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PS/2 Model 'M' - 1995 Lexmark -> rubber pad and photos

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ultra24:
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I have seen a post or two where the original mat has been replaced by a sheet of thin silicone, resulting in a perfectly working keyboard where replacing the original mat had failed.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

fohat.digs:
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.

ultra24:
Hello:

--- Quote from: fohat.digs on Wed, 16 June 2021, 11:31:41 ---... conflating components of the Model M and the Model F.

--- End quote ---

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

ultra24:
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

ultra24:
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

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