smith@nrl-aic.arpa (Russ Smith) (11/12/87)
I have a 3.5" disk drive that is giving up the ghost in a seemingly bizarre manner so I thought I'd pose the problem here to see if anyone else has experienced this or knows of an economical solution. Pardon the length, but there is no better way to describe the problem other than the (impossible) in-person demonstration... Background info: The drive used to be the internal drive of an Amiga that I bought at a "Consolidating Inventory" auction (no snide remarks re Commodore please...). Anyway, it started to exhibit intermittent problems as soon as we tried it out: sometimes wouldn't recognize the disk type inserted at all, sometimes would read along merrily for a short while, sometimes worked for hours on end. In all cases, the behavior was read/write related (as opposed to, say, disk sensing or whatever). Also in all cases there does not appear to be a temperature relation (the thing sometimes worked immediately on power up (cold), sometimes after being on for a while (warm), sometimes not at all). By the way, the heads are probably the cleanest in the country (the FIRST thing I tried) so that's not the problem. I removed the drive from the Amiga and replaced it with a working external drive. The problems also moved...i.e., it IS the drive that's the problem, not some set of chips/things internal to the Amiga. Except for certain physical characteristics (bigger disk eject button on one) the two drives were totally compatible (a lead-in fact for a following question). Foreground info/possible red herrings: The drive is part of a system bought at an auction. It DID NOT have a head protector installed when purchased, so was probably bounced around quite a bit from place to place (the warehouse guy where we picked it up, for example, was in a VERY foul mood and was quite rough with all items, probably including this one). However, this system may have been DOA when the computer store tested it since it was very clean when WE bought it. I mentioned above that the heads were clean...this is due to the fact that the first thing I tried was a few dozen passes with a cleaning disk WHICH SEEMED TO WORK! That is to say, inserting and removing a disk a "few" times actually "fixed" the problem a few times. This remains the standard fix I use when trying to debug the thing... The manufacturer is either NEC or Matsushita (I forget which manufactured which drive, but it was one of these two). I used a commercial disk copier package (Marauder) to do an RPM check of the drive. Though not distant from the RPM of other drives I have available, I remember that it may have been the lowest of the bunch. Okay, now my questions: (1) Has anyone experienced intermittent problems similar to those described above and found an economical solution? (2) One possible solution is to junk the drive and replace it. Given that the two drives I played with were compatible, would this hold for other drives as well? Is this an economical solution? Are either of these maker's drives KNOWN for their problems? (3) One guy I talked to (actually prior to this problem but on a related subject) said that 3.5" drives can't be "aligned". Given that this drive MAY have been wacked out of some sort of alignment by rough treatment this would be a potential fix. Was his statement true? If not, how does one align one of these things "to spec"? (4) The drive sometimes works on first attempts, sometimes after inserting and removing a disk a "few" times, which COULD be the exhibition of a vibration-related problem. Any clues there? (there are few to no socketed chips in the drive, the power and data plugs have been repeatedly pulled and replaced, hence any vibration-related effect would probably be elsewhere...where?) (5) The RPM of this thing may have been the lowest (but not by much) of all I tested (4). Could an intermittent problem of this sort be caused by too slow rotation of the disk? Can the RPM of the drive be increased? (there appears to be ONE variable component, either resistor or capacitor, on the drive: what is it for? Could adjusting it help? How?). As the above implies, I am not afraid to get into the hardware of this thing, I just don't know anything about 3.5" disk drives. The thing was relatively easy to remove from the Amiga (and replace). It appears that "many" manufacturers make pin-compatible drives. There is SOME sort of adjustable thing on the drive(s). I *am* having intermittent problems with one of them...any hints, past experiences (for example, with computer repair services (I've NEVER had a computer or peripheral repaired by someone other than myself so am totally umfamiliar with costs/reliability of these services)), replacement costs/suggestions would be VERY appreciated. Again, pardon the length, but multiple postings of this problem on local BBSes have not resulted in useful responses, so I thought I'd try this much wider audience. Russ <Smith@nrl-aic.arpa> JAYCOR Navy Center for Applied Research in Artificial Intelligence (whew!)