Repairing Thinkpad keys/Keyboards

[joe4227]

Could someone please point me to any forum info on repairing thinkpad keys and keyboards? I don't seem to be able to locate anything using the search function...

[kfzhu1229]

What part of the keyboard are you looking to fix? The keycaps/switches or the membrane? The former there isn't much substance to it as if its broken you just replace it. The latter can be quite tricky if u don't want an entire keyboard replacement.
I have JUST attempted to repair a T520 keyboard from shorted traces if that's what you are interested in

[RealBlackStuff]

Check on https://laptopkey.com/ for instructions.

[joe4227]

What part of the keyboard are you looking to fix? The keycaps/switches or the membrane? The former there isn't much substance to it as if its broken you just replace it. The latter can be quite tricky if u don't want an entire keyboard replacement.
I have JUST attempted to repair a T520 keyboard from shorted traces if that's what you are interested in

My Function key works, just needs the hinge replaced. However, since I removed that key to determine what was needed, the Left Control key ceased to work.
I removed the key cap, cleaned it, and verified that the hinge is okay.
But the Control key seems to do nothing. The key feels perfectly normal. But no effect - you get whatever other character you type with the Control (Control A, Control-V, etc.)
Why would it suddenly quit working. The keys on either side and above are all fine.
So, if it's not the cap/hinge assembly, and the pad depresses as normal, what to do?
These units aren't like the olden days of electronics with schematics available and traces to be followed and isolated - or are they?

Check on https://laptopkey.com/ for instructions.

Yes that site's fine if you're just replacing a cap/hinge. I remember seeing a site that showed how to replace the "cups" too, and gave more info on troubleshooting the traces, etc., but I think it's no longer online.

[kfzhu1229]

My Function key works, just needs the hinge replaced. However, since I removed that key to determine what was needed, the Left Control key ceased to work.
I removed the key cap, cleaned it, and verified that the hinge is okay.
But the Control key seems to do nothing. The key feels perfectly normal. But no effect - you get whatever other character you type with the Control (Control A, Control-V, etc.)
Why would it suddenly quit working. The keys on either side and above are all fine.
So, if it's not the cap/hinge assembly, and the pad depresses as normal, what to do?
These units aren't like the olden days of electronics with schematics available and traces to be followed and isolated - or are they?

Take the cup out and press it with your finger and see if it registers that way.
Passmark keyboardtest also helps you identify all the keys that don't work. Keep in mind though that special keys like fn, printscreen and sysrq may not be registered by the software properly and forward and backward keys will only show as a hex code. Moreover sometimes it detects control and alt pressed together on a Thinkpad keyboard and that is not your keyboard's fault, and depending on the layout some punctuation keys like ` and / may not be detected properly.
If you see regular keys like letters or numbers or F1-F12 that just won't register then it is most likely a problem with the trace.
Which thinkpad model keyboard are we talking about here?
If you think left control got damaged when you are trying to figure out the fn key then you can attempt lifting and separating the membrane in that area by removing both the keycap and the switches for Fn and control keys, and use a multimeter to see if the traces have proper continuity. Make sure the middle insulation layer is not in your multimeter's way.
If you detect a discontinuity on a trace, the circuit scribe silver pen (actually designed for children to be creative with learning about circuits lol) can fix this by just drawing on top of the trace:
https://www.newegg.ca/circuit-scribe-cs ... 6886445010
Fortunately for once Newegg Canada decides to be nice to Canadians and actually give us a much cheaper price than anywhere else! I originally thought this is a fake or something but rest assured I have used this to fix my T520 keyboard and this is definitely not fake!

[joe4227]

Take the cup out and press it with your finger and see if it registers that way.

I'll try the passmark kbtest thing.

Aren't the cups glued down? How do you take them off without destroying them?

I'm trying to get my head around how these things work. My knowledge of keyboards is quite dated. I understand the cap, hinge and cup.
But where's the actuation taking place? When I press the Function key Cup alone, with the cap and hinge removed, it works fine. When I do the same for the Control key it does not.
So, does the cup actuate the membrane? Or is there something more I'm not seeing?

[kfzhu1229]

Take the cup out and press it with your finger and see if it registers that way.

Aren't the cups glued down? How do you take them off without destroying them?

I'm trying to get my head around how these things work. My knowledge of keyboards is quite dated. I understand the cap, hinge and cup.
But where's the actuation taking place? When I press the Function key Cup alone, with the cap and hinge removed, it works fine. When I do the same for the Control key it does not.
So, does the cup actuate the membrane? Or is there something more I'm not seeing?

Depends on the model of ThinkPad you are working with. Older models like NMB made T2x/3x/4x keyboards have the cup weakly glued onto the membrane and you can easily pry it off and it won't be an issue as long as you position it properly before putting the switch down. The T4xx/T5xx series are a different story though.
So inside the membrane it is three layers. There is the top contact pad and the bottom contact pad, spaced out by a middle insulation layer that is cut circular around the contact pad to allow the pads to touch each other when a pressure is applied. When the cup goes down, it squeezes the top and the bottom layer together making a contact that way. When the cup goes up, the membrane goes back to its relaxed position which is the top and bottom separated by some micrometres of space created by the insulation layer.
By what you are saying it is most likely a membrane related trace fault.
Did the left control key work right before you were tackling with the fn key?

[joe4227]

Depends on the model of ThinkPad you are working with. Older models like NMB made T2x/3x/4x keyboards have the cup weakly glued onto the membrane and you can easily pry it off and it won't be an issue as long as you position it properly before putting the switch down.
Did the left control key work right before you were tackling with the fn key?

It's a T42 (2378-REU) from Sep. 2005. 15" Screen.

Yes, the Left Control was working right up until function key broke. No intermittence, no warning. The Function key works fine, but one of the little stubs on the side of the hinge that holds it onto the metal bracket is gone, so the keycap won't stay on.

That's what prompted me to search for a replacement keyboard. I figured if the trace had gone, other problems would also surface...
However, two years and two wrong substitutes made think I may not be able to get one.

[kfzhu1229]

It's a T42 (2378-REU) from Sep. 2005. 15" Screen.

Yes, the Left Control was working right up until function key broke. No intermittence, no warning. The Function key works fine, but one of the little stubs on the side of the hinge that holds it onto the metal bracket is gone, so the keycap won't stay on.

That's what prompted me to search for a replacement keyboard. I figured if the trace had gone, other problems would also surface...
However, two years and two wrong substitutes made think I may not be able to get one.

Oh you are talking about that one.
Then I believe when the key switch broke it scratched off the trace next to it and then your control key ceased to work.
A picture of the current situation with the fn key will help. Use external links to imgur or something instead, the 800x600 image limit on this forum for embed pictures means I can't see anything.

[JNavas]

Check on https://laptopkey.com/ for instructions.

Yes that site's fine if you're just replacing a cap/hinge. ...

Not really. Keycaps sold by laptopkey.com are cheap knockoffs that don't hold up.
Instead of being molded, the black on backlit keys is a surface layer that wears off with use.

Example of a key (N) with just 9 months of use.

Comparison of broken OEM left space key (upper) to replacement key (lower).
The replacement key is not backlit despite being ordered that way.

Caveat emptor!