5.25 drive destroying boot-blocks

[spec@vax2.concordia.ca (Mitchell Spector)]

    I have a no-name 5.25 drive (seems to be a clone of the Disk II drive)
which is not able to boot most disks. After playing with it for a short
time, I discovered it was actually _destroying_ the boot blocks on any
ProDOS or DOS 3.3 disk it came across. If you listen, uou can hear it 
seek over the two tracks or so that it "eats" before going idle. :)

    In anycase, I assume it's a faulty 74xxx chip on the analog board of
the floppy drive (the controller works okay with one of my Disk II drives).
I had a quick look inside, all the chips are soldered-in, expect one.
Unfortunately the 74LS125 is soldered-in, and I would strongly guess this
is the chip doing the damage. Am I correct, or would it be another? I
didn't mark down what the one socketed chip is, but I'm sure I could
salvage a working one to try in the meantime.

Mitchell Spector
spec@vax2.concordia.ca