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MPI 360k won't read/write

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    #16
    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 9, 2019, 01:15 PM.

    Comment


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

      Larry where would I find this shunt?

      Comment


        #18
        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

        Comment


          #19
          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.

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            #20
            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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              #21
              All of that--I'll also add that on most 5.25" floppy drives, the head-load solenoid was an option and can usually be removed easily if you want traditional 5.25" operation (i.e. your system turns the motor on and off). If you have a system that keeps the motor running all the time, the head-load is a nice feature to reduce wear--but the code has to allow for head settling time. When writing drivers for the early Micropolis drives, I initially made the mistake of not allowing about 15 msec for head "bounce" to die down. Reads worked flawlessly, but every once in awhile, I'd write garbage because the head was still bouncing when the write gate was turned on.

              If you head-load is tied to the motor on signal, there's a built-in delay waiting for the motor to come up to speed that masks the head bounce. But if your system ties head-load to drive select, be very careful to make sure that the driver expects that.
              Last edited by Chuck(G); August 10, 2019, 08:26 AM.

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                #22
                Hoping this picture helps. I don't usually use the forum for pics as it does weird things (like flipping the wrong way) or making things too small to really see.. but here is the area:

                20190810_114120.jpg

                This is a video of it doing a directory. I don't have three hands so I can't show me punching that in, but basically when it starts turning is when I've hit Enter on Dir B. It fails with a General Failure error. If I put some weight on the top head.. it'll read just fine.

                https://youtu.be/vyPrCBEU_Us

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                  #23
                  Perchance, does the CDC 9409 drive match pretty closely with yours? See section 12 for configuration. You'll want the head-load with motor jumper.
                  Last edited by Chuck(G); August 10, 2019, 11:18 AM.

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                    #24
                    I hear a clink but see no movement. Also the right leaf spring looks a little wanky ( don't mess with it now ). I'm wondering if this drive lowers the top head with the door but lifts the bottom head with the head load solenoid. I don't see any actuator for the top head. With the disk out of the way, you should be able to actuate the head load armature with your finger. Don't close the door while doing this as you don't want the heads to touch without a disk in the way. It can damage the heads. The head load usually makes more of a thunk and not a tiny tink.
                    Can we see a similar picture with the disk out of the way, maybe looking in from the right side at a slight angle.
                    Dwight

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                      #25
                      For what it's worth, I'm sitting here with an MPI 54 FH drive (albeit the 100 tpi version) and the HL solenoid is located just forward of the spindle motor. When not actuated, there's an L-shaped sheet metal arm attached to the solenoid armature that pushes up on the head assembly. If someone unfamiliar with servicing these drives tries to remove the solenoid the wrong way or otherwise messes things up, that sheet metal can get bent upwards, so that the head never loads.

                      Instead of pushing down on the head, try pushing down on the solenoid armature. That should provide you with a hint of what to look at. If the bracket clears the head assembly, that is, if it doesn't exert upward force when the armature is depressed, it isn't the head-load mechanism that's fouling you up and you can scratch that off your list.
                      Last edited by Chuck(G); August 10, 2019, 01:48 PM.

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                        #26
                        Here is a couple more pictures:

                        20190811_150541.jpg

                        20190811_150547.jpg

                        20190811_150601.jpg

                        Comment


                          #27
                          What's on the other side of the drive, down just in front of the blue spindle motor?

                          Comment


                            #28
                            Here are pics I hope answer that:

                            20190811_211805.jpg

                            20190811_211801.jpg

                            20190811_211745.jpg

                            Comment


                              #29
                              Ah, that clears things up! You don't have a head-load solenoid!

                              See the bottom closeup near the spindle motor on my drives:
                              mpi_bottom.jpg

                              See the screw and the peg through the holes that in your drive are empty? Those mount the head-load solenoid. I also suspect that the last two contacts on the P4.1 plug (the long one; the contacts nearest the power connector) are empty. On models with head-load, there would be green and black wires connected that go to the HL solenoid.

                              Comment


                                #30
                                So, it would seem that this drive doesn't use a head load relay. It would seem we are looking at a mechanical issue and not a head load solenoid. Since we are not getting a picture of the other end, I have to ask about that coil spring. There should be a tail on the other side of the spring pointing down. Is that tail there? Can you remove the board to take a picture of that part of the drive? It might help to get a good picture if you slide the head assembly forward as well.
                                Dwight

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