IBM Model M - powers on but bottom row of keys not registering

[freedom]

Hey guys, first poster here.

I recently rescued a 1991 IBM Model M from an abandoned building. I brought it home and gave it a nice (and careful) exterior cleaning. I plugged it in to find that it powers on just fine, keys register with the exception of the bottom row of keys (zxcvbnm,./) which do not register when pressed. I've tried resetting the key caps and have cleaned out the bottom tray when the caps are off, but I haven't opened the keyboard up yet. I am wondering what the solution to this may be before pulling everything apart. From my understanding so long as the PCB is good, it's fixable, but I'm looking for some options from those with more experience with Model Ms than myself. There are also a few springs that seem to need replacing due to being bent or stretched out, if anyone could give me some advice or point me in the right direction it would be greatly appreciated.

tl;dr IBM Model M powers on and most keys function, with the exception of the bottom row (zxcvbnm,./), seeking a solution to get it fully functional.

[E TwentyNine]

Those are definitely the only keys not working?  If not, take this program Aqua Key Test and run it, hitting every key.  Take a screenshot and post it here.

[Internetlad]

CTRL/ALT/SPACE etc work fine?

What about the up arrow and 123? Sounds like it could be a damaged membrane.

[freedom]

Those are definitely the only keys not working?  If not, take this program Aqua Key Test and run it, hitting every key.  Take a screenshot and post it here.

CTRL/ALT/SPACE etc work fine?

What about the up arrow and 123? Sounds like it could be a damaged membrane.

Here's an image from the aqua test. I guess there were more keys not registering than I thought! Any insight is greatly appreciated.

Just noticed it looks I have a left win key that works - it is actually my left alt which I have mapped to act as the left windows key.

[E TwentyNine]

OK, first what could be the good news.  It looks like you have entire traces out.  This is good because it could just be a problem at the connector instead of a break in the trace on the membrane.

After unplugging the keyboard, open it up.  You'll see two membrane connectors plugged into slots on the board (and maybe a third for the LED's but that's not important for this).

Pull the connectors, examine them see if they're corroded/dirty, examine the slots for same, clean if necessary (gently), reconnect everything.  Try the keyboard again.

Disable any mapping software you have, run Aqua again, post what you get (if different).

Edit: What's going on with F12?  Are you certain that registered?  Because if it did then your problem is not at the connector...

[freedom]

OK, first what could be the good news.  It looks like you have entire traces out.  This is good because it could just be a problem at the connector instead of a break in the trace on the membrane.

After unplugging the keyboard, open it up.  You'll see two membrane connectors plugged into slots on the board (and maybe a third for the LED's but that's not important for this).

Pull the connectors, examine them see if they're corroded/dirty, examine the slots for same, clean if necessary (gently), reconnect everything.  Try the keyboard again.

Disable any mapping software you have, run Aqua again, post what you get (if different).

Thanks for the quick reply! Unfortunately I don't have a 5.5mm nut driver to pull it apart today, do you know of one in particular that has thin enough walls for the Model M nuts? Preferably one that ships within America?

[E TwentyNine]

See the update in my reply regarding F12.  You might want to run Aqua again with any mapping software disabled.

Regarding a socket, couldn't help you there...

[dorkvader]

OK, first what could be the good news.  It looks like you have entire traces out.  This is good because it could just be a problem at the connector instead of a break in the trace on the membrane.

After unplugging the keyboard, open it up.  You'll see two membrane connectors plugged into slots on the board (and maybe a third for the LED's but that's not important for this).

Pull the connectors, examine them see if they're corroded/dirty, examine the slots for same, clean if necessary (gently), reconnect everything.  Try the keyboard again.

Disable any mapping software you have, run Aqua again, post what you get (if different).

Thanks for the quick reply! Unfortunately I don't have a 5.5mm nut driver to pull it apart today, do you know of one in particular that has thin enough walls for the Model M nuts? Preferably one that ships within America?

I bought a wiha precision one for use opening model M's from amazon.com not too long ago. I also often use the cheap ones that came with my cheap screwdriver set from China.
http://www.amazon.com/Wiha-96315-Precision-Metric-Screwdriver/dp/B001IULQFE/
http://dx.com/p/45-in-1-multi-bit-screwdrivers-set-yellow-black-42369

#2 I also use for bolt-modding, but the tips are too small for opening a model F (which uses a 9/32, I believe).

[freedom]

See the update in my reply regarding F12.  You might want to run Aqua again with any mapping software disabled.

Regarding a socket, couldn't help you there...

Ran aqua test again with mapping software disabled - same results with the exception of alt/win being swapped and f12 does not actually register, I'm not sure why it went to that dark grey in the original screenshot. So open it up and check the connections and hopefully that's where the issue is? I really appreciate you lending me a hand, and I will check in once I get a chance to open it up and check out the connections.

[freedom]

OK, first what could be the good news.  It looks like you have entire traces out.  This is good because it could just be a problem at the connector instead of a break in the trace on the membrane.

After unplugging the keyboard, open it up.  You'll see two membrane connectors plugged into slots on the board (and maybe a third for the LED's but that's not important for this).

Pull the connectors, examine them see if they're corroded/dirty, examine the slots for same, clean if necessary (gently), reconnect everything.  Try the keyboard again.

Disable any mapping software you have, run Aqua again, post what you get (if different).

Thanks for the quick reply! Unfortunately I don't have a 5.5mm nut driver to pull it apart today, do you know of one in particular that has thin enough walls for the Model M nuts? Preferably one that ships within America?

I bought a wiha precision one for use opening model M's from amazon.com not too long ago. I also often use the cheap ones that came with my cheap screwdriver set from China.
http://www.amazon.com/Wiha-96315-Precision-Metric-Screwdriver/dp/B001IULQFE/
http://dx.com/p/45-in-1-multi-bit-screwdrivers-set-yellow-black-42369

#2 I also use for bolt-modding, but the tips are too small for opening a model F (which uses a 9/32, I believe).

Excellent! Just ordered a wiha, thank you!