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matsondawson
November 28th, 2010, 11:56 PM
Hi guys,

The 'R' key on a "mint" Atari 400 I bought off e-bay seems to be stuck.
I've unplugged the keyboard and it stops printing 'R's so I don't believe it's hardware.
Does anyone have any idea how to un-stick it?

NathanAllan
November 29th, 2010, 10:55 PM
You could try cleaning it up, those things are bound to get dusty after all this time. I don't own one anymore, and mine never had any keyboard problems, so I can't say how to do that.

And you are making me want another one :)

matsondawson
November 29th, 2010, 11:06 PM
You could try cleaning it up, those things are bound to get dusty after all this time. I don't own one anymore, and mine never had any keyboard problems, so I can't say how to do that.

And you are making me want another one :)

I'm not sure how to clean a membrane keyboard. I could possible remove the front of it (it's like a sticker) but I doubt it would go back on perfectly.

carlsson
November 30th, 2010, 03:16 AM
What is it líke on its back side, a circuit board that is held tight by a dozen small screws? If so, you might be able to disassemble it from behind and see if it can be cleaned on the inside without removing the front.

matsondawson
November 30th, 2010, 11:16 AM
Nope, no screws :\ All glue.

tezza
November 30th, 2010, 12:15 PM
I think a replacement keyboard might be the only solution Matt. It's the same for my Atari 400 keyboard problem where the Start key doesn't work.

These are not common in New Zealand. I guess if an old Atari 400 (with working keyboard) ever appears on our Trade Me site, we'd both be going for it. Us and quite a few others I think.

Tez

dorkbert
November 30th, 2010, 01:04 PM
sounded like you're in need of this --

http://cgi.ebay.co.uk/ATARI-400-REPLACEMENT-KEYBOARD-/120649499065

disclaimer: Not affiliated with seller, etc. etc. etc.

tezza
November 30th, 2010, 01:19 PM
Cool. Thanks! I bought it.

Tez

matsondawson
November 30th, 2010, 11:39 PM
I chucked it in the oven around 75 degrees C and the glue released so I could peal both layers off. Unfortunately it cooled while I was pealing the bottom layer and it left some track behind. But the keyboard still prints 'R's, even though R is in no way connected. I think there's a possibility of a hardware fault.

NathanAllan
December 2nd, 2010, 12:13 AM
Hmm. Reseating chips never hurt anything (as long as the chips come out and go back in well). First things first. Replacing the keyboard would be advisable.

Can you turn the computer on with the keyboard totally unattached, see if it starts then produces the R??

Can the 400 operate without its keyboard?? That will definitely tell you if it's in the keyboard or not.

matsondawson
December 2nd, 2010, 12:25 AM
Yes, it doesn't produce 'R's with the keyboard detached. It runs carts fine without it attached. Tessa is going to lend me his keyboard when his new one comes in to confirm it.

tezza
December 23rd, 2010, 11:39 AM
Just a follow up to this thread...

I swapped out the keyboard with the replacement one from the UK 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 !! Arrgg! *bangs head against the wall*

This might be a similar problem to Matt's.

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

Tez

vwestlife
December 23rd, 2010, 12:43 PM
Oh well, a disassembly and diagnosis awaits after Xmas. Maybe it is the GTIA chip?

On 8-bit Atari computers, the POKEY chip is in charge of keyboard input (among numerous other things). The GTIA chip does video output.

I know on the C64, its CIA chip can be destroyed by static electricity coming through the joystick ports, such as from accidentally brushing your fingers across the pins while reaching for the power switch. So maybe Atari's POKEY chip is prone to the same problem, because it is also in charge of joystick input, as well as the serial I/O (peripheral) port.

tezza
December 25th, 2010, 06:09 PM
Ok, fixed this. I suspected the GTIA chip as this controls the four control buttons on the right of the keyboard in the Atari 400. The POKEY chip controls the rest of the keyboard, and this was fine.

I had a spare scruffy (but working) Atari 800XL I'd saved for parts. The CTIA chip is compatible with the one in the 400. I swapped chips between machines. The 800 XL inherited the problem and the 400 is now fine!

Tez

NathanAllan
December 26th, 2010, 08:32 PM
Excellent! I have an 800XL that has a stuck key in it, not sure why so I will keep my eye on the GTIA chip when I gt back to it. Good job hunting the problem down. Troubleshooting is the name of the game.

channelmaniac
January 6th, 2011, 06:17 PM
If you have a logic probe you can use it to track down the keyboard inputs to the POKEY chip and see if you have a line stuck or not.

BTW: I have a 400 with a busted case here that I'll be scrapping. You're more than welcome to the keyboard.

tezza
January 6th, 2011, 07:29 PM
If you have a logic probe you can use it to track down the keyboard inputs to the POKEY chip and see if you have a line stuck or not.

BTW: I have a 400 with a busted case here that I'll be scrapping. You're more than welcome to the keyboard.

Mine is fixed now (see my post above). Matsondawson's problem is also fixed. I swapped my spare 400 keyboard for a few spare carts he had. It seems to work fine.

Tez