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Thread: MPI 360k won't read/write

  1. #11

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    Looking closer at the board, the device at the right, MC3470, is the preamp for the data read. With a disk having valid data on it and the head is loaded, you should see signals there with a scope. It will have a similar circuit to the pdf I pointed you to.
    Actually, you might start at the Read Data pin of the connector ( pin 30 ). Do this with a disk that has data. You should be able to follow the data path back to the preamp. You can use the pdf I posted as a rough guide, even though this implementation is different. It has to do similar things.
    Dwight

  2. #12
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    I think I've found the main part of my problem. While looking over the drive for broken wires, etc.. I noticed that the upper head was 'floating' above the disk, the little arm sitting above the 'shelf' it appears it would normally rest on. There is a tension spring and it seems to be not letting the head go down all the way. Anyway, when I used a wood dowel to get between the PCB and top of the head, and pushed it down gently.. suddenly it was reading the disk that was inserted!!

    I don't know what this portends for alignment... but that is the most I've gotten out of it in eons. Just gotta figure put how to adjust the spring.

  3. #13

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    Picture?
    Dwight

  4. #14
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    https://drive.google.com/file/d/1DwV...w?usp=drivesdk

    https://drive.google.com/file/d/1Dst...w?usp=drivesdk

    It's the head with the triangular cover there. If I gently push it down until the plastic arm on the left is resting on the 'track's under it, it reads. But if I release the head moves up and reading ceases.

  5. #15

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    It sounds like the head load isn't working. I doubt it is the springs fault. There should be a solenoid that is holding the head up.
    Do not remove the two screws holding things together or you'll lose the head alignment!!!!!!!!!!
    Can you get a better picture of the back where the two screws are?
    Also can you upload the pictures to the MB. Your pictures on the cloud can be lost, we want to show things for future reference. You can remove the two head connectors to fold the board back for a better picture.
    Dwight
    Last edited by Dwight Elvey; August 9th, 2019 at 09:10 AM.

  6. #16
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    falter,
    My MPI-51 has shunt 1G that selects which signal (Motor ON or Drive SELECT) loads the head by picking the Solenoid.

    7 jumpered to 8 is Motor ON
    1 jumpered to 14 is Deive Select

    If your drive has Shunt 1G check what is selected.

    Larry


    MPI-Shunt.jpg
    Last edited by ldkraemer; August 9th, 2019 at 02:15 PM.

  7. #17
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    So am I understanding that there is a solenoid that should pull the top head down?

    Larry where would I find this shunt?

  8. #18
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    My Shunt "1G" is on the Logic Board of my MPI-51 Floppy.

    What is the Model Number of your Floppy. Perhaps I can find a Schematic of it.

    Larry

  9. #19
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    Quote Originally Posted by falter View Post
    So am I understanding that there is a solenoid that should pull the top head down?

    Larry where would I find this shunt?
    You should be able to hear the solenoid when accessing the drive. Listen while accessing A: and then B:. The solenoid will activate on attempting to read, and then when it releases the head load at the end of the disk operation.

  10. #20

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    The control signals are inverted signals. You should be able to ground the select and/or the headload pin to enable the solenoid. I'd still like a picture of the area of the spring. It may not be important but it may show some issue.
    Dwight

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