Problem with hot shoe on Canon XT

Discussion in 'Digital Cameras' started by Peabody, Apr 6, 2011.

  1. Peabody

    Peabody Guest

    I posted earlier about a Vivitar 3500 flash I was given, but have
    uncovered a bigger problem.

    I determined that the voltage on the flash's trigger pin was ok for
    my Canon XT, so this morning I mounted the flash on the camera.
    And it doesn't fire. I bought the camera used, and have never
    mounted anything in the hot shoe before, so it may have been dead
    from the beginning.

    So, in troubleshooting, I've found that:

    The built-in flash pops up and flashes properly.

    When the flash is mounted in the hot shoe, the built-in flash will
    not pop up. That means the little switch in the hot shoe is
    working, and the camera is responding properly.

    When I short the flash center pin to its shell, the flash fires.
    The test button on the flash also works.

    I inserted a popsicle stick on one side of the hot shoe to depress
    the "external flash is present" switch, then tested resistance
    between the center pin and ground. I get infinite resistance
    measuring one way, and a diode drop the other way - I assume this
    is a protection diode of some sort for when the current shuts off.

    I then measured resistance when the shutter is triggered, and see
    nothing on my analog meter. Not a twitch. But, I don't know how
    fast it would be, so I don't know whether it should twitch or not.

    Well, unless there's a camera setting I haven't found to enable
    external flash, it seems my hot shoe isn't operating.

    Anybody have any suggestions on this? I assume it wouldn't be
    worth it to send an XT to Canon for repair, but are there any other
    possibilities, or things I should try?
     
    Peabody, Apr 6, 2011
    #1
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  2. It could be that the contacts which are shorted in the shoe to fire
    the flash aren't shorted completely enough to count as a short for the
    flash. That sometimes happens when old film-era flashes are mounted on
    modern cameras which use semiconductor switches. If so this is a well
    known problem, and you should be able to google up a simple cheap
    circuit which you can build into the flash, or alternatively you may
    be able to find someone selling a specialised rather more expensive
    shoe extension with the circuit built-in.
     
    Chris Malcolm, Apr 6, 2011
    #2
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  3. Peabody

    Peabody Guest

    Chris Malcolm says...
    Yes, that sounds like a possibility.

    It just bothers me that I can't detect any activity on the
    camera's hot shoe center pin when the shutter trips.

    Well, I guess the thing to do is find someone with a genuine
    Canon E-TTL II flash, and see if it works on my camera.

    Thanks very much for the information.
     
    Peabody, Apr 7, 2011
    #3
  4. Peabody

    Peabody Guest

    I got out my breadboard stuff and rigged up a 74LS74 D flip-flop so
    that if the center contact on the hotshoe did anything when the
    shutter was pushed, the flip-flop would change state.

    But nothing changed. So it appears the hotshoe is not functioning.
    Now I need to see if I can get to anything to repair it. It's
    possible the hotshoe assembly is removable, but the circuit is
    probably buried.
     
    Peabody, Apr 7, 2011
    #4
  5. Peabody

    Peabody Guest

    I've confirmed that the hot shoe on my XT isn't working. The
    built-in flash pops up and works fine, but the hot shoe won't
    trigger anything. I called Canon, and they think the hot shoe is
    "burned out."

    Canon wants $190 plus shipping for any repair, but it doesn't make
    sense to spend that kind of money on this camera.

    Does anyone have experience taking this camera apart? I'm pretty
    good at electronics, and was thinking if perhaps the transistor
    that drives the center hot shoe pin could be located and replaced,
    that might fix it. But I have no idea where that transistor might
    be.

    Alternatively, is there an independent repair shop for Canons
    where I could send it in and get it fixed at a lower cost?
     
    Peabody, Apr 16, 2011
    #5
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