Convert&Restoration project of IBM 3742 beamspring keyboard

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20 Nov 2019, 20:54

very impressive work!


20 Nov 2019, 23:07

SneakyRobb wrote:
20 Nov 2019, 20:54
very impressive work!
Thanks Robb!

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22 Nov 2019, 01:36

I just noticed the angle on your stems is flat. The stems on mine are angled. Neat.
IMG_20191119_195051.jpg (1.53 MiB) Viewed 296 times
*mine are like from this Orihalcon photo
beamspring side.jpg
beamspring side.jpg (45.01 KiB) Viewed 296 times


24 Nov 2019, 19:05

So i had all the modules cleaned. Springs were evaporusted(left small layer to prevent further rusting),o-rings, and housings were ultrasonic washed and sliders were done with cotton stick,fly plates were left untouched.

Housings in their bath:

Modules back together:

I actually ended up assembling everything back together before adjusting stems but noticed that keypresses felt loose.I proceeded to press down the stems properly and got really great results.
(spacebar rattle that is present in the vid was fixed by placing few plastic sheets between stabilizer and the barrel so they wont move around)
Everything is now assembled and its time to go back to software side again. Restoration done.

Sneaky: Thats actually quite nice catch,in didnt even think of that before you pointed it out,i wonder where this difference comes from tho?

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28 Nov 2019, 16:52


I am not sure why the stems are not as angled as other beamsprings. Perhaps due to the typing arrangement with the embedded desk keyboard they felt it not necessary to angle them. Other beamsprings are on-top of desks and much higher so it would make sense to angle the keys a bit. I am just speculating though.

As well you mentioned the PCB you are using has most but not all of the pads your original pcb has so you are missing 3 keys.

I have modified red's pcb so that the keys you are missing are present.

Because I imported a gerber into diptrace there could be slight formatting issues so, I will send the files to _red_ to look at/ask for his advice as well.

We will get those last 3 keys working!!

What i noticed about your 3 not working keys, they are missing pads. As well your enter key is overlapping, which is why you can still use it. Cool.

fix pads.JPG
fix pads.JPG (110.25 KiB) Viewed 181 times


09 Dec 2019, 21:55

Its been awhile since i have updated this thread. Since then i have managed to create a layout and get the layers working along with more testing to see if i see any odd behaviour from the kb(did few hours test run). I have now managed to get into state where everything is working as intended.

This is a good moment to appreciate members of the community that have provided me alot of information and have stayed up late hours answering my dumb questions.

Special mentions goes to kmov2017(You truly have nerves of saint what comes down answering and detailing everything,without you this kb would still be a display piece,big one to you)
Sneakyrobb(You are genuine guy who offered to help me with not even asking anything in favour,your passion is respectful)
DMA(Without your great efforts making an update to commonsense,i would be still fighting with threshold values with no clue that i cannot never get them to fully work)
JP!(You were the one who i first contacted and you told me alot of valuable information regarding this specific model. The moment you told me this thing would be convertable i was down for it)
manisteinn(Lasercutting the foam and i didnt even ask for it,genuine and hard working guy in forums,not just with this specific deed)
__red__(Making the pcb that im currectly running)

Heres a something i wanna say to you all:

I most likely do a table for it in the future along with getting last 3 keys to work.

To be continued.

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