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Vivitar 285 flash schematic/info wanted

Discussion in 'Electronic Repair' started by [email protected], Nov 22, 2005.

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    Hey all. I just recently ebay'd up a Vivitar 285 flash to work with my
    Pentax *ist-DS DSLR. I measured the trigger voltage at <8V, so it's more than happy
    working with it. I contacted Pentax awhile back and they told me the deviced used in
    the trigger circuit is rated at 480V, 1.26A

    Anyway, I'm looking to add a few things onto this unit. I'd like to get the
    remote sensor cord, but I'm also thinking of trying to build some other circuitry to
    run a few things. In particular, I'd like to find out if the flash is designed to
    allow external quenching through the sensor plug. I've looked at the guts of the
    sensor, and it appears to be wired as follows:
    1-2 connected internally
    3 n/c
    4 R+
    5 R-
    6 n/c
    The pin numbers are counterclockwise, looking at the *flash* (not sensor),
    starting at the first one from the key (i.e. pin1 is approx 2 o-clock, pin2 is 12
    o-clock, etc). #6 is the center. The resistance between R+ and R- is 24k for 1/16,
    92k for 1/4, 168k for 1/2, and of course open-circuit for full M. The colored modes
    look like they've got a resistor in series with the CdS cell, but I didn't bother to
    measure those. Also, I noted that with the sensor removed, there is no voltage at the
    hotshoe and it won't trigger... probably the pin1-2 jumper in the sensor.

    Does anyone have any more detailed info than this? I'm looking for a
    schematic, post-mortem, or a cable pinout. My ultimate goal would be to build a TTL
    circuit for these units to dedicate them to bodies, or at the very least allow one
    flash to act as automatic master for other slaves.

    Thanks,
    -Cory

    --

    *************************************************************************
    * Cory Papenfuss *
    * Electrical Engineering candidate Ph.D. graduate student *
    * Virginia Polytechnic Institute and State University *
    *************************************************************************
     
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