MX-C402SC Loses Power

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  • graybeard
    Technician

    50+ Posts
    • Feb 2009
    • 76

    #1

    MX-C402SC Loses Power

    Mystery time.....

    We have an MX-C402SC (same as in the title) that loses power as soon as the cover is closed. There is still the green light at the ops panel power switch, but we have to reset the main power switch to get it to come on again. The story starts like this: When duplexing color copies the machine would shut down. A technician went out and replaced the primary transfer belt. Seemed to work, but was soon called in again, but the problem had gotten a little worse. By the fourth call we got to the point where the machine just shut down as soon as the system began to turn. Here's a list of the guesses we have taken to this point:
    1. Primary transfer belt
    2. Fuser
    3. Firmware (probably should have been first, but we got to it at least)
    4. Main drive unit
    5. HDD
    6. Fuser drive unit
    7. Controller
    8. PCU pwb
    9. Power Supply
    10. Right door (took complete door assembly from functional machine)
    11. Both high voltage boards (behind the power supply and mounted to bottom of toner holder assembly)
    12. Motherboard

    We have also completely exchanged the drum and developer units, disconnected the cassettes from the system, disconnected the DF.
    The scanner does its thing normally...lights up and moves as it should.
    If we keep a cover open we can get into test commands and check things individually. The only time we lose power is when we test the primary transfer belt.
    We have used two different transfer belts.
    When it powers down we are always left with the green light on the ops panel power switch, but that will not turn the machine back on.....we are forced to power the main switch off then on.
    The machine is now in our office (thank whatever deity you choose) so we know it's not the customer's power.
    The fax option has been removed while we troubleshoot. There is no data security kit, no finisher.
    We were beginning to think swapping the serial number plate with our functional machine might be a good idea, but these things have a painful unibody construction.

    Can anyone tell me what stupid, simple thing it is we've overlooked?

    Thanks for any help,
    Al
  • drowranger
    Trusted Tech

    100+ Posts
    • Jul 2015
    • 122

    #2
    Re: MX-C402SC Loses Power

    I would check TC pwb spring connections (pg 28 items 3-5 & 8-10) and if you have parts replace TC PWB (pg 28 item 39) and see if the error persists. also try to boot up without or replaced memory & PCL .

    Comment

    • faxman28
      Trusted Tech

      Site Contributor
      250+ Posts
      • Nov 2010
      • 436

      #3
      Re: MX-C402SC Loses Power

      hv power supply, hv contacts, and use kynar powder on the transfer belt, sharp bulletin out on having to powder new transfer belt unit, from your description sounds like copier can't turn transfer belt and has over current condition and shuts down, machine should thro w code . I have seen stranger things, also replace check door interlock switch.

      Comment

      • graybeard
        Technician

        50+ Posts
        • Feb 2009
        • 76

        #4
        Re: MX-C402SC Loses Power

        Thanks for the ideas. We ended up replacing the HL Board (small board behind the PCU board) to get the problem taken care of.
        I appreciate the time y'all took to help me out.

        Comment

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