I just got a couple of nice Disk ][ drives off eBay-- the first-generation, metal-cased drives with the ribbon cables.
They're both clean and work perfectly, except the second drive won't write-- judging from the error messages I'm getting, it thinks all disks are write-protected. (IO Error 16 and the like).
Otherwise, it's perfect-- I can boot DOS, ProDOS, and Pascal from it with no problem.
I've checked with a multimeter and the write-protect switch seems to work fine, so I guess the problem is electrical. Any ideas?
Hello dramsey,
the notch protection switch passes along the disk analog board 2 pullup resistors
R9 ( 1k Ohm ) and R12 (10 k Ohm ) to a gate of the 74LS125 ( pin 2 and pin 3 )
and has influence to another gate of the 74LS125 at pin 8 and pin 9 before
signal passes to the disk controller.
So checking that 74LS125 and checking the values of the 2 resistors should
solve the problem and changing that 3 part should make the problem vanish.....
speedyG
.
Thanks Speedy..
Hey look! You can still buy brand new 74LS125s!
Except that it's not the 74LS125, because swapping this chip between the two drives didn't make any different.
R9 and R12 on both drives have the same values (R9 does show at 0.9K on my cheap multimeter)
I double checked the write notch switch and it's definitely working.
I can boot from the problematic drive, run COPYA to duplicate it to a disk in Drive 1, and then boot from that disk in either drive. I just can't WRITE to anything
Any other ideas?
UPDATE: It was the cable connecting the drive to the Disk II controller-- the problem moves with the cable. It's odd because there are no obvious physical problems with the cable, but there you go. Well, it's an easy enough fix.