42H0468
Variation of M2

Buckling Spring Technology
Membrane switches
RJ-11 Plug ( modular jack )

 

Got an M2 variant P/N 42H0468, a terminal keyboard with an RJ11 type plug.  

I'm not sure but it's told that the keyboard is essentially for IBM terminal 3153.  But it can be used with usual PS/2s or AT compatible computers ( or should I say  Wintel system ? ) .   All you need is LOVE for IBM Keyboard and  just to make an adapter like this  (  top page ;  Qwerters Clinic ) .  


Key Top Letters
Some keys of this board are bit different from usual M2 ( and PS/2 keyboards).
Three keys beside F12 are [Print], [Print Line], [Hold].
Upper end of Num keys are [ Num Lock] ( as usual ) then [Jump], [Send Line] and [ - ].
[End] key position  is marked as [ <- Tab ],  Page up/down  are [Clear] and [Erase EOF].
[ALT] keys beside space bar are changed to [Reset] and [Send].   See below.    


Usual M2 key top printing ( for comparison )


 Following five pictures are M2 P/N 1395300 ( anyway they are almost same ).     

 

Coil spring is same with that used in Model M, same length  and same diameter.
..... But feels very different.
Silicone grease treatment is recomended. 

In order to pull off bottom case, you have to pull out all the keys first, then release two screws at the bottom,  next you have to release 12 or 13 latches at the front side.
Turn over the bopard up side down and pull the bottom case upward.  
Every rockers with coil spring are merely pressed upward just with the bottom case together with membrane sheets and a rubber  
sheet.   

 


Model M2 variation
1395300    ; Buckling Sprig Technology.  US layout
1395706    ; same as above ,  UK  layout
73G4614   ; Rubber Dome Spring 
60G0817   ; Rubber Dome Spring, with a big face plate. code name  "Lion "...silly joke. 
60G3507   ; Buckling Spring Technology.  Labeled as M1... funny enough.

Brief information about M2 is available at 3m3718.com .  The editor of the web site says "there is an overall "cheapness" than can not help being felt when using this board.  .... snip ...... Remember, if it's not buckling spring technology, it's crap." .    
Actually it's a crap as an IBM/Lexmark product.  Buckling sound is noisy and not, err... sophisticated unlike model M.  But if you put just a small dose of silicone grease around each buckling spring,  the "cheap and crappy noise" will disappear and the board will generate mild clicky sound.     

About silicone grease;  Model M P/N 8184692  ( Japanese page ) is an example which you can see silicone grease added to every  buckling springs.  If you add grease too much, you'll loose buckling sound completely like  P/N 8184692.    


Plastic made control arms
Be careful when you pull out larger keys with a control/guide arm ( usually described as a stabilizer ) from M2 series keyboards.  Control arms are made of plastic and those keys are one-piece made with a control arm and they are easy to break.  When you pull out a space bar,  you have to release two latches of the control arm first (  circled blue in the picture below )  or the stabilizer bar will be broken easily.   In order to release latches,  push a projection on the arm which is locked in a hole of a stopper standing on a base plate toward outer direction and then lift up the arm, do  same for the another projection at the opposite end.   

You can release the latches using a thin minus driver.
I used a hand made tool to release the latches. Main purpose of the tool is for pulling out a outer case of Cherry mechanical switches mounted on a PCB directly.  


 I recommend you NOT to disassemble M2 series keyboards.  If you do, you may have some difficulties to assemble the keyboard.   I myself disassembled three M2 keyboards including this one  but every time I did I thought I'd never do it again.
......but Never say Never.  I may do it again and again because I am a MAD.


Making an adapter for 42H0468
I used an  extension phone connector  and a PS/2 cable pulled out from a non-functional mouse.
RJ-11 receptacle used in the kit has only 4 pins placed middle of six rows and the pin assignment didn't fit to the RJ-11 modular jack from the keyboard.  Then I pulled off the RJ11 receptacle and disassemble it, replaced the pins in order to meet the RJ-11 jack from the keyboard.
Checked each signal assignment of a dead mouse and soldered each cables to pins of RJ-11 receptacle.  It works just fine though some of key tops marked different from usual PS/2 keyboard.    

PIN OUT of RJ11 & PS/2 PLUG 

 

 Cool.  Isn't it ?

 

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