IBM Model F XT 83 restoration

unxmaal

19 Aug 2017, 21:44

198x IBM Model F XT 83: replaced foam, repainted top plate, modded spacebar spring. Also added a removable Teensy USB HID controller.
Image

This Model F was stored in an attic for many, many years.
Image

It still has the original cork pads.
Image

Removing keys for cleaning.
Image

@1977 Intel chip. This was the only date I was able to find on the board, or inside the case.
Image

The top plate was pretty dusty.
Image

There was plenty of corrosion.
Image

Teensy controller for testing.
Image

At this point, I found that while most keys worked, some of the flippers stuck.

I decided to take the whole thing apart and replace the foam.

As I dreaded, the foam had completely disintegrated. One side was very sticky.
Image

The other side was now mostly dust, getting everywhere, including onto the flippers, and sticking.
Image

I used an orbital sander to clean the old paint and rust off the top plate. There was still significant pitting, even after a vinegar bath.
Image

Barrel Salad: it's what's for dinner!
Image

Soaked the gross, sticky barrels in hot water and dish soap for an hour, then scrubbed each one by hand with a soft bristle brush. The salad spinner is excellent for getting the water out. I've been informed I'm no longer allowed to use that salad spinner for any edible foods.

What better color for an F top plate than bright red?
Image

First coat:
Image

After drying, the high-gloss paint showed a lot of the pits left by the corrosion.
Image

After another coat of paint, and 48hrs of drying time, it was time to work on the foam.

1/16" foam from Amazon, https://www.amazon.com/gp/product/B00TXQDYDC . It is arguably stiffer than the original foam, but it did compress adequately, and seems to do the job.

I used the top plate as a stencil.
Image


5/8" leather hole punch and a hammer to put holes in the foam. The fit was fine.
Image

The stabilizer bits poke their own holes through the foam.
Image

Completed foam:
Image

Barrels inserted:
Image

Flippers and springs inserted. The plate has to be elevated on either side, so the springs aren't damaged.

The spacebar is pure evil. It has to be inserted from underneath, then the long metal spring wire must be inserted into its stabilizer clips. One side was easy, but the other side required three hands and holding a screwdriver in my teeth.

Once the spacebar is on, the flipper won't stay put. I used a thin paint scraper to press the flipper in place, put the steel backplate on and clamped it lightly, then removed the paint scraper.
Image

First set of clamps:
Image

You can see the plate label in this picture. You'll note there's no date listed, which I find odd.

Need more clamps.
Image

Finally have enough clamps!

For future reference, screw-tight C clamps are far superior to spring clamps. You need one C clamp per top-plate clip, so at least 10, although 30 clamps might also be enough.

Here I'm using a bar clamp to exert lateral force, pushing the top plate from the right side against the bottom plate from the left. With a few squeezes of the trigger, the tongue-and-groove clips will slide together.
Image

NOTE: What isn't pictured here is the IBM Model F Restoration Rite of Passage. This is when, inevitably, the two plates fly apart, spewing springs and flippers everywhere. This will happen to you at least once.

I had to do some minor touch-up to the paint where a few clamps weren't padded properly.

After that paint dried, I replaced the caps, re-attached the Teensy, and reassembled the case.

I'm struggling getting used to the layout. I really enjoy the key weight and the very, very crisp feedback, but I hate where the ` and \ keys are located. The spacebar spring mod (which is nothing more than slightly bending its large metal spring), worked wonders on its feel.

tl;dr: spent way too much time restoring an itty keyboard when I really like full-sized boards.

gianni

20 Aug 2017, 00:46

Thank you very much, very good post and nice keyboard. I might be getting one soon.

User avatar
Daniel Beardsmore

20 Aug 2017, 00:50

At a guess, 8317 is the date code on the controller IC. The smaller chip appears to read 8324 but it's not clear from that photograph.

phughes

21 May 2019, 17:12

Great restoration. I'm currently coming to the end of my F XT 83 restoration, and I'm glad it's not just me who has gone through the sticky rotten foam, ridiculous amount of clamps, newly scratched paint and the scattering of flippers over a wide area when the plates slip.

In fact I seperated mine well over 10 times before I realised that the PCB was faulty, and not just a handful of faulty keys.I love the large clamp you used to push the two plates together. I just endud up tapping (read bashing) the two plates together using a mallet and a block of wood.

I just need to secure my Teensy down to the case and secure the cable and I'm done.


And if it stops working when the last screw it tightened, it will be used as a door stop! :evil:

Post Reply

Return to “Workshop”