Apple ][ Plus, Keyboard works (now) except Shift?

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Apple ][ Plus, Keyboard works (now) except Shift?

Recently, I got an Apple ][ Plus in externally decent condition, but internally not so great (lots of dirt and debris, some corrosion on the motherboard).  I've replaced the motherboard (tested to work, and boots).  The old motherboard has no video signal whatsoever, no beep (did beep for a bit, but then stopped).  Unfortunately, the Keyboard had been plugged into it backward (something that I didn't realize until I tried using it as a guide on the new motherboard).  The new board still boots.  But most of the keys didn't work (mostly the letters).  

 

Long story short, I ended up replacing both 74LS00s and the 74LS04 on the encoder board, as well as both 74LS257s at B6 and B7, along with the 74LS74 at B10. Tested the switches (all good), and replaced the ribbon cable (broken pin).  Things were better after that, but there were still some keys that were nonresponsive.  Then I noticed that the power light was cutting out when the ribbon cable was jostled, so I added some sockets in between the cable and the boards to give it a tighter fit.  Now everything works except the Shift keys?  

 

I should note that the Shift keys did work for a moment when I swapped back the old 74LS74, but others didn't.  I don't think the IC had anything to do with it, as several keys were nonresponsive, but all the functioning keys were working fine (including Shift).  I did try swapping them back, but it didn't bring back the Shift key, while the other keys that were nonresponsive remained nonresponsive.

 

I'm guessing that it's still a cable issue, but in case I'm wrong, maybe someone knows any other IC failures that could cause this issue?  Alternatively, if it is the cable (made it myself, so entirely possible), maybe someone could tell me which pin is responsible for the shift keys? At the moment, the only source I have for a new cable would have the same loose pin issues, so if I can figure out which pin, maybe I can address the issue until I can make a new one with better parts.

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The Shift keys connect

The Shift keys connect directly to the Keyboard Encoder chip so they don't go through the cable to the motherboard. If they are not working there is either a broken connection on the keyboard or the encoder chip is defective.

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Jeff is correct...  one

Jeff is correct...  one anecdote about ][+...

 

Someone I knew who was new to Apple ][ machines...  I think maybe he had used //e and //c in high school but never owned one himself.  Anyway, a number of years ago he bought a used ][+ and was complaining to me that it was broken and stuck in caps lock mode.  Shift worked on the numbers, etc...  but all the letters were always caps...

 

He had no idea that a stock ][+ didn't support lower case out of the box.  Anyway, I burned him a chargen 2716 with lower case in it and told him how to make the "1 wire" shift key mod...  and he was in business.

 

 

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jeffmazur wrote:The Shift
jeffmazur wrote:

The Shift keys connect directly to the Keyboard Encoder chip so they don't go through the cable to the motherboard. If they are not working there is either a broken connection on the keyboard or the encoder chip is defective.

 

 

Thanks!!!  I tested the traces on the keyboard and found no problems, so I tried some contact cleaner on the pins on the Encoder board and gave them a bit of a rubdown with some alcohol and the whole thing (Shift and all) came back to life!  

 

Still need to replace that ribbon cable though.  Even with the tighter fit of the socket, it keeps popping out of the motherboard.

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 DistantStar001 wrote:Still

 

DistantStar001 wrote:
Still need to replace that ribbon cable though.  Even with the tighter fit of the socket, it keeps popping out of the motherboard.

 

From the sound of it I think the motherboard socket may the problem. A new cable probably won't help. Unless you want to replace the socket, you could try using a machine pin socket as the go betweem. The larger pins should definitely keep it secured into the motherboard but you'll always have to leave it in there.

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