User`s guide

1. The 74LS132 on the Disk ][ Controller card may have a blown gate or some
pins may be making poor or no contact. Try unplugging and re-socketing the IC.
This usually takes care of bad contact problems. (Or, you can replace the
74LS132 IC with another 74LS132 or 74132. A 74LS00 or 7400 may work, too.) Also
unplug and re-socket the 9334 and 556.
2. The ULN2003 IC on the Drive 2 main circuit board may have a bad gate or may
have developed some poor pin-to-socket contacts. Remove the drive cover. Unplug
and re-socket the ULN2003 IC. (Replacing a blown ULN2003 should not be too
difficult. Both Mouser and Newark carry the IC.)
3. Drive 2's cable may have developed a short between pins 14 and 16. Mark the
position of the cable at the Controller card and at the Drive 2 circuit board
and unplug the cable at each end. Use an Ohm meter to check for shorts between
adjacent pins. If you find a short between 14 and any other pin you can try
repairing the cable or cutting out line 14 and running a new lead; or you can
get a replacement cable.
______________________________
From: Rubywand
012- In connecting a second Disk II drive to my Disk II
card I misaligned the connectors. The result upon turning
it on was a static-like clicking noise. Now I can't load
anything from disk. Is the Disk II card dead? Are the IIe
and Drives all right?
Try removing the drive which was connected incorrectly. If your system
boots from the remaining drive (connected in the Drive One position), this is a
fairly good indication that the Disk II card and IIe are okay and that the
removed drive is messed up.
If it looks like a drive is bad, remove the cover and inspect the drive's
main circuit board for blown components. If nothing obvious shows up, a decent
fix try is to replace the 74LS125 IC on the drive's main circuit board. (Also,
see Q&A 013.)
______________________________
From: Ryan Underwood
I accidentally offset a row of pins on the //e disk controller card when
plugging one of the drives in. Snap, crackle... you get the picture. I opened up
my freshly fried Disk II, and in the center of the board there is a 74LS125 that
is blown. Replaced it (it was socketed) with the same chip from another Disk II,
and voila! it works again.
I would reasonably assume that misaligning the drive connector on the
controller is what blew the 74LS125 in several Apple II drives before they got
to me. Note that while the genuine Apple Disk II simply lights the LED and
doesn't move the head at all when this IC was blown, a Mitac drive actually ate
disks. So any number of dead Apple II drives with different symptoms could have
a blown 74LS125.