External Flash

Discussion in 'Photography Beginners' Forum' started by DeadEye, Jun 4, 2007.

  1. DeadEye

    DeadEye TPF Supporters Supporting Member

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    I found my Very Old --Vivitar 2800 flash and it still works very well on the old Vivitar 400/SL body. I put it on the Canon xti body but it wont work correctly . Will only flash sometimes like once in 30 shots, do I need to adjust a sync setting or is it to old for the new technoligy?

    Thanks DeadEye
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Do you know the trigger voltage of that flash? I think the XTi may be safe for anything up to 250v, but I'm not sure about that.

    Does it only fire once in 30 shots...or does it only show in in the photos that often?

    What settings are you using on the camera (specifically the shutter speed).

    It may be that the contact doesn't sit well on the Canon camera...make sure it's clean and that it's in the right spot.
     
  3. DeadEye

    DeadEye TPF Supporters Supporting Member

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    Just does not fire very often. Tryed lots of shutter speeds including 1/125.. Voltage measures 145.6 dc volts on the fluke meter. Tryed placement of contact there is only one on bottom center.. It may be the top contact ground.
     
  4. DeadEye

    DeadEye TPF Supporters Supporting Member

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    It seems the problem is that the Vivitar body has dry contacts and works the flash as it should. The contacts close and fire the Thyristor in the flash. On the canon body the switch is closed for to short a period to fire the flash, just a tiny bit to short as it will fire sometimes. I am thinking the canon uses an SCR to do its switch, and the only way I know to lenghten close time is to lengthen pulse width to the gate.That would be a firmware change so I guess Ill get a new flash.

    Thanks All. DeadEye
     
  5. Mike_E

    Mike_E No longer a newbie, moving up!

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    Pssssst--Look for a used Metz!
     

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