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Old 19 May 2010, 15:10   #1
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A1200 keyboard trouble

Greeting fellow Amiga fans,

I recently dug out my A1200 which is suffering from an odd keyboard problem. Every so often, it'll spit out a few random characters and then behave as if a key is being held down (usually "-", "*" or a number). This happens with both the original keyboard and a PC keyboard adapter - even with no keyboard at all. Looking at the schematics, I'm assuming it has something to do with the 68HC05 (U13) as there doesn't appear to be a lot more that could go wrong. I've had a 'scope on the KB_DATA line and sure enough you can see the extra pulses zipping along when it does its auto-repeat trick.

Now, if this was a DIP part I'd have replaced it by now but being SMD it's a little more tricky, so I'd like to be sure replacing it would fix the problem. Is there anything else that may cause these symptoms? There's also the matter of sourcing a replacement. I think I could get hold of a replacement 68HC05 easy enough, but it'd need programming. I'm guessing the only real option is to canibalise another A1200, or would one from an A600 work too?

Thanks in advance,

Old 19 May 2010, 15:19   #2
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Join Date: Jul 2003
Location: Helsinki / Finland
Age: 40
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Only the one from an a1200 will do. What kind of PC keyboard adapter do you have?
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Old 19 May 2010, 15:52   #3
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Originally Posted by Jope View Post
What kind of PC keyboard adapter do you have?
I believe it's a PC-Key adapter, just a uC on a tiny PCB which fits in the keyboard socket. It appears to work fine, although it seems to stay in caps lock when shift is depressed. I'm not sure if that's part of the same problem or the next one, lurking around the corner ;-)

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