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Thread: Tips on where to start on a non-working Disk II?

  1. #1

    Default Tips on where to start on a non-working Disk II?

    Earlier today, I acquired an Apple ][+ from its original owner. With it, I received three drives -- two Disk II, and a 1/2 height drive of a brand I've not seen before. One Disk II works just fine, the other does not.

    I'll disassemble it and clean the heads sometime this weekend. Assuming a thorough head cleaning doesn't do the trick, what other steps do those of you with more experience suggest I take? The drive does spin, but doesn't read disks at the moment.

    -Kevin

  2. #2
    Join Date
    Feb 2012
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    Northern Nevada
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    675

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    Here's the Sams Computerfacts for the Disk II: https://mirrors.apple2.org.za/Apple%...Apple%20II.pdf

    That should cover just about everything.

  3. Default

    Drive speed can also be an issue, speed should be set just a bit under the 300 Rpm mark

  4. #4

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    On getting a non reading Disk II, usually I try head cleaning then I next look to the 74LS125. Those are often damaged if the cable is plugged into the Disk II card incorrectly.

  5. Default

    Quote Originally Posted by troj View Post
    Assuming a thorough head cleaning doesn't do the trick, what other steps do those of you with more experience suggest I take? The drive does spin, but doesn't read disks at the moment.
    -Kevin
    Will it initialize a disk? Success at initialization but failure at reading all other disks is usually suggestive of motor speed that's out of order.

  6. #6

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    I need to find a proper fluorescent light so I can check drive speed manually. I tried Locksmith 6 and its drive speed test doesn't register anything at all.

    -Kevin

  7. #7

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    You can most likely make something with a small LED. You can take 120V AC 60Hz and use a 0.1 uf capacitor ( rated for at least 250V ), a full wave bridge rectifier and a 1k resistor. Put the 1K in series with the capacitor then an input lead of the full wave rectifier ( not just a single diode ). Put the LED on the output leads of the rectifier. The other input lead of the rectifier to the neutral lead.
    The resistor is to help absorb spikes. The capacitor is the main voltage drop. Use appropriate caution, dealing with 120V AC.
    It should make a useful strobe.
    Dwight

  8. #8

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    Try swapping the drives. Drive 1 plugged to the bottom, and Drive 2 to the top of your interface card. Then try and boot from Drive 2. If it works, then the problem is the interface card, if not then the problem is the drive. If it is the drive, then swap the analog cards between the two drives, and try booting again (do not replace the casing). If that works, then you can start swapping chips between the working, and nonworking cards to isolate the failed component. (note: do not attempt to boot from a disk that you can't replace/rewrite! As a defective a 74LS125 chip can corrupt data on the boot disk. If this chip is suspect, you will need to rewrite the boot disk with the working drive between boots). Also, be sure that the drives are plugged in properly as if they are offset on the controller card, the 5v rail will blow the 74LS125 regardless of whether that's your current problem or not. The next step, after you've eliminated defective ICs is to adjust the speed of the disk. To do this you will need a to write a diagnostic disk with ADTPro (DataLife Apple II Disk Drive Tester is recommended). You will need to boot from the working drive, then run your diagnostic on Drive 2 with the case removed. There are two potentiometers that will control the speed of your drive. The diagnostic software will tell you the speed as you adjust.

  9. Default

    Don't fluoro tubes already to that? If its got the pattern on the bottom of the drive spindle then it may not pop a lot, but it should highlight the correct pattern.

    A
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  10. #10

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    Most small fluorescent lights are high frequency and no longer flash at 120 cycles any more. They rectify the AC to DC, filter and chop it to a higher frequency, like a switcher supply does. Some large shop fluorescents will still have the regular ballast but I don't know of any small bulbs that would work. The LED method I stated should work. It is simple to make with parts that are easy to find.
    Dwight

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