Cleaned a keyboard and won't work now - Is this possible to fix ?

skorpionrazor

24 Jun 2020, 07:35

This is my Acer 6312 - T42 / SP / US which I bought a year ago for a really good price.

Image

It was working fine But sometimes the left CNTRL key actioned randomly, and kept pressing for no reason, so I decided to dissassemble it and clean under the keycaps. Here is where things got bad.

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Although keycaps looked clean, undermeath them there was a kind of brown grease which was gross and really difficult to clean.
After removing the back plate and looking to the circuit I couldn't tell how 99% of the keys were working fine.

https://i.imgur.com/ANHdxIX.jpg (I don't paste the complete image because its going to overlap the hole post)

A yellow "liquid thing" like lubricant was covering part of the circuit, so I've tried to clean it carefully and assembled the keyboard.
(I wonder if this yellow liquid came with the keyboard from last owner he worked in an old restaurant so maybe the computer was exposed to dripping , vapors or thinks like that)

I don't know if keyboard came like that or it was my fault, because I remember trying to fix the CNTRL key issue time ago removing the keycap and droping a bit of WD40 cleaner like. Anyway, the keyboard still worked fine after that.

During the cleaning I've realized that membrane can be separated in two, like two membranes being stick together. So I had to dry in the middle of them too...

Unfortunately only the LEDs work :( I'm Not sure if there's still liquid causing trouble or what could it be.
So, the question is: Do you guys know a safe way to fix this? Is it safe to separate and clean the membranes where the circuit is and clean them somehow?

If you want to see the complete album images. Here's the link https://imgur.com/gallery/Vw8LHk6

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Weezer

24 Jun 2020, 08:31

Looks like because the keyboard uses a pressure based "edge connector" that there's most likely a contact failure on that point. When you reassembled the keyboard, was it screwed down tightly? If it was, I would check to see if there's dirt or grease on the contacts on the PCB and membrane.

As for cleaning the grease ***I*** use 50% isopropyl alcohol. I'm sure there is a better cleaner to use but isopropyl alchohol is decent at removing oil based residue and it's cheap and easy to get. If you decide to go down that route be sure to check with someplace inconspicuous first as alcohol can damage some plastic, and be sure to wipe down the areas you cleaned with a wet rag/q-tip/papertowel afterwards.

skorpionrazor

24 Jun 2020, 09:37

Weezer wrote:
24 Jun 2020, 08:31
Looks like because the keyboard uses a pressure based "edge connector" that there's most likely a contact failure on that point. When you reassembled the keyboard, was it screwed down tightly? If it was, I would check to see if there's dirt or grease on the contacts on the PCB and membrane.

As for cleaning the grease ***I*** use 50% isopropyl alcohol. I'm sure there is a better cleaner to use but isopropyl alchohol is decent at removing oil based residue and it's cheap and easy to get. If you decide to go down that route be sure to check with someplace inconspicuous first as alcohol can damage some plastic, and be sure to wipe down the areas you cleaned with a wet rag/q-tip/papertowel afterwards.
Makes sense... This was a few weeks ago and probably it wasn't screwed to tight or contacts on PCB were not correctly placed. I hope its just the PCB making poor contact.
Worst scenario would be grease in the middle of the membrane boards. If that's the case I'm not sure if I could separate them completely in order to clean there.(I tried but then I realized that there were like 2 circles in the middle that keep membranes stick together so I didn't want to force them)

I'll get the 50% isopropyl alcohol to clean the PCB first and update the thread if something happen.

Thanks for the support!

User avatar
BadCommand

24 Jun 2020, 23:06

Do the lock lights correspond to their respective state in the operating system? In other words, if you hook up a second keyboard and turn on Num Lock on that one, do both keyboard lock lights respond?

Weezer is right, I've had trouble with getting good contact with edge connectors before. Also make sure that you assemble the membranes in the right order, with the contacts facing each other (and the holey membrane between). Silly mistake, but it has happened before! Good luck with the cleaning.

skorpionrazor

26 Jun 2020, 09:46

BadCommand wrote:
24 Jun 2020, 23:06
Do the lock lights correspond to their respective state in the operating system? In other words, if you hook up a second keyboard and turn on Num Lock on that one, do both keyboard lock lights respond?

Weezer is right, I've had trouble with getting good contact with edge connectors before. Also make sure that you assemble the membranes in the right order, with the contacts facing each other (and the holey membrane between). Silly mistake, but it has happened before! Good luck with the cleaning.
Thanks!
Yes, I plugged a second keyboard and turning on Num-lock on that one both keyboards lock lights respond correctly (this is also for capslock and scroll lock keys) So.. Does this mean the problem is related to the membranes ?

I didn't try to clean it again because don't have isopropyl alcohol yet.

User avatar
BadCommand

30 Jun 2020, 23:05

My idea with the lock lights was just a first-order check if the controller wasn't fried. It's by no means a true verification. But it leads me to think that it's likely a contact problem, either between membranes or from membranes to controller. Especially since none of the keys work. Have you cleaned it further?

skorpionrazor

01 Jul 2020, 10:48

BadCommand wrote:
30 Jun 2020, 23:05
My idea with the lock lights was just a first-order check if the controller wasn't fried. It's by no means a true verification. But it leads me to think that it's likely a contact problem, either between membranes or from membranes to controller. Especially since none of the keys work. Have you cleaned it further?
I've just cleaned it again a few hours ago. Here are the results:

[Image]

About 80% of the keyboard keys work now. Which is a good sign. I used contact cleaner spray for the PCB contacts and cleaned membranes carefully with alcohol and dry them with a towel afterwards.
Now I have to find why those few keys don't work, but I think I'm in a good way.

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