18 May 2022, 07:23 | #1 |
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Join Date: May 2010
Location: Wichita KS, USA
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A4000 keyboard dead keys
So I finally got my A4000 out from the move and fired it up. Its been a couple of years and its been sitting in a box in the attic. I found that the top row of keys (escape key through F8) do not work. However, F9 and F10 work fine as do all the other keys. I ordered some silver paint and cleaned off the pads with qtips and distilled water and let it thoroughly dry before reassembly. There is no obvious damage to any traces.
Has anyone else encountered such behavior? Its weird that the keys affected are horizontal and only partial along that line. Any other recommendations as to what could be the problem are appreciated. |
18 May 2022, 09:24 | #2 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 43
Posts: 9,861
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It could be a break in the matrix between F8 and F9. Check http://eab.abime.net/showthread.php?t=81893 for a PDF of the keyboard matrix, it is the same for the 4000.
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18 May 2022, 10:08 | #3 |
Thalion Webshrine
Join Date: Jan 2004
Location: Oxford
Posts: 14,337
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You can buy replacement keyboard membranes for A4000 (which I believe is the same as A500) in UK they are £29 which is pretty expensive but cheaper than new keyboard.
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18 May 2022, 10:12 | #4 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 43
Posts: 9,861
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This will work for a very late model A4000 keyboard. The majority were PCB based.
A rough way to distinguish: metal springs, linear feel = membrane and rubber cups, clicky feel = PCB. |
18 May 2022, 16:29 | #5 |
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Join Date: May 2010
Location: Wichita KS, USA
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Thanks all! Definitely a membrane based board - I've had it a part a few times looking for obvious signs of damage. I'll look for one of those membranes for replacement if all else fails. I sure would love it if someone made a drop in mechanical board for these
Last edited by TheBilgeRat; 18 May 2022 at 16:30. Reason: Weird punctuation got trhu |
18 May 2022, 19:12 | #6 |
Amigan
Join Date: Feb 2012
Location: London
Posts: 1,309
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I would try cleaning the membrane contacts with 99% isopropyl alcohol and a cotton bud.
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18 May 2022, 20:01 | #7 |
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Join Date: May 2010
Location: Wichita KS, USA
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Tried that - no dice. They all were pretty dirty but the dead keys stayed dead. I'll probably try checking with a multimeter next to see if it's traces or the keys themselves
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18 May 2022, 20:44 | #8 |
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 43
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The membrane paint can dissolve in IPA, better just use a damp paper towel and quickly dry it afterwards with a dry paper towel.
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23 May 2022, 17:35 | #9 | |
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Quote:
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