Keyboard partial failure

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carlsson
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Keyboard partial failure

Post by carlsson » Thu Dec 11, 2008 11:31 pm

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.
Anders Carlsson

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Dbug
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Post by Dbug » Fri Dec 12, 2008 1:00 pm

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:

Code: Select all

FOR A=#C0000 TO #FFFF STEP 2
   CRC=CRC XOR DEEK(A)
NEXT A
PRINT CRC
Try on both machines, should give the same result :)

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carlsson
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Post by carlsson » Fri Dec 12, 2008 3:16 pm

Hm, thanks. In that case, I'd better save the little checksum program to tape since the faulty Oric won't let me type in the 2, S or X:s. Or actually the letter gets echoed, then the keyboard stops responding.
Anders Carlsson

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Post by highwayman » Wed Jan 21, 2009 11:13 am

i think i remember a ttl chip on the actual keyboard that does some scan decoding - replace that chip.

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Post by Twilighte » Sun Jan 25, 2009 6:17 pm

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.

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Post by highwayman » Tue Jan 27, 2009 10:32 pm

maybe the keyboard is sending control-characters that are being placed into the screen-ram and causing the video-chip to crash.

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carlsson
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Post by carlsson » Wed Mar 04, 2009 1:56 pm

I haven't investigated any further, but saw a thread on comp.sys.oric from September 2008 where another fellow had the exact same fault as I have (and my machine most definitely is not bought from him). So it must be relatively common, whether it is the 4051 or something else.
Anders Carlsson

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Post by highwayman » Sat Mar 07, 2009 4:58 am

if it turns out to be the rom then i can program one for you,
i even have the code for the updated one with the € symbol in it. :)

or i could put the 1.0 and 1.1 (oric1/atmos) code into a single chip with a switch on it. :)

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Steve M
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Post by Steve M » Thu Sep 24, 2009 1:45 pm

If interested I have spare Atmos keyboards.

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carlsson
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Post by carlsson » Thu Sep 24, 2009 2:37 pm

Thanks for the bump. I have not made any further attempts to fix the keyboard, but perhaps I will try later this fall. Can one retrofit an Oric-1 with an Atmos keyboard? I think I've seen that once, looking quite freaky.
Anders Carlsson

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Dbug
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Post by Dbug » Thu Sep 24, 2009 5:44 pm

The case is the same, the motherboard is the same: Open the box, remove the Oric 1 keyboard, replace by the atmos keyboard, close the box :)

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Chema
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Post by Chema » Fri Sep 25, 2009 9:48 am

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?

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Post by nobbysnuts » Sat Sep 26, 2009 10:57 pm

you are correct pins are shorter on oric 1 motherboard but atmos case will fit without any modification ,its not ideal but seems to work as I have converted a few recently and they work ok
ONLY DEAD FISH GO WITH THE FLOW

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carlsson
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Post by carlsson » Sun Oct 25, 2009 5:04 pm

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?
Anders Carlsson

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Post by Dbug » Sun Oct 25, 2009 5:16 pm

Maybe an issue with the small chip on the computer board, getting warm or something ?

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