Amiga.org
Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: DiskChris on August 03, 2014, 05:20:09 PM
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So I turned on my amiga today to discover when I press either the "a" or "1" key it prints other characters on the screen....a toggles the caps lock and prints LKJHGFDSA while 1 prints =-0987654321'
All the other keys seem to work fine....I tried plugging in the keyboaord again....I don't have any other keyboards to test, but I'm thinking that since the rest of the keys work it sounds more like a keyboard short, so I think the amiga itself is probably fine??
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So I turned on my amiga today to discover when I press either the "a" or "1" key it prints other characters on the screen....a toggles the caps lock and prints LKJHGFDSA while 1 prints =-0987654321'
This is probably a short between the contacts of two adjacent keys or lines. Did the keyboard have contact with liquids?
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Actaully every key in the first row going down doesn't work 1,q,a, and z....pressing these send multiple key presses....and no liquid exposure
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I'm having trouble getting the keyboard apart....I got the case off, got all the pcb screws, yet I can't figure out how to separate the pcb from the keys?? EDIT: Nevermind it appears the keys are soldered to the board....DUH haha
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Are the A (Amiga keys) red? If so it is one of the rare Cherry keyboards that uses real contacts and not carbonized rubber.
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Nope A's are black....But I swear these switches are soldered....or am I missing something???
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A picture is worth a thousand words...
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Nope A's are black....But I swear these switches are soldered....or am I missing something???
Agreed that it sounds like a row/column short somewhere, else the keyboard microcontroller may have an issue. Liquid damage (coffee, fruit juice, etc) can easily cause this kind of fault as already mentioned. But this kind of damage is usually quite obvious when you open the keyboard.
Instead of attempting to completely disassemble it, why don't you try a more logical approach of measuring where the problem is? I forget the exact construction of the keyboard, but chances are that you can measure the rows and columns easily enough using an Ohm meter, or at least measure individual key switches/contacts.
As with pretty much every other keyboard on the planet, the theory of operation is just a scanned matrix. i.e. there are colums and rows, each of which are common to multiple keys, but any individual key press will connect a unique row to column combination, hence the microcontroller can figure out which key(s) are pressed, then it sends this serial data to the computer.
If the contacts all check out OK and you suspect a microcontroller issue, then you might be able to use one from an A500 keyboard. The serial protocol is the same between all Amiga models, not sure if the IC pinout will be the same as the one in the A2000 keyboard. If the part number on top of the IC is the same, then it'll be good to go.
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I sprayed a gallon of contact cleaner in there and it fixed it! But I seem to have lost one of those darn springs in the process....gonna have to cannobolize a pen :(
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http://www.ebay.co.uk/itm/Amiga-600-1200-500-repalcement-Keyboard-keys-all-amigas-includes-spring-clip-X2-/311020478906?pt=UK_VintageComputing_RL&hash=item486a43e1ba
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I sprayed a gallon of contact cleaner in there and it fixed it! But I seem to have lost one of those darn springs in the process....gonna have to cannobolize a pen :(
I did cut one into 2 halves and stretched them in my A500 - works but springiness lost a little.
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Great idea, eded up using a couple of the numpad keys as donors, I mean whoever uses those anyway:rolleyes: