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Thread: 1541 II Alignment - Cannot Read

  1. #21

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    Hoooo-kay so I'm back.

    Got a VGA converter only to find it didn't have an input to match my outputs... sooo
    I bought a Commodore - S-video converter cable

    That worked, and I'm back in business.

    So I went through and tried several disks, none of which worked. Exact same behavior for all of them.

    I don't know if this tells us anything, but I found a cleaning disk and did a load command on it just to see what would happen. It spun a few times but it did NOT rattle before coming back with the FILE NOT FOUND error.

    From that, can I deduce that it must have been at least able to recognize a regular disk when one was inserted? Does that suggest anything about the alignment or lack thereof?

  2. #22

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    Not particularly. With a cleaning disk all bets are off.
    I use my C128 because I am an ornery, stubborn, retro grouch. -- Bob Masse
    Machine room: http://www.floodgap.com/etc/machines.html

  3. #23

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    Quote Originally Posted by arcticfox View Post
    Hoooo-kay so I'm back.

    Got a VGA converter only to find it didn't have an input to match my outputs... sooo
    I bought a Commodore - S-video converter cable

    That worked, and I'm back in business.

    So I went through and tried several disks, none of which worked. Exact same behavior for all of them.

    I don't know if this tells us anything, but I found a cleaning disk and did a load command on it just to see what would happen. It spun a few times but it did NOT rattle before coming back with the FILE NOT FOUND error.

    From that, can I deduce that it must have been at least able to recognize a regular disk when one was inserted? Does that suggest anything about the alignment or lack thereof?
    Yesterday I've fixed a 1541C that didn't read any disk (errors were 23 and 27). The only thing that I needed to do was cleaning the head movement rails and tweak a bit the spindle speed.

    If you're absolutely sure you have good disks, then you might want to check if the R/W head isn't dead. It's very rare as fault, but it happened I've found one during my several repairs, you can find a video of it here:

    https://www.youtube.com/watch?v=1St7pqBJErY

    You need a multimeter to check the head's resistance.

    HTH
    Frank

  4. #24

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    Just for giggles I went ahead and did the test on the r/w head. Testing form the connector, and using the diagram from this site: https://www.retrohax.net/commodore-1...-fixing-chaos/

    I got the following results:

    R/W 1 to COM: 12.9 ohms (blue/black)
    R/W 2 to COM: 14.2 ohms (yellow/black)
    ERASE to COM: open (red/black)

    head_connector.jpg

    But that's assuming the pins on the connector align with the diagram. I know that's not a reliable assumption so I looked online for a maintenance manual. What I found was the 1541 Maintenance Guide from 1984 that shows an illustration of the connector, which measures all the resistances from the pin that's open on all the other pins.

    Now, this manual is for a classic 1541 and mine is a 1541-II so this illustration may or may not be correct, but if I picked the correct ground in the first place, then I have at least one measurement out of spec, where resistance is too low. In the illustration, the red wire seems to be ground. Maybe a shorted coil...

    What I really need is a manual specific to the 1541-II. I have the original user's guide but that doesn't have this sort of info in it.

    The search continues...

  5. #25

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    Quote Originally Posted by retro-pc_user View Post
    Found a service manual online:
    http://personalpages.tds.net/~rcarls...l%20(1985).pdf

    Error 27 refers to the stop adjust being out of range.



    Also, a video about aligning the 1541 Diskette drive:

    I've been trying to avoid the aligning solution but it seems I must. Thanks very much for this resource!

    And thanks again everybody for the suggestions. I'll report back again soon.

  6. #26

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    Apologies for the multiple posts...

    So I had managed to miss the excellent diagram in the manual provided by retro-pc_user. Going by that, it seems I have an open in the R/W head.

    Bah. So what I've heard about Mitsumi drives seems to be true in my case...

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