Compur/Synchro Compur triggers flashes twice

Discussion in 'Large Format' started by bart feliciano, Aug 1, 2009.

  1. I was wondering if anyone else has run into this issue?
    I have a 135 Xenotar in a Compur, but when I use a longer shutter speed it triggers my strobe twice.
    I've tested this with both a sync cord and a Pocket Wizard and the behavior is consitent, no problems with flash bulbs though, HA!
    I had this one CLA'ed within the last year or so and the shutter speeds are good though.
    Any info appreciated!
  2. Bart, that's something the CLA should have caught. I had one that was doing that as well, and my repair guy fixed it. I seem to recall it was an adjustment though, and not a bad part.
  3. Basically the flash contacts are touching twice, not once as they should. The flash contacts are usually copper, one connects to the outer ring of a PC connector or one pin of a Bi-post while the other contact connects to the center contact of the PC connector or the other pin of a Bi-post connector. Each end of the contacts should be round and convex with the highest point at the center. The double flash is being caused by 1). the contacts being burned resulting in a segment of the contact that does not make contact as it should and one outer edge contacting before the other, 2). is pitted from arcing resulting in two contact surfaces per contact, or 3). the arm of the contact is mis formed causing the contacts not to mate flush, 3). the actuating arm or pin of the shutter is concave causing the contacts to make two times.
    If the strobe or studio flash you are using has a high voltage on the trigger contacts then this is resulting in an arc at the shutter contacts when firing and burning the contacts. There are buffering devices for flash with high trigger voltages to equipment so that the equipment if not damaged. A trigger voltage higher than 6 volts is considered high and the Compur shutter should be able to handle 12V~15V (volts).
  4. That is good info.
    I think I read somewhere that Pocket Wizards are approximately 3.3 volts. Is this correct?
    It sounds like I need to send off the shutter for repair or adjustment, as well as buy some sort buffer for when I use a sync cord.
    Does anyone have a preferred shutter repair shop?
  5. I personally use Advanced Camera Repair (.com, I think) in Portland, Oregon. I've also heard SK Grimes is good too. They seem to be real experts at LF shutters.

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