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Wyluli Wolf

Help with Atari XE keyboard needed

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I'm having some issues with an Atari XE keyboard and I'm not sure what to make of it. It's one of those fold over Mylar jobs with the extra plastic piece in the center.

I plugged it in and the only key that worked is the HELP button at the top. None of the other keys respond while in basic or in the keyboard test app.

I took the keyboard apart and found that some of the traces were looking pretty corroded so I took some rubbing alcohol and cleaned the traces up best I could.

I then took a multimeter and traced the, errrr..traces all around the board to make sure they had continuity. I specifically traced the space bar key and a couple others and they all tested ok.

I plugged the keyboard back in and still nothing. Not one single key responds except the HELP button which takes me out of the keyboard test app.

I expected that at least ONE key would work to at least let me know that the Mylar sheet is indeed the issue. Since I can not seem to get a response from anything other than the HELP button (which, ironically, is of no help - haha) I'm not sure what the issue is. I don't want to purchase a new Mylar insert if that isn't going to resolve the issue.

Does anyone have any advice on what else I should try?

 

 

post-38599-0-31211700-1529614040_thumb.jpg

post-38599-0-01120800-1529614606_thumb.jpgpost-38599-0-10523900-1529614614_thumb.jpg

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Well, still not sure what to make of this issue. I could take a gamble and purchase a new membrane I guess. Found this on eBay and wondering if it will work. The membrane in my system has no part number listed.

 

eBay item (too bad shipping cost is so high..heck of a deal otherwise)

 

I see Best Electronics sells the membrane for $22 but I'm not sure if it would be better to get the newly manufactured one above.

 

Also, still open to any thoughts on troubleshooting further....

Edited by Wyluli Wolf

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Hi Wyluli Wolf,

 

have been looking at the image of the solder side of the board. Just above the Atari logo are two solder pads, and it appears that one of the legs from one pad has been folded over and is touching the other pad. May be nothing, but I would check this out as it maybe causing a short.

 

Regards

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Hi Wyluli Wolf,

 

have been looking at the image of the solder side of the board. Just above the Atari logo are two solder pads, and it appears that one of the legs from one pad has been folded over and is touching the other pad. May be nothing, but I would check this out as it maybe causing a short.

 

Regards

Too be honest I didn't really look it over closely at all. I focused entirely on the keyboard membrane. You appear to be correct. I'll fix the bridge but wonder if any parts will need to be replaced after. Guess first thing is first.

 

Thank You!

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Validate that you have continuity from the XE to the Keyboard:

Keyboard port (XE System Console only):

8 1
o o o o o o o o DA-15 Plug - male, with
o o o o o o o pin numbering reverse of standard
15 9
1. /K2 Keyboard Scan (POKEY) 9. +5V
2. /K1 Keyboard Scan (POKEY) 10. +5V
3. /K0 Keyboard Scan (POKEY) 11. KBDETECT (GTIA/FGTIA)
4. /KR1 Keyboard Response (POKEY) 12. NC Not Connected
5. /K5 Keyboard Scan (POKEY) 13. GND Ground
6. /K4 Keyboard Scan (POKEY) 14. NC Not Connected
7. /K3 Keyboard Scan (POKEY) 15. GND Ground
8. /KR2 Keyboard Response (POKEY)

Take a look at the the 130XE schematics and the various XL keyboard scan matrices out there. You should be able to short pins on the 24 pin connector to see if characters show up (to rule out the membrane) 4051s have been known to fail.
post-4566-0-83665600-1530061841_thumb.jpeg
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Found this for the pinout of the XE keyboard (which doesn't seem to match the one posted above).

post-38599-0-55417900-1530218599.jpg

 

I'm having trouble figuring which spots to "short" to see if the keyboard will respond. I did plug in the keyboard (removed the membrane first) and tried shorting various combinations of 2 pins on the J2 connector to no avail.

 

If I decide to replace the 4051's would these work?

eBay

And how about these if I decide to stock up on a cheaper option?

 

If there is enough room I'll solder in DIP sockets first, then install the new chips. After that I may purchase a new membrane regardless as mine does have a bit of corrosion and deterioration. If those two things don't work, well...pffft!

 

Thanks.

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Picked up and installed a new keyboard membrane. Exact same symptoms as the first post. Only key that works is the "HELP" button.

 

I have the following chips on the way. Hopefully they are a close enough match...

post-38599-0-68106100-1531940965.jpg

 

 

 

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Picked up and installed a new keyboard membrane. Exact same symptoms as the first post. Only key that works is the "HELP" button.

 

I have the following chips on the way. Hopefully they are a close enough match...

attachicon.gifkeyboardchip.JPG

 

 

 

 

Modern 400-series chips are fully interchangeable with vintage ones. I've used modern 4050's and 4051's several times to repair vintage Atari equipment, along with a 4011 in a CX-53 Trak-Ball.

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Replaced the Mylar with a nice new one. Replaced both 4051's with the chips pictured in my previous post. Still experiencing the same issue as in the first post. Only the HELP button responds. The back of the circuit board (pictured) does have pins bridged (see above and below the Atari logo). Not sure if this matters. I tried to remove the bridge but it's proving almost impossible as the solder doesn't want to clean up off the board. They appear to have been bridged originally...

Any other thoughts? Is it possible it's not the keyboard but something inside the XEGS?

I thought about buying the TKII PS/2 Keyboard adapter so I can at least play games with the UNO cart, but this won't do any good if it's something internal that is "broken".

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Bump...still seeking any advice. Thanks!

Assuming you have power going to the keyboard in the proper lines and that you tested continuity of the cable my guess would be pokey. And since you have a new mylar, we can rule that out. If you had another xe you could rig up the db15 connector directly to the pokey in the other unit.

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Yeah it might be a bad PoKey chip. :( Or it might not.. Do you have a logic probe?

I'm afraid I only have one XE system and I do not own a logic probe........

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