Did I just break my model M?

[DzR]

So I managed to get my hands on two IBM Model Ms from 1997. One seemed to be in good condition, all keys working, except numpad minus and plus, which I assumed was because the plastic rivets fell off.
The other one has a few keys that aren't working at all: (Esc, Tilde, Tab, 1, q, a, z, F7, F8, O, L, <.

After opening them up I went ahead and cleaned them using water and soap on the keycaps and on the case. The rivets seem mostly in place so I didn't take it apart further.

This is where my issue starts: While letting the case dry I wanted to see if a little pressure near the numpad would fix the minus and plus keys but when plugging the cable in the keyboard most keys wouldn't work (from the top of my head scroll lock worked, left shift, a few letter keys). I unplugged the cable and turned it upside down. After plugging it back in no keys worked.

I was gentle throughout the process, knowing this is an old keyboard but to go from no issues to broke in a few minutes seems fishy to me.
Any thoughts on what the problem might be? If I did break something, is there a way to maybe grab parts of the second one to fix the first?

Thanks

[fohat.digs]

Do you know about seating the key stems? When pressing the key back into place, the spring has to be centered just right. If your non-working keys do not click and sound and feel like the working keys, then the stems are not seated properly. Sometimes it can take several tries. Try standing the keyboard up on its front or back edge to get the spring to flop forward or back when replacing the key.

If you are plugging a PS/2 into the motherboard, that should not be done hot. You should turn off the computer, plug in the keyboard, and allow it to be found on boot-up. A USB connection is OK to hot-plug.

[Maledicted]

If you are plugging a PS/2 into the motherboard, that should not be done hot. You should turn off the computer, plug in the keyboard, and allow it to be found on boot-up. A USB connection is OK to hot-plug.

I haven't even thought of the fact that people may not just already know this. My first desktop computer still came with a PS2 mouse and keyboard. I imagine that's entirely alien for some people now.

Fohat's probably got it. Those keys may have all worked before the boards shipped. If Ace Ventura did the deliveries, they could all need proper reseating.

[DzR]

None of the keys work anymore. I tried it with reboots in between and hot-swapping and nothing. I also tried swapping cables between the two.
If I plug a usb keyboard I can get all three lock leds to light up so I can rule out a bad ps/2 port.

[Maledicted]

None of the keys work anymore. I tried it with reboots in between and hot-swapping and nothing. I also tried swapping cables between the two.
If I plug a usb keyboard I can get all three lock leds to light up so I can rule out a bad ps/2 port.

I'm not sure whether or not it is as important on a Model M as an F XT, etc, but is the grounding strap/cable attached to the plate again? Have you double-checked that the membrane contacts that plug into the controller aren't oxidized/damaged and are fully inserted?

[DzR]

Grounding cable is attached to the base plate and I used some sandpaped on the tab to make sure it's metal on metal.
Can't really check the contacts as it's still fully OEM, so plastic rivets still intact.

[Maledicted]

Grounding cable is attached to the base plate and I used some sandpaped on the tab to make sure it's metal on metal.
Can't really check the contacts as it's still fully OEM, so plastic rivets still intact.

You didn't touch the controller at all? It is outside of the plate sandwich. The membrane should curl to connect to it.

[DzR]

Haven't touched a thing besides the keys,caps and case. The controller seems to be held firmly in place, didn't want to start tugging on it as the plastic tabs seem easy enough to break.

[Maledicted]

Haven't touched a thing besides the keys,caps and case. The controller seems to be held firmly in place, didn't want to start tugging on it as the plastic tabs seem easy enough to break.

Any other ideas from people who know Model Ms better? Bad membrane? bad controller?

[DzR]

Most of the guides I've seen deal with earlier model m versions. Is there any way to swap the controller between my two boards, without breaking something or taking off the back plate ?



Also is there any way to fix the broken membrane of my second keyboard? I'd order from unicomp but the shipping is 3 times the value of the membrane.

[Leslieann]

Two things.
PS2 must be connected before Bios.
If you disconnect it some boards will reconnect it, but if it's not plugged in before bios you will have no luck no matter how many times you try. Turn the system off, plug it in then boot the system. This is why many owners use Blue Cubes, it converts it to USB and allows hot swap.

Second and this is important.
Model M's need a LOT of power, especially older models. Newer ps2 ports only provide about 1/10th the power that systems back then offered. Sometimes you get lucky and it works, other times you don't. This is the second reason many use a Blue Cube. The bluecube is one of the few PS2 to USB converters that can pass enough current, most converters can't. Too low of power can cause all sorts of issues from some keys working to none at all.

[DzR]

Things I tried:
-Swapping cable
-Plugging it in before POST
-Reseating key stems

The problem is with board #1 and not the setup as a whole as  keyboard #2 works (minus the keys with the broken traces, I'm assuming).

This board worked when I got it. I cleaned the key caps and stems and used it for a couple of days afterwards. When I got the hex key I opened it up to wash the case. While the case was drying to the side, I plugged the board back in and only a few of the keys were working. I unplugged, inspected the keyboard and when I plugged it back in, no keys were working.


-

[Maledicted]

Most of the guides I've seen deal with earlier model m versions. Is there any way to swap the controller between my two boards, without breaking something or taking off the back plate ?

Also is there any way to fix the broken membrane of my second keyboard? I'd order from unicomp but the shipping is 3 times the value of the membrane.

Being that late, and seeing that picture of the controller, that thing must have been made by Unicomp. It looks like you would just bend the clips that hold the controller to lift it out and swap. I found a guide that sort of shows it, but it was made by he who shall not be named. Other threads suggest that the membrane's contacts actually are just pressed against more contacts on the controller by a piece of foam, so nothing more than pressure actually holds them together. I didn't even know Unicomp used such a different controller.

You can try this: 4.0 MIL EMI EMBOSSED COPPER SHIELDING TAPE, 1/2" X 18 Y. Hasu appears to have suggested it in another thread. These would work as well: Conductive Pens, but the result is not flexible, which can be a problem with membranes.

[DzR]

Being that late, and seeing that picture of the controller, that thing must have been made by Unicomp.

It's still IBM, since from what I read they made them up untill 1999 in the UK, where this was actually made. But yeah, it looks like this generation is what Unicomp based their production on.

It looks like you would just bend the clips that hold the controller to lift it out and swap. I found a guide that sort of shows it, but it was made by he who shall not be named. Other threads suggest that the membrane's contacts actually are just pressed against more contacts on the controller by a piece of foam, so nothing more than pressure actually holds them together. I didn't even know Unicomp used such a different controller.

Thanks for the reply. i tugged on the controller after releasing the latch on the left and it came off rather easily. Indeed it seems that the membrane is sandwiched between a piece of foam and the contacts on the back of the pcb.


After I replaced the controller with the known good one it's still not working so it's most likely the membrane at fault. I'm currently contemplating if worth trying to repair, as the traces near the connector look somewhat oxidized and if the break is there I don't expect any fix to last for a significant period of time.

I'll probably end up ordering two membranes from Unicomp, fix up and bolt mod both, sell one of them off to break even if I can.

[Maledicted]

After I replaced the controller with the known good one it's still not working so it's most likely the membrane at fault. I'm currently contemplating if worth trying to repair, as the traces near the connector look somewhat oxidized and if the break is there I don't expect any fix to last for a significant period of time.

I'll probably end up ordering two membranes from Unicomp, fix up and bolt mod both, sell one of them off to break even if I can.

Before you do that, there's a trick you can try with oxidized contacts. If you've got a pencil eraser around, you can give the contacts a good stiff rub down with it, and it should clean them up nicely. If that's not available, I have even had some luck with isopropyl and some elbow grease.

[DzR]

Thanks for the tip, will definitely try it.
'll get the screws and drill bit this week so I can put it back together afterwards, in case I'm successful.