra24

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #26 on: Fri, 18 June 2021, 17:45:23 »
Hello:
... I thought "reasonable thought experiment, but no" ...
... never experienced what you described.
Maybe not, but memory effect in springs exist.

Basically it is the reason why eg: in cars, trucks, lever espresso machines, etc. springs* eventually have to be replaced.
And if taken out for cleaning, they have to be put in as they were.   (* coiled springs which are in any way compresed or extended)

... realize that I never remove springs ...
That's the very motive you have not seen it.
It arises when the spring is not in its original position eg: the one it has always been in. 

... something that I scrupulously avoid doing ...
From what I have seen, a good decision.  8^)

I have finally fixed the spring problem and, uncannily enough, actually recovered the click for the Enter key.

I used an alternate chopstick method I picked up while looking for data on how to get these things done.
Very ingenious but not my idea so no credit due, unfortunately I can't recall the site.

It does involve a stick but I use a plastic tube that came with one of my WD40 cans.
It also involves a sheath, another plastic tube but from a Windex type sprayer into which the spring just slides in.



The outer tube has a containing efect on the spring as it is rotated anti-clockwise while lightly pushed downwards.   
ie: it keeps the spring straight and evenly unwound outwards and the rotating force going forward and not dispersing outward, so to speak.
Can't recall enough from the clases at the uni to explain it better but take my word, that's what happens.

You put the outer tube on the post.
The slide the inner tube with the spring on the tip into the outer tube.
The rest is as always.

The result is a spring that has been firmly screwed into the post, all the way to the bottom, which I think is critical for it to work properly.

Thanks for your input.

Best,

U24

Offline Snowdog993

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Re: PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos
« Reply #27 on: Fri, 18 June 2021, 21:20:00 »
Thanks for your input.
U24
You are most welcome.