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Atrai 400 SELECT and OPTION Keys don't work


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#1 tezza OFFLINE  

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Posted Fri Aug 27, 2010 9:46 PM

Hi,

I just repaired a screen issue mentioned in another thread. The problem? A faulty ANTIC IC.

Anyway, on testing the unit after reassembling I noticed another unrelated issue. The SELECT and OPTION keys don't work. I'm not sure it they were working before I disassembled the machine, as I've never really given this micro a good once-over until now. They many have never worked in the time I owned the machine!

All other keys work including Shifted keys plus RESET and START.

Would a good assumption be a problem with the keyboard membrane or maybe that brittle (and bastard to get in and out) keyboard connector? I'm assuming that if all other keys work apart from those two the keyboard driver chips are likely to be ok...but then I could be wrong?

Anyone else had this problem or have any thoughts on the issue?

Tez

#2 atariksi OFFLINE  

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Posted Fri Aug 27, 2010 11:14 PM

Hi,

I just repaired a screen issue mentioned in another thread. The problem? A faulty ANTIC IC.

Anyway, on testing the unit after reassembling I noticed another unrelated issue. The SELECT and OPTION keys don't work. I'm not sure it they were working before I disassembled the machine, as I've never really given this micro a good once-over until now. They many have never worked in the time I owned the machine!

All other keys work including Shifted keys plus RESET and START.

Would a good assumption be a problem with the keyboard membrane or maybe that brittle (and bastard to get in and out) keyboard connector? I'm assuming that if all other keys work apart from those two the keyboard driver chips are likely to be ok...but then I could be wrong?

Anyone else had this problem or have any thoughts on the issue?

Tez


It could be cable or GTIA as GTIA controls the console keys-- START, OPTION, and SELECT. You can try grounding directly the pins on GTIA for S# to see if they give different values for: "10 ? PEEK(53279):GOTO 10".

#3 tezza OFFLINE  

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Posted Sat Aug 28, 2010 2:52 PM

I hear (and understand) what you're saying. It might be physically difficult to do though. I always worry that brittle ribbion which is the keyboard cable is going to snap if I play around with the innards with it still connected. It's hard to position the naked keyboard without putting strain on the ribbon.

I seem to recall in my last thread regarding the ANTIC chip someone mentioned an a 800XL GTIA might be backwards compatible with a 400 one? Anyone know for sure? I could then do a swap over and check that way as I have a 800XL (in fact I have two..one is a parts machine which could be a donor).

Tez

Edited by tezza, Sat Aug 28, 2010 3:32 PM.


#4 Rybags OFFLINE  

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Posted Sat Aug 28, 2010 6:31 PM

GTIA is the same as long as it's PAL or NTSC as per the original.

I highly doubt that's your problem though, it's much more likely mechanical or a dud/oxidized connection.

#5 tezza OFFLINE  

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Posted Sat Aug 28, 2010 6:42 PM

GTIA is the same as long as it's PAL or NTSC as per the original.

I highly doubt that's your problem though, it's much more likely mechanical or a dud/oxidized connection.


Yes, I would tend to agree. The SELECT and OPTION keys would have been thrashed in the day and I wonder if the membrane has just had it as far as those two keys are concerned. If it was a ribbon connection issue, I would have expected a few more keys to be down. They are the ONLY keys which don't respond, even if you clasp the membrane keyboard between thumb and forefinger and squeeze hard. RESET and START are fine.

Tez

#6 tezza OFFLINE  

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Posted Thu Dec 23, 2010 2:34 PM

Hmmm. I swapped out the keyboard with a replacement one but the problem with SELECT still exists. However I have discovered my initial assessment was wrong. The SELECT key is not non-working. It appears to be stuck ON !!

Oh well, a disassembly and diagnosis awaits after Xmas. Maybe it is GTIA after all?

Tez

#7 russg OFFLINE  

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Posted Thu Dec 23, 2010 6:53 PM

Hmmm. I swapped out the keyboard with a replacement one but the problem with SELECT still exists. However I have discovered my initial assessment was wrong. The SELECT key is not non-working. It appears to be stuck ON !!

Oh well, a disassembly and diagnosis awaits after Xmas. Maybe it is GTIA after all?

Tez

If it is stuck on, it is probably the mechanical key spring. Try tapping it several times and seeing if it seems to rebound.

#8 tezza OFFLINE  

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Posted Thu Dec 23, 2010 8:57 PM

Hmmm. I swapped out the keyboard with a replacement one but the problem with SELECT still exists. However I have discovered my initial assessment was wrong. The SELECT key is not non-working. It appears to be stuck ON !!

Oh well, a disassembly and diagnosis awaits after Xmas. Maybe it is GTIA after all?

Tez

If it is stuck on, it is probably the mechanical key spring. Try tapping it several times and seeing if it seems to rebound.


No, its a 400. Membrane keypad. Also it is a replacement keyboard as I thought the problem was the original keyboard. It would seem not, as this new keyboard does exactly the same thing.

Tez

#9 tezza OFFLINE  

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Posted Sat Dec 25, 2010 8:57 PM

Found the cause. Atariksi was right. It was the GTIA chip.

I had a spare working scruffy ATARI 800XL that I'd kept in case I need parts. I swapped out the GTIA chip in the 400 with the one in the 800XL. The problem now no longer exists on the 400 but the junk 800XL now exibits the symptom. The latter being a parts machine, this is of no concern. My 400 is fuly working again! :)

Thanks for the assistance.

Tez




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