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Joystick-UP & Alpha-Lock fix for STACKPOLE keyboard


jedimatt42
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I didn't see this info on mainbyte. It wasn't too hard to figure out from the theory on this page:

http://www.mainbyte.com/ti99/console/alpha_lock.html

 

But I thought I'd share a couple pictures of my alpha lock mod for the STACKPOLE keyboard.

 

Here is the keyboard back side. This seems to be a single sided circuit board, but with vertical jumpers all over the underside. This would be easy to just replace one of the jumpers with the diode, except the actual keys are all in the way, and I didn't want to take that apart.

 

post-42954-0-83624300-1441655528_thumb.jpg

 

Here, I cut the trace close to the place where I then scraped the far side bare, so I could solder the diode directly to the board.

 

post-42954-0-45543000-1441655806_thumb.jpg

 

There is clearly a more obvious and better place to cut the trace, closer to were I attached the diode. But this worked fine.

 

In case anyone was hesitant to perform the alpha-lock fix because it wasn't spelled out on mainbyte, here ya go.

 

(Only after this, did I notice how many game titles have - remove alpha lock on the title screen :) )

 

-M@

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When I was a kid, I did this fix and it lasted about 10 minutes and then failed. I tried multiple diodes, different diodes, etc. Upon failure, everything was lower case.

 

That is really unfortunate. I used the recommended 1N4148 diodes as pictured above by Omega.

 

I've been using it for more than a week now. It has worked beautifully.

 

There are many different models of keyboard for the 4a. Some provide easier locations to attach the diode than others. Cold solder joints could lead to the trouble you describe. Most programming or disk io wants you to enter in caps, and most games want alpha lock off. If you are hopping back and forth, the mod can be well worth it.

 

-M@

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When I was a kid, I did this fix and it lasted about 10 minutes and then failed. I tried multiple diodes, different diodes, etc. Upon failure, everything was lower case.

Yes. This happened to me when I performed the mod a few months back. I used diodes from two different sources and got the same problem. The strange thing is that it works great for about 10 minutes, but then every so often a lower case character appears until everything is lower case after around 15 minutes. Can any electronics expert explain this phenomenon? Maybe it's the keyboard? Mine's manufactured by General Instruments.
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