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RE: [midatlanticretro] IMSAI 8080

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  • Bill Sudbrink
    ... I would recommend: 1) Photograph the unit, inside and out. 2) Confirm that it still has the original unregulated, linear power supply. If not, stop here
    Message 1 of 61 , Jan 29, 2013
      DanielB wrote:
      > Any recommendations on what I should check before attempting
      > a power up? Any advice would be much appreciated.

      I would recommend:

      1) Photograph the unit, inside and out.
      2) Confirm that it still has the original unregulated, linear
      power supply. If not, stop here and post your findings.
      3) Remove all cards, including the front panel.
      4) Create, if you don't already have one, a "dim bulb variac".
      5) Create, if you don't already have, four "automobile bulb"
      dummy loads.
      6) Attach the dummy loads to the power supply board at the
      locations where the wires run from the PS to the backplane.
      7) When you removed the front panel board, you should have also
      removed the wire connecting the power switch. Short the
      connector with a jumper made from heavy gauge wire.
      8) Plug it in. If the "variac" bulb lights brightly or you
      smell or see smoke, immediately unplug.
      9) Note the condition of your dummy load lights. If unlit,
      you could have a blown fuse or maybe you did not correctly
      connect them. Unplug and check.
      10) If the dummy bulbs are lit, check the DC voltage across each
      bulb.
      11) If the DC voltages seem to be in spec, check for ripple with
      an oscilloscope.

      That should get you started. Once you get to step 11, you have a
      good power supply. Next, start testing the boards, one at a time,
      in the backplane, looking for good regulated power on each board.

      Bill S.
    • DanielB
      Yep, front panel is working good now. One odd thing I have run into is that from the Zapple monitor I can write to the SMB s onboard RAM, but I cannot write to
      Message 61 of 61 , May 14, 2013
        Yep, front panel is working good now. One odd thing I have run into is that from the Zapple monitor I can write to the SMB's onboard RAM, but I cannot write to the RAM on the memory board but I can write to the memory board from the front panel.

        Dan

        --- In midatlanticretro@yahoogroups.com, joshbensadon <no_reply@...> wrote:
        >
        >
        >
        > --- In midatlanticretro@yahoogroups.com, "DanielB" <danlb_2000@> wrote:
        > >
        > > After bad chips I finally got the front panel working, and after a couple bad tantalum caps on the SMB I also got that working. Very exciting when I got the Zapple monitor prompt!
        > >
        > > https://lh6.googleusercontent.com/-uQShOzInDeE/UZFoWnYYpsI/AAAAAAAACII/80vupyb6Psc/w883-h662-no/IMG_3933.JPG
        > >
        >
        >
        > Daniel,
        >
        > That's looking great! Very well done :)
        >
        > Can you now Examine/Deposit via the front panel?
        >
        > :)J
        >
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