Thanks to old_hitech, I now have enough keyswitches to put my keyboard back into full service. After desoldering and testing all keyswitches on my last outing, I had put all the iffy or bad ones on the bottom row for easy removal. I now have the entire bottom row done, and they work.. but now I have lost my 1, 2, 3, 4 7, 8 ans - keys. Looking at the traces thoae keys all share one trace on the keybside of the pcb. I thoughr maybe one of the replcement keyswitches were bad, and found my replacement left shift switch was shorting a bit. Prior to this attempt the left shift had been just a dummy switch I had installed from among my dead ones just to fill the keyboard out. But removing the replacement did nothing. I changed all the TTL and the encoder just to be sure.. no diff. Ive checked continuity on the rest of the switches and nothing seems to be shorting.. so i am at a loss. Not good enough at reading schematics to divine an answer from there. If anyone has any suggestions I'd be most appreciative. I am sure it must be something with obe of the keys I changed.. prior to changing them I had tested those switches and verified they were still working. There aren't any special key switches apart from reset on that keyboard are there? Wondering if I accidentally subbed the wrong one into the wrong place.
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probably before attempting the PCBs in an Apple with soldering iron - i just recall the amont of postings in the last weeks related to stuff first working and then turning bad..... probably it´s a good idea to first do some more exercise in desoldering and soldering at a "practice"-board to gather more experience... and probably examining the tools you use with that tasks ?
Performing such tasks with missing experience or with bad tools is just the thing that will turn out as it did the last 7 or 8 postings .... things get worse.... so it might be a good idea to gather first some more experience before killing more hardware....
thats just a proposal.... bear in mind that even guys with several years of experience didn´t learn correct desoldering and soldering in one day and it´s realy a question also of having good tools ... not the kind of soldering iron with big tip and to hot because it´s not regulated and using huge amounts of soldering lead.... it´s realy more usefull to ruin dead boards as "practice"-boards and then afterwards when every soldering joint is perfect - to attempt the precious hardware you really want to get running again....
Yes, I'm not fantastic with soldering, but I have been practicing lots. I did a complete desolder/resolder of this keyboard with no problems before -- where I fall down sometimes is in testing -- I've blown a few TTL chips. But in this case, bearing in mind how close I came to losing this keyboard entirely, I was very careful and did everything by the book. Obviously I messed up somewhere.. now I just need to figure out where. I'm guessing it's a trace or short somewhere. More detective work. I've brought this keyboard back from worse.
if most famages now occur during measurements its quite good idea to turn back and
examine testing equipment.....
Most accidents are related to bad tools....
Using digital measurement equipment is a path avoiding one kind of accidents ( by dragging to much power from measured source with analog equipment ) :
and most accidents performing harm to tested units is using poor testing cables with long
metalpoints without isolation and by slipping off from the testing area prducing schortcuts....
So the testing cables should be as far as possible isolated with as small as possible microprobe points or clips that might be put into place without beeing connected to any measurement equipment until clip is fastened secure to pin that shall be measured and connecting that cables at end of measurementtool AFTER sure grip of the clip to the pin to be measured is guaranteed:
links are just provided as examples to compare and what to look for......
Thanks Speedy. I think I will indeed invest in better equipment.
As it turns out, I was able to dig myself out of the hole I had created. One of the traces leading from the affected keys had gotten scratched a bit. I soldered in a tiny bridge and it was fine.
I've posted pics for everyone above of my epic soldering job. I got the timer working again after taking the time to methodically follow esch trace. Because the pads were destroyed I needed quite a bit of jumper wire to make it happen, but voila! Only setback I had after that was not understanding how the repeat key was supposed to work. Honestly in 20 years I'd never had occasion to use one. On reading I realized you had to hit it and the key you wanted repeated simultaneously. I had thought just hitting the key and then following with the REPT was enough. Live and learn.
This Apple II is now back to original spec except for power supply. I am assuming I need a silver a2m001 unit?