conklin@eecae.UUCP (Terry Conklin) (01/18/88)
I just thought I'd mention this little tussle to the net. I don't know who other than myself makes major daily use out of their Mod I still, but hopefully you the reader will remember this little tidbit and pass it on. The Club, my BBS of many years, seems to burn out drives. Especially full height floppies. Granted, a floppy based system with an average of say 25 callers a day is getting a lot of use, but still, I was a little suprised when the first one died. But for one, all drives died of the same thing. The motor that spins the diskette would eventually wear, spin intermittently, and then fail outright. I had assumed that this intermittent spinning was the result of friction build up from the bearings and hundreds of thousands of stop starts. After yet another drive (#5) drive recently, I started swapping lots of drives and found the real culprit. The 7416 buffer/drivers that supply the signal for the disk drive cable had worn out. These drivers are easy to spot for the non-hardware hack on the Expansion Interface schemeatics. Looks for the lines with the floppy signals, and you'll see that all 8 (?) or so of them go through either of two 7416s. The 7416 driver problem was in fact a "characteristic" problem for Mod Is because of the length of the floppy drive cable. The chips on the expansion interface are located physically close to the floppy edge connector. What was happening, of course, is that as these chips grew old, and their performance waned, their output signal grew less and less acceptable, and less tolerant disk drives would "wear out" as the signal sent to them wasn't enough to start the motor. Given the age/time and such, this may occur to other Mod I's at this point in their life cycle. Terry Conklin ihnp4!msudoc!conklin (517) 372-3131 The Club conklin@egr.msu.edu