FelisSapien
Member
Hi all, since my last posts relating to the PSU I've had some fun getting the computer up and running. I'm now at a stage where as far as I can tell things are pretty good. I can boot to BASIC. I've verified the ROM contents. Basic memory tests pass. I'm feeling pretty chipper about things...
So now I turn my attention to the disk drives - I mean, I'll want to read and write data at some point, right?
Included in the bundle of bits I received are two disk II interface cards. One I can plug in and seems good. The other causes boot to fail. The only thing that seems odd is that the 74LS323 marked on the card reports to be a 74LS299 (according to Xgpro). The markings on the chips show AMD AM75LS23PC. Both fail logic tests in the same way. If I swap the chips between cards then the good card is still good and the bad still bad. So possibly there’s no issue here? I will order some spare chips and see what happens. I'm mostly ignoring the bad card for now.
If I use the good card and attach a drive then things start out looking reasonably normal. The disk spins, not crazy fast. Heads are moved back towards track 0 - I hear clicking for a second or two. But when I insert a disk… Nothing. Both drives behave in the same way.
I’ve tested 74LS125 on the analogue board (Xgpro) and the chip reports good. Flipping the drives over the speed visually looks about right. One thing that does look off, is the position of the track 0 marker on the cam. The technical manual I’m looking at suggests that this should rest just right of the cam follower. On both my drives it’s some way off, well in to ‘bad’ territory. I would adjust this but my gorilla brain can not make sense of the instructions given by the manual, which read:
To adjust the drive, unscrew the small screw (near the head on the sliding limiter - my interpretation) and move the cam. Be very careful, as this movement tends to damage screw threads all too easily. Once you have the cam adjusted, carefully tighten the screw again.
Now, I think I understand the words… but in practice I can’t make any change in where the track 0 marker is. Surely I’m missing something really obvious? I’m unable to find any clearer instructions (or videos) on this calibration step. I did locate some alternate instructions - The Basic DISK II Pages on the Wayback Machine but I can make no more sense of those.
Can anyone shed any light on what I’m supposed to be doing? Or offer other advice? Either on how to complete calibration or in further areas of investigation. I guess all the disks I have could be bad. At the moment I'm not sure I've a way to test this.
Onto general comments: At the moment the only way I have to get software to the computer is via the cassette port. I have a Floppy Emu on it’s way so at some point in the future I’ll be able to get s/w loaded on this computer. Am I right in thinking I need 64K of memory to use ADTPro? I recently missed a Microsoft memory card on eBay but will keep an eye out and bid harder next time.
I hope the above isn't too much of a ramble and makes some kind of sense. Thanks for the assistance - Carl
So now I turn my attention to the disk drives - I mean, I'll want to read and write data at some point, right?
Included in the bundle of bits I received are two disk II interface cards. One I can plug in and seems good. The other causes boot to fail. The only thing that seems odd is that the 74LS323 marked on the card reports to be a 74LS299 (according to Xgpro). The markings on the chips show AMD AM75LS23PC. Both fail logic tests in the same way. If I swap the chips between cards then the good card is still good and the bad still bad. So possibly there’s no issue here? I will order some spare chips and see what happens. I'm mostly ignoring the bad card for now.
If I use the good card and attach a drive then things start out looking reasonably normal. The disk spins, not crazy fast. Heads are moved back towards track 0 - I hear clicking for a second or two. But when I insert a disk… Nothing. Both drives behave in the same way.
I’ve tested 74LS125 on the analogue board (Xgpro) and the chip reports good. Flipping the drives over the speed visually looks about right. One thing that does look off, is the position of the track 0 marker on the cam. The technical manual I’m looking at suggests that this should rest just right of the cam follower. On both my drives it’s some way off, well in to ‘bad’ territory. I would adjust this but my gorilla brain can not make sense of the instructions given by the manual, which read:
To adjust the drive, unscrew the small screw (near the head on the sliding limiter - my interpretation) and move the cam. Be very careful, as this movement tends to damage screw threads all too easily. Once you have the cam adjusted, carefully tighten the screw again.
Now, I think I understand the words… but in practice I can’t make any change in where the track 0 marker is. Surely I’m missing something really obvious? I’m unable to find any clearer instructions (or videos) on this calibration step. I did locate some alternate instructions - The Basic DISK II Pages on the Wayback Machine but I can make no more sense of those.
Can anyone shed any light on what I’m supposed to be doing? Or offer other advice? Either on how to complete calibration or in further areas of investigation. I guess all the disks I have could be bad. At the moment I'm not sure I've a way to test this.
Onto general comments: At the moment the only way I have to get software to the computer is via the cassette port. I have a Floppy Emu on it’s way so at some point in the future I’ll be able to get s/w loaded on this computer. Am I right in thinking I need 64K of memory to use ADTPro? I recently missed a Microsoft memory card on eBay but will keep an eye out and bid harder next time.
I hope the above isn't too much of a ramble and makes some kind of sense. Thanks for the assistance - Carl