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Thread: Getting heads to load using cleaning disc on Mitsubishi M4853 DSDD 5.25" loppy drive

  1. #1
    Join Date
    May 2018
    Location
    Melbourne, Australia
    Posts
    88

    Default Getting heads to load using cleaning disc on Mitsubishi M4853 DSDD 5.25" loppy drive

    Trekked out to the computer shop where I bought my M4853 DSDD drive to pick up a cleaning disc today because prices for these things on ebay are more than I paid for the drive.

    The proprietor and I agreed that it was not feasible to get in there with a cotton bud.

    However I can see that the solenoid does not drop the top head onto the cleaning disc in spite of the head load jumper setting.

    I believe I read in Verbatim's patent for their disposable cleaning disc insert system that there is an an issue with drives detecting that a disc is inserted because the typical cleaning disc 'cookie' is much less opaque than a real floppy.
    I have read that you are supposed to colour in the ring with a texta to make it darker and thereby ensure the drive enters the Ready condition and loads the heads.

    On a DSDD 720K Sorcerer CP/M disc I have four bad sectors according to uBeedisk.

    They are all on the top head (head 1). I would have thought if this old floppy I am trying to image was just starting to fail due to wear and tear the sector errors would be more evenly distributed across side 0 and side 1.

    While the top head could well be misaligned (it is the one that takes a hammering) I would like to give it a clean to ensure that the problems I am having reading sectors on head 1 and not due to dirt on the head.

  2. #2

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    The Manual and schematics state in Section 7.8, that the Index Pulse must be present for a Drive Ready condition.
    I'm pretty sure none of the cleaning floppy's support an Index Pulse. You could probably unplug the Index Sensor
    and inject the proper signal from a Signal Generator to satisfy the hardwares logic, so you could at least clean the
    heads.

    Larry

  3. #3

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    Quote Originally Posted by ldkraemer View Post
    The Manual and schematics state in Section 7.8, that the Index Pulse must be present for a Drive Ready condition.
    I'm pretty sure none of the cleaning floppy's support an Index Pulse. You could probably unplug the Index Sensor
    and inject the proper signal from a Signal Generator to satisfy the hardwares logic, so you could at least clean the
    heads.

    Larry
    A little cleverness with a NE555 timer chip could work.
    Dwight

  4. #4
    Join Date
    Jan 2013
    Location
    Marietta, GA
    Posts
    2,853

    Default

    I don't have time to look up the manual, but I thought those had a jumper or something that would let you tell it to always leave the head load solenoid engaged.

    I've never run in to an issue with a cleaning disk's index not being recognized. Your cleaning disk does have an index hole opening doesn't it?

    Normally you should just try to do something on the machine that would access the disk.

    I have a pair of M4851 360k drives and both have faults with the second head, so I suspect that may be a common problem with Mitsubishi drives.

  5. #5

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    Correction, my brother checked his 5.25" Cleaning Floppy and it does have an Index Hole.

    I'm assuming you are using a Drive select Line which is one of DS{0..3} and the HS jumper is installed (jumpered) location 6B.
    You likely also have H1 jumpered (default) at Location 2L. Plus R2 at location 2L jumpered.

    Can you post a Photo of your current jumpers?

    Larry

  6. #6

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    I wonder if your head load problems would be due to a rubber bumper turning to adhesive goo inside the head load solenoid like I experienced a couple years ago?
    See http://www.vcfed.org/forum/showthrea...ighlight=m4853

    Larry G

  7. #7
    Join Date
    May 2018
    Location
    Melbourne, Australia
    Posts
    88

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    Quote Originally Posted by retrogear View Post
    I wonder if your head load problems would be due to a rubber bumper turning to adhesive goo inside the head load solenoid like I experienced a couple years ago?
    See http://www.vcfed.org/forum/showthrea...ighlight=m4853

    Larry G
    No because the heads load fine with a real disc. Just not with the generic cleaning disc. I bought a higher quality Verbatim Datalife head cleaning disc last night. It has a (patented) C shaped darkened area under the index hole in the envelope to fool the drive into thinking it is reading a (much more opaque) real disk. I will try it out over the weekend and a mate is bringing over his Panasonic drive so I can eliminate alignment as a problem with reading 4 sectors on side 1. Side 0 images perfectly.

  8. #8

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    Your current default Jumpers should be H1 & R2. What if you try this setting for the Cleaning Floppy ONLY?

    H3 & R2 - This should load the head and keep it loaded. It would be worth a try. See attached PNG.



    H1R2.jpg


    Larry

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