Posted By
h.batto@esteleban...
on 2019-01-21
03:50:36
|  Keyboard Failure
Hello everyone, i have a working Plus 4 but unfortunately the keyboard is not working, TED Checked, CPU Checked, Ferrite Beads checked, Ribbon checked and i swapped 6529 single port interface ICs and still nothing. what do u suggest? do u think burning a new PLA could helps?
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Posted By
crock
on 2019-01-21
03:52:48
 | Re: Keyboard Failure
Do your joysticks work? PLA is possible if it's not asserting the chip select for the 6529.
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Posted By
h.batto@esteleban...
on 2019-01-21
04:07:07
| Re: Keyboard Failure
Unfortunately i don't have joysticks. but i did a swap between my C16 and +4 for the TED and CPU but today i will try to swap the PLA too
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Posted By
crock
on 2019-01-21
07:20:26
| Re: Keyboard Failure
Have you ruled out the keyboard itself? Have you measure the resistance across the pins on the cable when pressing a key? It should be around 150 ohms and anything higher than about 800 ohms will give you problems. I've had KB's in the past whic have been kept in damp conditions where none of the keys made sufficient contact to work.
Have a look at my video here. https://www.youtube.com/watch?v=0iJZgKRIRsQ
At about the 5 minute mark I talk about measuring the KB resistance.
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Posted By
h.batto@esteleban...
on 2019-01-22
02:03:11
| Re: Keyboard Failure
Thanks a lot crock, i burned PLA on W27C512 eeprom and everything worked fine but it doesn't look in good shape  but at least my C+4 is back to life now. btw is there any fully compatible ROM to the original MOS PLA? so i can use it without messing the W27C512?
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Posted By
crock
on 2019-01-22
13:36:20
| Re: Keyboard Failure
Where in the world are you? I can send you one for the cost of postage plus a couple of beer tokens. Is your email address the same as your username? If so, I'll send you a PM.
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Posted By
h.batto@esteleban...
on 2019-01-23
02:15:12
| Re: Keyboard Failure
I am located in Lebanon (Middle East), thanks a lot i really appreciated.
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