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Sent to me this morning after horrendous loss of all my work when my main drive died, by my friend Al. Thought it was worth sharing..

Assuming that you are prepared to write off the disk, there are a couple of things you could try. It's important to try them in the correct order, since they increase in risk until you reach the point where the disk is effectively destroyed. In no particular order, they are:

  •  Verify the disk is being cooled ... a failed fan is a common problem, and the noise of a bad fan bearing is often mis-diagnosed as a bad drive.
  • Change cables and terminators (cables, SCSI IDs and terminations are probably the major source of disk problems).
  • (SCSI disks only) verify the SCSI termination voltage (both at the computer and the disk). If the voltage is missing, try to determine why and fix the problem. If the voltage is too low, try enabling the termination voltage at both ends of the cable (this is not normally recommended since it can lead to a ground loop which increases noise levels).
  • Put the disk on a different power supply (usually by swapping it to another enclosure).
  • Try the disk on a different computer.
  • If "mechanical" noises are coming from inside the disk, don't run the disk until you've eliminated the source of the noise (or verified that the disk can be run without destroying it).
  • Physically remove the disk from all power sources, then observing proper anti-static precautions, carefully open up the disk enclosure. Determine whether the disk can be run with the case open (ie everything is screwed in tight). Some disks can be run with the case open. If the disk was making noises, try to determine the source. DON'T TOUCH THE PLATTER SURFACES! (Or allow anything to come in contact with them).
  • Assuming everything is screwed in tight, turn the disk over and shake it to see if anything falls out. If it does, try to determine what it is and where it came from. If it's an electrical component, chances are you may have to replace the electronics (with electronics from an identical drive).
  • Examine the platter surfaces for scratches (You will need a bench light or flashlight for this). If a surface is scratched by one of the heads (or arms), then that head is probably toast. Data on that surface is probably unrecoverable unless you can replace the head assembly and the scratching isn't too bad. If the scratching is severe enough to affect the rotation of the disk, then that arm may have to be bent or cut away to allow the disk to rotate properly.
  • Touching only the edge of the platters rotate the disk to check for sticky or rough bearings (use something extremely clean for this, hands aren't a particularly good choice, plastic (such as plastic wrap)is generally better but is a major source of static, so don't let it touch the electronics).
  • If the disk appears ok mechanically, then hook it up to power and turn it on. If the disks don't start spinning, try giving them a push. If that makes them go, then maybe the problem is the motor is no longer powerful enough to start spinning the disk.
  • You should be so lucky that the problem is a broken power lead, but hey, you should check anyway.
  • If the problem is the disk bearing (it's sticky or rough), then you could try an infinitesimally small drop of ultra fine machine oil on the bearing. This may smooth it out enough to run the drive long enough to get some data off.
  • If the problem is the head stepper motor assembly, then it is theoretically possible to replace the head and stepper with an identical unit from another drive. At a minimum this will require a good assortment of miniature tools. Given the alignment (and re-wiring) problems this will introduces, this procedure has a pretty low chance of success.
  • If there are no signs of mechanical problems then the problem may be with power. Perform a continuity check on the power and ground.
  • If there are no signs of mechanical problems, and you have power and ground continuity, then the problem may be with the electronics. Do a comprehensive visual examination of the electronics. Look for blackened or discoloured components, examine the traces on the board, look for signs of heat (melting, balled up solder, curled traces, etc). If you have an identical drive, then you may be able to swap the electronics (this may involve cutting, unsoldering and resoldering wires. Depending on the drive this may be fairly easy or virtually impossible). Also, note that drives which use EEPROM for various parameters may mean difficulty recovering data even if the drive is usable after the swap.
  • Connect the drive to power and check voltages (you will need a  meter for this). Check the electronics board, the stepper motor, and to the disk motor (assuming you can figure out where they are and can reach them). Check the fuses (if you can find them). If there is no power, you may be able to solder in a jumper wire to bring in power (or ground).
  • In all cases, you probably want a low level disk read/write diagnostic program to determine the effect of the changes you make.

I'm certain that I've missed or messed up more than a few of the suggestions offered here, so take all this advice with a grain of salt and a pound of caution. And of course, if you aren't a certified technician you shouldn't ever open up an electrical device anyway : ) ..

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