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Thread: Model 4 Gate Array no drive power

  1. #1

    Default Model 4 Gate Array no drive power

    This particular computer is in great shape with a nice case, working well keyboard and a great solid green display.
    After replacing the RIFAs I first tested the unit and it went very well. Then the drives, both of them started acting
    up. I removed the drives and cleaned and lubricated them. Same read issues, except on one boot LDOS the lower
    drive 'bit' and loaded the OS but then failed to read again.
    I replaced all the caps except two small ones in the power supply and I get three +5V, two +12V and one -12v testing
    the main connector on the PS. That seems good to me.
    So I checked the floppy drive cable and found the small plastic divider on the main floppy end pushed down enough the
    cable was not making a good connection with the drive. I made the mistake of testing with a split hard drive cable from
    an old XT and powering on. I heard a small noise and received no display. I checked the motherboard and found nothing
    out of the ordinary, but now I have no power to either floppy drive. The reset and CASS and DISKETTE function but no
    power light to the floppy.

    Any suggestions?

  2. #2
    Join Date
    Mar 2013
    Chaffee, MO


    Perhaps you could BEG Frank to take your Money for Repair.


  3. #3
    Join Date
    Jul 2009
    Central Florida


    Larry are you volunteering me? On a side note I have repaired Model 4's before. Could be a simple problem. Thing is right now I don't really have the space to set up for any testting

  4. #4


    Quote Originally Posted by orlandoave View Post
    I made the mistake of testing with a split hard drive cable from an old XT and powering on.
    Can you elaborate on this? It might help narrow down what happened.

  5. #5
    Join Date
    Jan 2014
    Western North Carolina, USA


    When I think of 'split' cable I think of the cables with a twist for drive select and motor on. The floppy and the hard disk (MFM) versions are rather different.
    Bughlt: Sckmud
    Shut her down Scotty, she's sucking mud again!

  6. #6


    I'm going to work some more with it this weekend and will post some updated and clearer data.
    Not retired just yet, got 2 years to go!

  7. #7


    I've had some Model 4/4Ps with the single power supply have issues with the header on the power supply being worn out. I dont mean the pins and solder on the power supply but the plastic part that plugs in. I had an annoying problem for a few weeks that I chased and chased and it turned out the little fingers that cut the insulation and hold the wire were having issues. Some of those pins are stacked with a few wires. Something to check. Mine was dropping the 5V to the motherboard enough to cause intermittent reboots.

    If you have two power supplies, one is for the motherboard and one is for the drives. I haven't seen that in a Model 4 before though, just Model IIIs. May be something in a converted from cassette version you might find.


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