600XL keyboard issue

[600XL keyboard issue]

I have some ordered.

[600XL keyboard issue]

Haven't really read through this thread entirely.

But I think it's worth mentioning to check the two 4051 multiplexers.

I take it those interface between the keyboard and Pokey? It might be a while before I can really dig into this. It came with the video cable but not the TV switch box. I have an adapter coming from eBay. For testing I have been touching the center pin of the cable to the center wire of a coaxial cable. That Walter me test things, but doesn’t leave my hands free for troubleshooting. I tend to think the problem isn’t the keyboard because the keys that aren’t controlled by Pokey; SELECT, OPTION, START, RESET. work fine. They use the same mylar and connection as the rest of the keys.

 

So how do I test the 4051 multiplexers?

[600XL keyboard issue]

Thanks, that should let me determine whether it is the keyboard or something in the computer.

[600XL keyboard issue]

The new one costs more than I paid for the computer. Wouldn’t mind the price if I could be sure that is the problem. That is why I asked about shorting between pins on the keyboard connector.

 

You could have broken tracts on the Mylar. Not easy to repair, just order the new one.

[600XL keyboard issue]

Ok, I just looked at the Best site. I guess I would need the US QUERTY Mylar? I reseated all of the larger chips. It looks like all chips on mine are socketed. Still doesnt work. A couple of times when doing the keyboard test I have gotten random characters even without touching the keyboard. The sound, which I believe is a function of Pokey, does work. Is there a way to carefully short pins on the keyboard connector to simulate key presses? This would let me know if it is a keyboard or computer issue.

[600XL keyboard issue]

those keys are controlled by another chip (GTIA i think) whereas the rest are controlled by pokey.

as a quick test, remove the intermediate resistor board and plug the ribbon directly into the black slot on the motherboard - it might work for you like it has for others. it didnt work for me due to the severed pins under the motherboard slot but its easy enough to try and doesnt make any permanent changes.

That is what I thought I read somewhere. I was thinking that I need to look at Pokey. Maybe remove and replace a few times to make sure it is making good contact. Does that sound reasonable?

[600XL keyboard issue]

Ok, that sounds like a bit more than I want to do right now, but I will look at thing very carefully the next time I take it apart. Does the fact that the OPTION, START, SELECT, and RESET keys do work help to eliminate anything?

[600XL keyboard issue]

Ok, I tried that. There was definitely oxidation there. It still isn’t working though. How would I clean the socket it plugs into? Also, if that doesn’t fix it, what’s next? All of the keys to the right of the keyboard seem to work, except help. I was able to get into the self check menu and use SELECT to scroll then START to start the tests. I’m hoping that is a cle to the problem.

[600XL keyboard issue]

I bought a 600 XL cheap from an eBay seller. Once I found a TV that would let me set it to channel 3, the good news is that it works. Sort of. I can get the Ready prompt, but nothing I type in shows up. If I hold down OPTION while turning it on I can run the memory check and it passes. That is certainly good news. The buttons to the right of the main keyboard seem to work, but nothing else. How do I go about troubleshooting this issue?