IBM M2 restoration log - No one left behind!

j0d1 · 29 Mar 2018, 16:54

In the following days, I will restore this IBM Model M2, which I acquired for 50$CAD shipped (~38.75$USD).
This keyboard has a bad reputation but frankly, I like typing on it and the build quality is not as poor as I read.
However this keyboard is not working and I do not accept non-working keyboards in my collection!

Front and back shots

: 01.before.front.jpg (2.18 MiB) Viewed 6770 times

: 02.before.back.jpg (1.96 MiB) Viewed 6770 times

The keyboard was dirty as hell.
I will spare you the graphic content.
I removed and cleaned every component of this keyboard.
There are plenty of other tutorials on this so here is a simple summary of what I did:

Clean the PCB and matrices with rubbing alcohol (70% ethanol) and cotton swabs.
Clean the case and keys with hot soapy water and a toothbrush.
Clean the black spots on the case with baking soda, paper towel and a little bit of water. I put this in bold because it really does miracles and it's more effective than rubbing alcohol.

Things to repair

Two springs are stretched

: 04.before.broken_springs.jpg (1.84 MiB) Viewed 6770 times

Wires of the cable are exposed

: 05.before.broken_cable.jpg (1.24 MiB) Viewed 6770 times

The stabilizer on the Shift key is broken

: 06.before.broken_stabilizer.jpg (703.77 KiB) Viewed 6770 times

Some broken case pins that I found under the keys

: 07.before.broken_pins.jpg (1.82 MiB) Viewed 6770 times

And of course, the capacitors on the PCB need to be replaced (C1 and C3)

: 09.pcb.jpg (3.04 MiB) Viewed 6770 times

Current progress

Cleaned the bottom case

: 10.case.bottom.jpg (3.96 MiB) Viewed 6770 times

Cleaned and put back the thin metallic sheet at the bottom of the case

: 11.case.thin_metalic_sheet.jpg (3.79 MiB) Viewed 6770 times

Cleaned and put back the first matrix layer (also scanned and added to the wiki)

: 12.matrix_layer_1.jpg (3.93 MiB) Viewed 6770 times

Cleaned and put back the second matrix layer (also scanned and added to the wiki)

: 13.matrix_layer_2.jpg (3.96 MiB) Viewed 6770 times

Next steps

I will attack each issue individually, starting with the replacement of the capacitors on the PCB. If you have any ideas / suggestions / etc. for each issue, please let me know.

green-squid · 29 Mar 2018, 16:58

Can't wait for more progress!

Ir0n · 29 Mar 2018, 17:33

Jeez with that many broken tabs you're gonna have to do a weird bolt mod.
At least the holes are already there for it kind of.. Lol

I was thinking of doing a bolt mod to mine.. those tabs are trash.

j0d1 · 29 Mar 2018, 18:23

Yeah they are really fragile.
There are a total of 13 on the keyboard and 5 of those are broken.

: 07.before.broken_pins.2.jpg (4.34 MiB) Viewed 6729 times

The top case was still firmly attached to the bottom case so I'm wondering if I should replace them or not.
If I do, some kind of bolt mod is a better idea than trying to put back the original tabs (with crazy glue, hot glue, melting the plastic around, ...)
The holes in the bottom case are not aligned with the ones in the top case but this can be fixed.

Obviously I am not touching the broken tab in the middle of the keyboard because it is right above the precious label.

DustGod · 29 Mar 2018, 21:00

What a mission! Good luck for this restoration!

Blaise170 · 29 Mar 2018, 21:04

j0d1 wrote: ↑ This keyboard has a bad reputation but frankly, I like typing on it and the build quality is not as poor as I read.

Agreed.

balotz · 29 Mar 2018, 21:11

j0d1 wrote: ↑Yeah they are really fragile.
There are a total of 13 on the keyboard and 5 of those are broken.

07.before.broken_pins.2.jpg
The top case was still firmly attached to the bottom case so I'm wondering if I should replace them or not.
If I do, some kind of bolt mod is a better idea than trying to put back the original tabs (with crazy glue, hot glue, melting the plastic around, ...)
The holes in the bottom case are not aligned with the ones in the top case but this can be fixed.

Obviously I am not touching the broken tab in the middle of the keyboard because it is right above the precious label.

I have restored three of these boards, replacing capacitors on all of them. Strangely I've not seen a broken tab, except for the ones holding the PCB.

j0d1 · 29 Mar 2018, 21:44

I received the keyboard with all the broken tabs under the keycaps so it looks like it happened during shipping.
I assume the previous owner would have removed the broken tabs if he opened the case before selling it to me.
That mystery will never be resolved.

For the PCB tabs, I managed to break one while removing the PCB, oh well

Blaise170 · 29 Mar 2018, 21:50

I once bought a Greek M2 and tried opening it and I think I broke every tab in it, assuming the tabs weren't already broken. The tabs in M2's are so fragile that you could probably break them just by typing too hard. Either way, I think it was a pleasant typing experience and I actually prefer them to regular M's.

Darkshado · 30 Mar 2018, 06:28

So that makes two Montreal DT posters with M2s. Haven't done anything with mine yet so your photos should come in handy. It does seem in a better shape, though I don't have too much hope wrt the capacitors. Mine is in the French Canadian layout and I got it for 10$CAD, picked up in a village past Drummondville on my way to Quebec City.

j0d1 · 31 Mar 2018, 05:22

10$CAD for an M2 is a bargain!

Fixing the capacitors

I replaced the two faulty capacitors.

C1 requires a 47uF 16v capacitor.
C3 requires a 2.2uF 50v capacitor.

Removed the old capacitors

: 15.pcb.removed_capacitors.jpg (1.35 MiB) Viewed 6638 times

I simply pulled the capacitors with pliers while applying heat to the pads and they easily came off.
The polarity of each capacitor is clearly indicated on the PCB (the + sign for the anode) so it difficult to make a mistake when installing the new ones.

Soldered the new capacitors

: 16.pcb.replaced_capacitors.jpg (1.59 MiB) Viewed 6638 times

That's not the best soldering job but it will do.
I plugged the keyboard and pressed on the matrix membranes and it works!

Next steps

Tomorrow I will fix the cable, which seems like a very easy job.

j0d1 · 31 Mar 2018, 18:14

Fixing the cable

How it looks like before the fix

: 17.cable.issue.jpg (1.23 MiB) Viewed 6612 times

Close up on the issues

: 18.cable.issue.2.jpg (1.85 MiB) Viewed 6612 times

As you can see:

The ground cable is cut in half.
Part of the cable sleeve is stuck in the holder.

Cleaning the holder... oops.

: 19.cable.cleaned_holder.jpg (2.23 MiB) Viewed 6612 times

I made a cut in the holder (is it the proper name of this thing by the way?) because for a moment I thought the holder was simply not large enough to accomodate the cable sleeve.

That's when I realized a chunk of the cable sleeve was simply stuck inside it, so I removed it with an exacto.

Cable fixed!

: 20.cable.shrink_tube_and_hot_glue.jpg (2.72 MiB) Viewed 6612 times

I reattached the ground cable and added a shrinking tube to securize it.
I hot glued the holder onto the cable sleeve so it is more resistant to a pull on the cable.

Cable installed on the PCB

: 21.cable.installed.jpg (1.77 MiB) Viewed 6612 times

Next steps

Fixing the stabilizer on the Shift key.

fohat · 31 Mar 2018, 18:22

Good fix. I have always wondered about the electrical properties of hot glue.

The piece you asked about is a grommet.

Daniel Beardsmore · 31 Mar 2018, 18:25

I just noticed something — that PCB was made by Wong's Electronics of Hong Kong.

j0d1 · 31 Mar 2018, 19:14

fohat wrote:Good fix. I have always wondered about the electrical properties of hot glue.

From what I read, it depends on the composition of the hot glue but in most cases, it is an insulator.

fohat wrote:The piece you asked about is a grommet.

Thank you!

Ir0n · 31 Mar 2018, 20:22

Huh... You used through hole caps.. I bet that is way more easy to solder than SMD ones.

Looks good so far.

Darkshado · 02 Apr 2018, 01:22

So I took care of mine this weekend, typing this post on it.

: IBM 1395705 French Canadian Model M2; 2018-04-01 16.32.31.jpg (1.69 MiB) Viewed 6022 times

Looks like the capacitors on mine are still good, so I left them as is.

: PCB; 2018-04-01 14.44.04.jpg (1013.93 KiB) Viewed 6022 times

There was some corrosion on the membrane traces, especially near the contacts for the controller PCB.

: Membrane corrosion. Gentle rubbing with a pencil eraser got rid of that.; 2018-03-31 00.40.15.jpg (3.69 MiB) Viewed 6022 times

Reassembly is best done with something to raise the inverted top half of the case, e.g. these two yogurt containers:

: Raised M2 top shell with flippers inserted. Rolled up small size sticky notes identify barrels to be left empty.; 2018-04-01 14.50.25.jpg (2.05 MiB) Viewed 6022 times

Set the mat on top, hold the membrane on the "left" end (the one with Escape, opposite the controller PCB), lower it onto the top shell and snap into place:

: Mat laid on top half shell.; 2018-04-01 14.51.56.jpg (1.36 MiB) Viewed 6022 times

Tips:

Begin keycap installation with the stabilized keys. On ISO boards, place Enter just before moving onto the 1u keys.
I had to use a cotton swap to pull the mat outwards on the numpad + and Enter keys before they clicked correctly.
Broke a plastic stabilizer leg on the Numpad + but am under the impression the barrel inserts alone are enough to stabilise the keys.

I have broken off a retaining tab during dissassembly...

: Broken tab; 2018-04-01 15.42.35.jpg (1.92 MiB) Viewed 6022 times

But came up with the "zip tie" mod!

Spoiler:

Model M and "Row 6" (the tallest on the M2) cap profile comparison:

: Model M vs Row 6 profile; 2018-04-01 16.46.45.jpg (3.96 MiB) Viewed 6022 times

Assorted thoughts:

Sound is a lot less consistent than on a Model M; this is not as obvious when you're just typing along, but certainly is when you start comparing keys. Some are very pingy, others not at all.
The keyfeel is there and fairly consistent despite the variations in sound.
Delicate case construction compared to the M, be careful with those tabs.
Profiled keycaps because of the flat construction. They are one-piece thick PBT, retain the texture you know and love, but good luck finding replacements.

Regards,

Darkshado

j0d1 · 02 Apr 2018, 01:29

Fixing the SHIFT stabilizer

That one was easy. I applied a little bit of krazy glue and wait a few minutes.

It's head to see but the crack is filled with glue

: 22.stabilizer.fixed1.jpg (736.71 KiB) Viewed 6533 times

At some angles, it doesn't look cracked

: 23.stabilizer.fixed2.jpg (878.17 KiB) Viewed 6533 times

I did not have a lot of hope and I was ready to use some hot glue or melt the plastic with a solder iron.
I installed and removed it a couple of time and it works perfectly!

Fixing the springs

I won't be able to fix the springs and I will need to replace them.
Unfortunately I don't have spare ones so my temporary solution is to move those springs to the Scroll Lock and Pause keys that I never use.

Wrapping up for now

Until I find replacements for the springs, I decided to close the keyboard.

: 24.ready_to_close.jpg (1.31 MiB) Viewed 6533 times

Closing the M2 by putting the springs in the top case

: 25.mounting_springs.jpg (780.6 KiB) Viewed 6533 times

Ready to use!

: 26.done_1.jpg (1.72 MiB) Viewed 6533 times

: 27.done_2.jpg (2.01 MiB) Viewed 6533 times

j0d1 · 02 Apr 2018, 01:32

Darkshado wrote:But came up with the "zip tie" mod!

Oh that's very clever! I will need to re-open mine when I'll find spring replacements so I'll definitely try this!

Darkshado · 02 Apr 2018, 01:51

Thanks! Longer term it would be preferable to find suitable screws, nuts and washers to have a reusable solution.

depletedvespene · 02 Apr 2018, 02:03

Darkshado wrote: ↑ Reassembly is best done with something to raise the inverted top half of the case, e.g. these two yogurt containers:
2018-04-01 14.50.25.jpg

You may color me surprised: the M2's numpad actually supports a 20-key numpad! I wouldn't have expected it.