IBM Model F XT space bar issue


16 Oct 2018, 10:32

Hi wonderful people of deskthority!

I have finally received my converter from tinkerboy yesterday. I was ready to try out the Model F and to my surprise all keys have registered and were fully functional, except one, the space bar.

When the keyboard came I had to recognize that the metal plate sat completely loose inside its case, were the bending ear did not hold together at least anything. So I have opened up the case, pulled off all keycaps except the space bar, because I was afraid of all the scary descriptions regarding the Model F space bar. So now in this state the springs were free to fall down inside the barrels while the plate is upside down. I did not care for the space bar, maybe this was wrong, but I thought as long as I won't pull of the space bar key I can't do anything wrong. I have put the metal plate back, made it it tight by using the metal clamps and now all keys show a keycode and register except the space bar.

What did I make wrong? Do I have to clean the matrix, but how? Is there any step by step solution for reinserting the space bar? I can open the keyboard once again and make some pictures in case this might help you to give me some necessary advice.

Thank you very much in advance and any kind of help is really appreciated.


16 Oct 2018, 10:47

Hi, you were right to not pull off the space bar without first removing the back plate as the space bar is held in place with a leaf spring between the barrel plate and the back plate. because the space bar remains in place when assembling the spring inside the switch is going to be under compression due to the cap therefore will not want to stay in position without some way of holding the flipper in place whilst the plates are secured together. As you can't remove the space bar to reseat the flipper, you would need to disassemble the board again and this time use something thin and stiff like a smooth credit card or small metal ruler to hold the space bar flipper in place whilst the two plates are being clamped together. As long as the plates are together then you can remove the ruler/card to avoid damage when pressing the back plate into the tabs.


16 Oct 2018, 12:04

^^ Ok, thank you very much for your answer. I will try to do the procedure the way you have described it with the help of a metal ruler. I hope I have not already destroyed the matrix, for instance the flipper scratched the surface of the matrix. :cry:

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16 Oct 2018, 13:58

Don’t think you should be in trouble. Those model F “pad cards” as IBM called them (the flexible matrix PCB) are pretty tough and well masked. The foam is the weak spot.


18 Oct 2018, 12:50

I have got one more question: How am I allowed to clean the the flexible matrix PCB and the flippers? May I use isopropyl for cleaning or might this cause any damage? What kind of rag should I use?


18 Oct 2018, 13:41

Most of the PCB is covered throughout with solder mask. Any kind of rag should do as long as it's not steel wool.

If you want to use any solvent which you haven't used before then try rubbing it just on one corner of the PCB, then leave it sitting for 15 minutes after it was first made wet. If it didn't become sticky after that then your solvent should be fine.


19 Oct 2018, 10:00

I am really grateful for all the help and my Model F XT is finally working! I can't believe it and I am actually typing on it. It feels so great!

The advice with the metal ruler did the job and it worked on the first try. Now I am ready to play around with different layouts.


19 Oct 2018, 10:41

Glad that i could help, and you will have a solid board for years to come :)

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