Keyboard partial failure
Keyboard partial failure
This year I have increased my collection from zero to two Oric-1 computers: one loose and one boxed. I wrote about the loose one before, that it had problems displaying a colour picture on antenna signal. It seems to work better now, only that it strays in frequency so the TV needs to be calibrated now and then. I suppose buying/building a SCART cable is the obvious choice to solve that.
Now for my second Oric. It seems to mostly work fine: I can enter simple Basic programs, load tapes and all keys work except that a few ones makes the Oric freeze: 2, Q, S, X, ], \ and Cursor Down. If I press any of these keys, the cursor keeps blinking but no more input is possible!
I have disassembled the computer, carefully removed the motherboard from the keyboard connector and reseated it without any difference. Could this be a buggy ROM? I bought this Oric from a friend who has at least two more, of which one was earlier diagnosed as broken. If there is a keyboard fault, maybe we can switch motherboards.
Has anyone encountered this kind of error before? My other Oric doesn't behave this way, and if it is safe I could try to swap keyboard/motherboard between the two models. I'd rather not want to risk either half get damaged in case something is bad.
Now for my second Oric. It seems to mostly work fine: I can enter simple Basic programs, load tapes and all keys work except that a few ones makes the Oric freeze: 2, Q, S, X, ], \ and Cursor Down. If I press any of these keys, the cursor keeps blinking but no more input is possible!
I have disassembled the computer, carefully removed the motherboard from the keyboard connector and reseated it without any difference. Could this be a buggy ROM? I bought this Oric from a friend who has at least two more, of which one was earlier diagnosed as broken. If there is a keyboard fault, maybe we can switch motherboards.
Has anyone encountered this kind of error before? My other Oric doesn't behave this way, and if it is safe I could try to swap keyboard/motherboard between the two models. I'd rather not want to risk either half get damaged in case something is bad.
Anders Carlsson
I'd say that trying to swap the keyboards (just be carefull when removing/plugging the connector, the thing is fragile) is quite safe.
I suspect a problem with the keyboard, perhaps a short circuit on the keyboard circuit lines, in which case the suggestion would be to try the working keyboard on the non working Oric. (If it still fails, then you can probably assume that both keyboards are working fine.)
For the ROM hypothesis, I guess you could write a quick and dirty checksum program, to see if both ROM's give the same result.
Something like that:
Try on both machines, should give the same result
I suspect a problem with the keyboard, perhaps a short circuit on the keyboard circuit lines, in which case the suggestion would be to try the working keyboard on the non working Oric. (If it still fails, then you can probably assume that both keyboards are working fine.)
For the ROM hypothesis, I guess you could write a quick and dirty checksum program, to see if both ROM's give the same result.
Something like that:
Code: Select all
FOR A=#C0000 TO #FFFF STEP 2
CRC=CRC XOR DEEK(A)
NEXT A
PRINT CRC
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The TTL chip in question is the 4051 multiplexer(See page 257 of Leycester Whewells eccelent Advanced User Guide). It multiplexes the 8 row lines into a 3 bit that appear in the lower 3 bits of Port B in the 6522.
On the surface i can't see why pressing the keys would cause the system to hang thereon, but i guess the 4051 may just be screwed in this way.
On the surface i can't see why pressing the keys would cause the system to hang thereon, but i guess the 4051 may just be screwed in this way.
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- Flying Officer
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- Flying Officer
- Posts: 148
- Joined: Fri Oct 12, 2007 8:08 pm
Not sure about what I will say here, as I am talking by memory and all this was a long time ago.
Anyway I owned an Oric-1 which was converted to an Atmos with a kit that existed then. The thing is that the keyboard could not be replaced directly, IIRC. I remember they had to carry my Oric to an electronic store nearby to solder a bigger pin connector for the keyboard.
Maybe my memory is failing?
Anyway I owned an Oric-1 which was converted to an Atmos with a kit that existed then. The thing is that the keyboard could not be replaced directly, IIRC. I remember they had to carry my Oric to an electronic store nearby to solder a bigger pin connector for the keyboard.
Maybe my memory is failing?
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Today I had a reason to test my both Oric-1's. At first I tried the one that was known to fully work but which had problems outputting colour due to a bad RF modulator. It turns out to produce quite a decent colour picture even if there is quite a lot of pixel creep on the display.
Well, after a while I switched to the other Oric, the one with the malfunctioning keyboard. To my great surprise, it actually worked as it should. No keys were locking up anymore, and I could type and load any program.
Nothing lasts forever though. After having load and played a few games, the last one required me to press Return and the computer froze. After recycling the power, the bad keyboard problem was back. As soon as I press e.g. "2" or "A", it freezes.
I turned it off and switched back to the good Oric, played some more games. Then out of curiosity I switched back to the bad Oric which had been resting for a while.
Do you know what?! The keyboard now was working again. I loaded another game, but it froze. Then the keyboard went bad again. I managed to get it intermittently working though.
It has been some hour since my last try. I'm quite sure if I plugged it in again, at least in Basic it would work. What do you think is the cause, should I replace a ROM? It can't really be a short circuit in the keyboard mechanism itself as it suddenly works for minutes then goes bad again. Partial bad connection?
Well, after a while I switched to the other Oric, the one with the malfunctioning keyboard. To my great surprise, it actually worked as it should. No keys were locking up anymore, and I could type and load any program.
Nothing lasts forever though. After having load and played a few games, the last one required me to press Return and the computer froze. After recycling the power, the bad keyboard problem was back. As soon as I press e.g. "2" or "A", it freezes.
I turned it off and switched back to the good Oric, played some more games. Then out of curiosity I switched back to the bad Oric which had been resting for a while.
Do you know what?! The keyboard now was working again. I loaded another game, but it froze. Then the keyboard went bad again. I managed to get it intermittently working though.
It has been some hour since my last try. I'm quite sure if I plugged it in again, at least in Basic it would work. What do you think is the cause, should I replace a ROM? It can't really be a short circuit in the keyboard mechanism itself as it suddenly works for minutes then goes bad again. Partial bad connection?
Anders Carlsson