04-22-2014, 01:48 PM
Warning! Contains geek content!
Got my friends Apple IIc opened up and the problem is a little more technical than I thought. The read/write head in the disk drive checks out as good. However it's position is off by two or three degrees. It was dead-on the last time I worked on it and there's nothing wrong with my work. Only two things can account for this part being out of adjustment. #1, the user tried aligning it but I can't see that as he's not a computer geek, not even electronically inclined. #2, it was dropped which I consider likely as there's a small crack on one corner of the case. It wasn't there the last time. Still, it's no problem. I can have the computer on with the diagnostic program running while I readjust the head azimuth to true. What makes that slightly interesting is the program disk can't be in the drive while I'm making the physical adjustments yet the program needs to be running. That's the wonderful thing about small programs. They can be resident in memory. No disk required after loading. Where it gets interesting is when the disk is put in and the drive door is closed. The rough position indicator vanishes from the screen and is replaced by a pair of precise position markers. As I slowly turn a screw on the control board a dot on the screen will get closer to or further away from a horizontal or vertical azimuth marker on the screen depending on which of the two screws I'm turning at the time. In the end the two '+' marks should be lined up on the single '-' mark. And since I've been typing this with one hand and making adjustments with the other hand I'm finished. It's done. The drive is aligned as close to perfect as I can get it. The only way I could get it maybe a fraction of a degree closer is with an oscilloscope, which I don't have. I'm running the test program now and it indicates the drive is within factory parameters. Am I good or what?
Got my friends Apple IIc opened up and the problem is a little more technical than I thought. The read/write head in the disk drive checks out as good. However it's position is off by two or three degrees. It was dead-on the last time I worked on it and there's nothing wrong with my work. Only two things can account for this part being out of adjustment. #1, the user tried aligning it but I can't see that as he's not a computer geek, not even electronically inclined. #2, it was dropped which I consider likely as there's a small crack on one corner of the case. It wasn't there the last time. Still, it's no problem. I can have the computer on with the diagnostic program running while I readjust the head azimuth to true. What makes that slightly interesting is the program disk can't be in the drive while I'm making the physical adjustments yet the program needs to be running. That's the wonderful thing about small programs. They can be resident in memory. No disk required after loading. Where it gets interesting is when the disk is put in and the drive door is closed. The rough position indicator vanishes from the screen and is replaced by a pair of precise position markers. As I slowly turn a screw on the control board a dot on the screen will get closer to or further away from a horizontal or vertical azimuth marker on the screen depending on which of the two screws I'm turning at the time. In the end the two '+' marks should be lined up on the single '-' mark. And since I've been typing this with one hand and making adjustments with the other hand I'm finished. It's done. The drive is aligned as close to perfect as I can get it. The only way I could get it maybe a fraction of a degree closer is with an oscilloscope, which I don't have. I'm running the test program now and it indicates the drive is within factory parameters. Am I good or what?
15 year veteran fire fighter
Collector of Apple //e's
Beatus homo qui invenit sapientiam
Collector of Apple //e's
Beatus homo qui invenit sapientiam