*idtDs and old flash

Discussion in 'Digital SLR' started by JD, May 8, 2005.

  1. JD

    JD Guest

    Hi, *istDs-ists, I've been wondering for a long time whether I can use my
    very old Canon 155A flash with my very new *istDs...

    I have sent a few emails to Pentax. I got one answer (from Pentax Canada,
    Pentax USA) and it says:

    "I am not able right now to give you the exact voltage in the hotshoe, but I
    would not recommend you to use the Canon 155A with camera."

    Fair enough, I suppose it's not good for business.

    I've removed the sprockets on the Canon 155A hotshoe except of course for
    the central one.

    I've measured the voltage and fount it to be 5.5V (other people report
    8.2-8.7V, 6.04V, 6.5V...)
    Pentax (Germany) is reported to have said that the maximum-voltage for
    DSLR's *istD + *istDS is 30 Volt Positive in the middle.
    BUNG wrote on 8 May that he was told that the *ist-DS is safe for 480V,
    1.26A max.

    I'm confused. Any feedback welcome.


    JD, May 8, 2005
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  2. Jean-

    No doubt the Pentax answer is correct because they have no knowledge of
    the Canon flash.

    I don't know of an easy way to measure the peak current of your flash
    terminals, but suspect it would be less than the 1.26A value. Flashes
    that use a higher voltage across the terminals, require your camera's
    contacts to discharge a capacitor into the primary of an ignition
    transformer. With only a low voltage to work with, it is probably applied
    to an electronic switch inside the flash. Such a switch would absorb the
    higher voltage and current needed to excite the ignition transformer when
    firing the Xenon flash tube.

    If it were mine, I would go ahead and use it.

    Fred McKenzie, May 9, 2005
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  3. JD

    JD Guest

    Thanks for your encouragement. I went ahead some time before I read your
    advice. I hope there is no damage il the long run.
    JD, May 9, 2005
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