Keys stop working all of a sudden

Por Driehoogvoor

Resident (52)

Imagen del Driehoogvoor

18-08-2014, 19:44

The keyboard of my F700D has some keys that have stopped working all of a sudden. My left shift, escape do nothing, the i key only every once in a while. The a and f keys are starting to fail too now. What could be happening? It has been working fine the last couple of days. Sad

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Por Driehoogvoor

Resident (52)

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18-08-2014, 20:49

Alright, I looked up some cleaning tutorials for old keyboards, and I have every key except for f and v working again. They're really responsive now, but I can't get any response out of the f and v keys. I've read something about applying graphite spray on the membrane, using the tip of a small screwdriver. Does anyone have experience with that?

Por AxelStone

Prophet (3064)

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18-08-2014, 20:51

The Sony HB-F700 is well known for it's keyboard failures (I'm sorry but its keyboard is really faulty). You must open it and clear carefully all contacts with alcohol. You can also improve the conductivity of the contacts writing with a soft pencil (2B) on them.

Good luck!

Por jltursan

Prophet (2580)

Imagen del jltursan

18-08-2014, 20:53

It's simply getting dirty after the recent use. It's simple to fix but somewhat tricky...

Open your keyboard, locate the failing keys and extract the key cap (be gentle!), then loose the keys switches, to do that you use a flat screwdriver and apply force to a pair of little tabs you'll find in two sides of the switch, eventually the switch will pop out the metal plate.
Now, using a soft rubber eraser try to clean the carbon contacts in the plate, Clean all the residues. Repeat the operation with the little contact pad under the keyswitch.
Restore the switch in its place and test the key, don't assemble again the keyboard until you get all keys working.

There're more agressive methods; but this one will be enough this time...

Por Driehoogvoor

Resident (52)

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18-08-2014, 21:15

I feel like I've tried everything on the F and V keys, but they simply won't do anything. I cleaned the contacts, tried restoring them with a pencil, cleaned the conductive part of the rubber caps, even tried using pencil on those, nothing works. Not even one occasional keypress, they're both completely dead.

What's the agressive method? I feel like I'm ready for that one. Wink

Por Driehoogvoor

Resident (52)

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18-08-2014, 21:45

After unscrewing over 20 screws, carefully prying the circuit board off of the membrane and using my voltage test screwdriver to find what part of the F and V keys didn't work (they share one are that had a dirty soldering point that I think was short circuiting something), I fixed it! They work! Now to put the thing together again.

Man, I feel like Repair Bas. Smile #Proud

Por Manuel

Ascended (18390)

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18-08-2014, 21:54

Congratulations! It is a great feeling to get something fixed Smile

Por Grauw

Ascended (10306)

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18-08-2014, 22:07

Haha this is the worst thing to happen in the middle of a coding spree, right? Smile Glad you got it fixed.

Por jltursan

Prophet (2580)

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18-08-2014, 22:34

Congrats!, you've finally done part of the "agressive" method, lol!
The complete procedure is unscrew the whole plate (phew!) and give it a try with contact cleaner spray. The contact pads in the switches can also be covered with silver conductive paint.

Por Driehoogvoor

Resident (52)

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18-08-2014, 22:56

Gah, it's still broken. The F and V keys didn't work anymore when I put everything back together. I unscrewed everything again, cleaned it again, then they worked, put it back together (testing every couple of screws if they still worked) and they stopped. Repeated that process again and now I can't them to do anything... Man, this is frustrating...

Por Driehoogvoor

Resident (52)

Imagen del Driehoogvoor

18-08-2014, 23:31

And of course it all works after you quickly throw it back together to try again tomorrow. Ah well, I'll just pretend that's how I fix stuff and forget this happened. Smile

I did learn a lot about the keyboard matrix, by the way. Everything on the same row is linked together on the circuit board, which was to be expected, but it's fun to see it nonetheless. Smile

And while we're on the subject: why do NEWKEY and OLDKEY exist in the BIOS when you can read the current state of the matrix directly via the PPI?

Oh, and fun fact: the F700D keyboard (KBD-12P) has two sets of contacts for the backspace key, but the key itself only triggers one of them. Weird, huh? They both work when you manually trigger them.