| Apple II Clone - Keys Constantly Repeating, Help! [message #373375] |
Fri, 07 September 2018 02:01  |
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Originally posted by: Jordan
Hey all,
I bought a Japanese Apple II clone recently and am in the process of restoring it. It appears to have a dead power supply, so I've rigged a PC/AT PSU for the time being and sure enough it powers on to the Apple ][ prompt. Everything seemed to be working at first... until I hit "Shift" + "/" to get a question mark, at which point the computer started beeping rather rapidly and filling the screen with a combination of "?" and "/" line by line. Sometimes when this happens, the backgrounds of the characters are coloured too.. Hitting Return stops it. Hitting the "/" key without shift works fine. It also happens with some other symbols such as ">", but it doesn't happen with every Shift-modifiable symbol key - every alphabetical and top-row number key works fine with Shift.
I tried removing each logic and rom chip, dusting them + the sockets, and reinserting them but nothing changed. I also tried doing the same to the two chips on the keyboard PCB but still no change.
Here's a photo of the problem: https://i.imgur.com/QTMXTFH.jpg
I'm 99% sure the weird colour bleeding/artifacting/whatever is due to the cable I'm using. This clone has a 3.5mm headphone jack for video, and the cable it came with is fairly old and stiff.
It also occasionally immediately starts spewing question marks on boot until I hit enter, but this isn't a consistent problem like the one I described above.
So, any idea? Could the rom chips be failing, or is it maybe a memory problem? How would I go about diagnosing this?
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| Re: Apple II Clone - Keys Constantly Repeating, Help! [message #373404 is a reply to message #373375] |
Sat, 08 September 2018 08:00  |
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Originally posted by: R.Kiefer.SPAEM
Jordan wrote:
> So, any idea?
-12V ok? The keyboard controller doesn't work with a stable -12V (and
stable +5V, of course).
Mask ROMs normally don't fail. EPROMs do. If there is just a single
EPROM exchange that chip. I had several EPROMs elder than 20years which
lost parts of their content. You can program them again after erasing
under UV light. But you need the images. Japanese?
My next attempt would be changing the keyboard. Something inside which
is wrong there, i.e. a paperclip, coffee, coke ...
Regards
Ralf
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