Papalapa Posted October 30, 2021 Share Posted October 30, 2021 Recently I bought an Apple IIc with german keyboard and after some days of use the RETURN, ENTER and ARROW UP keys stopped working. I opened the Apple IIc case, unconnected the keyboard flat cable and visually checked for some damage, but all seemed to be correct. I applied Contact Cleaner (zero residue) to all the switches and after re-installing the keyboard again all the keys started to work. Today, after a couple of weeks using the Apple IIc, the problem has come back. What can be cause? Flat cable or keyboard controller chip maybe (which one in this case)? Quote Link to comment Share on other sites More sharing options...
Papalapa Posted October 31, 2021 Author Share Posted October 31, 2021 (edited) After checking with the multimeter, the PCB tracks and flat cable are OK so, I was thinking that the problem was the IC keyboard encoder. I also discovered that after turning off the Apple IIc and waiting around 2 hours, once has been startep up again the keyboard normally works. Then, after around 15 minutes turned on, the three keys stop to work. It's crazy! I released the drive unit to gain access to all the ICs in the motherboard, and after checking with the finger over the ICs I don't found any abnormally hot. While doing this I realized that the Apple IIc was turned on for more than 40 minutes and the theree keys continue working. Resuming, I realized that when the drive unit is released from the Apple IIc there's no problem and the keys work after 6 or 7 hours with the compter turned on so, it seems clear that the problem is the drive unit but I cannot imagine how can cause this kind of "delayed" problem in the keys. Maybe I have a ghost into the Apple IIc? Should I use the Apple IIc without the disk drive? Edited October 31, 2021 by Papalapa Quote Link to comment Share on other sites More sharing options...
trash_44fr Posted October 31, 2021 Share Posted October 31, 2021 Hi, I can't see a direct link between the keyboard fault and the disk drive... Maybe one track to follow : the //c is using two round metal washers to make contact between the disk drive and the ground on the motherboard. Misplacing them may result in short circuit. But it can't explain the delay. You can always try to remove them and do a test. My two cents ? Quote Link to comment Share on other sites More sharing options...
Papalapa Posted October 31, 2021 Author Share Posted October 31, 2021 7 hours ago, trash_44fr said: Hi, I can't see a direct link between the keyboard fault and the disk drive... Maybe one track to follow : the //c is using two round metal washers to make contact between the disk drive and the ground on the motherboard. Misplacing them may result in short circuit. But it can't explain the delay. You can always try to remove them and do a test. My two cents ? Yeah, I agree, it should be no relation between them. I'm sure that the two round metal washers are properly set because in fact, the original problem with this computer was that the disk drive always shown "Not bootable device". After some tests I discovered that the drive itself maybe touches any IC or part of the montherboard. After placing four 1,5mm. round metal wahsers in the four disk supports the problem was solved. I took care to keep in contact the two original washers with the ones that I added over them to don't loose the motherboard ground contact with the disk drive chassis, and that why I'm sure that the original whashers were properly set. Now that the computer works without the drive, I'll place the drive WITHOUT the Apple IIc cover and see what happens. The first problem with the drive was detected because the drive worked fine without the Apple IIc upper cover, but once set, the drive started to fail. That's why I suspected that the pressure of the cover under the disk drive makes something to go wrong. But this don't makes sense for me... Quote Link to comment Share on other sites More sharing options...
GameGeezer Posted November 23, 2021 Share Posted November 23, 2021 On 10/30/2021 at 11:49 AM, Papalapa said: Recently I bought an Apple IIc with german keyboard and after some days of use the RETURN, ENTER and ARROW UP keys stopped working. I opened the Apple IIc case, unconnected the keyboard flat cable and visually checked for some damage, but all seemed to be correct. I applied Contact Cleaner (zero residue) to all the switches and after re-installing the keyboard again all the keys started to work. Today, after a couple of weeks using the Apple IIc, the problem has come back. What can be cause? Flat cable or keyboard controller chip maybe (which one in this case)? You probably have a few dead Alps keswitches Quote Link to comment Share on other sites More sharing options...
Papalapa Posted November 24, 2021 Author Share Posted November 24, 2021 Problem solved. The last owner of the Apple IIc removed the cardboard between the bottom metallic shield and the PCB, and when the keyboard connector on the PCB is lightly pressed it contacts with the metallic shield and therefore some keys do not work. I'm lucky, this can be caused a shortcircuit in the motherboard... As I do not found the cardboard, I released the metallic shield and now the Apple IIc works like a charm. Quote Link to comment Share on other sites More sharing options...
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