After some looking, I managed to find another pair of
identical TEC
FD-501 drives - these came from a MSI disk box which had stopped
working, and guess what - both of those drives do not work either
(jumpered exactly the same as my working ones).
That makes 5 out of 8 TEC FD-50x drives drives that I have come
across in the past year which are faulty - does anyone know if
there is a known issue with these drives?
A disk drive performs several different functions. In particular, it
rotates the disk, it detects the index hole and write protect notch, it
moves the heads between cylinders and detects the track0 position, and it
actually does the reading and writing.
Do you know which, if any, of these systems are working? Can you get the
disk to spin? Do you get an index pulse? Can you get the head to move?
And so on.
A drive exerciser is handy for this, but by no means essential. You can
often get away with just pulling pins on the interface connector low with
bits of wire connected to the 0V line. And look at the outputs with a
logic probe. Remembr there output drivers are open-collector, so you need
to add terminating/pullup resistors (traditionally 150 ohms to +5V) for
tssting.
Note that some drives with a big ASIC or microcontroller on them do some
kind of power-on initialisation. In particular, a few drives do odd
things if inputs are held active (low) at power-on. Other drives will
ignore all inputs if the power-on seek-to-track-0 fails.
If you have one of the latter units, you should be able to see
transitions on the stepper motor drive outputs just after power-on. And
you can check the track0 sensor by hand, of course.
So, I'm looking for (in this order):
- Technical information on the drives which would enable me to
repair these ones.
I can't believe it would be that hard to trace out a schematic. Even if
there's a big ASIC in the middle of the board (likely on half-height
drives), you can often figure out what it's doing from the surrounding
circuitry. You can at least check if things like senosr inputs do the
right things as you move a bit of card in and out of the sensor, etc.
-tony