Zener diode across Vivitar 283 flash for use on D50 ?

Discussion in 'Lighting Equipment' started by scott_schnegelberger, Jul 18, 2007.

  1. Apologies for this question -- I know there's tons of discussion on the
    acceptable voltage on a Nikon D50 hotshoe (250V), and the trigger voltage from a
    Vivitar 283 (varies, depending on build year, location). I've tested the
    trigger voltage with an analog meter, and it hovers right below 250V. However,
    this 283 is practically brand new (discovered it in a box while moving, and I'm
    sure it's only had 4 or 5 flashes ever), and the Wein SafeSync option is
    _expensive_ enough to warrant putting that $$ toward a new flash anyway.

    The shoe on the flash actually comes off with two small screws, and the wires
    into the flash circuitry are right there. So I got to thinking... can't I just
    solder a Zener diode across the terminals to prevent anything more than, say, 6
    volts, from crossing over into the camera hotshoe?

    So on my way home one day, I picked up a pair of 5.1V Zeners from RatShack. On
    the drive from RatShack to the house, I wondered something else, though... will
    the Zener diode across those terminals prevent the charging circuit from ever
    going above the 5.1V rating of the diode?

    My EE skills are a bit rusty, but the flash is free, and at $1.29 for two Zener
    diodes, I'm willing to play with it a bit.

    Has anyone built a circuit internal to the Vivitar 28x flash to keep the trigger
    voltage below the 12V ISO standard? If so, any pointers to a diagram?

    Failing that, anyone want to trade for a pristine Vivitar 283 (made in Japan)?
     
  2. You need a few more components:

    http://repairfaq.cis.upenn.edu/sam/zpaofu1.pdf

    http://repairfaq.cis.upenn.edu/sam/strbfaq.htm#strboazp
     
  3. Excellent... I guess I have some more shopping to do. I'm also thinking this won't fit inside the hotshoe itself (like one or two diodes would), unless I can figure out how to get into the upper shell of the flash unit without breaking it.

    I note in your circuit you've got a 5.6V Zener -- I assume there's nothing wrong with substituting one of the two 5.1V diodes I've already bought, right? I don't think so, but would I need to alter the resistor values (again, correct me -- last time I built a real circuit from scratch was probably twent...er, high sch...er, a long time ago)?
     
  4. I don't think you'd need to change the resistors. The circuit is simply designed to keep the high voltage on the right hand side, flowing through the triac when triggered. The resistors provide a bleed current that causes the capacitor to recharge, which will reset the triac and stop current flow, allowing the flash to recharge.
     

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