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09-17-2014, 10:13 PM   #1
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Thyristor?

I have a k100D and a k10D.
I was recently given a Vivitar 2800 electronic flash. I think it is a thyristor, not TTL. The little info sheet with it doesn't say, nor does it say what the voltage is.
Where can I find out? I don't want to fry my camera. Is there a difference between using in directly on the hot shoe and using it off the camera with a cable that connects to the hot shoe?

09-17-2014, 11:25 PM   #2
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Take a look at this site, and read carefully.

Photo Strobe Trigger Voltages

Hope this helps.

Stay safe and have fun.

Joe.
09-17-2014, 11:29 PM   #3
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Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it! Don't use it!

That's a very old term I haven't heard for 30 years. My first flash (nearly 40 years ago) it was a big deal if it was a Thyristor, it meant that not all the charge was lost if the flash didn't flash on full. Yes you could cook your camera. Don't even use it with a cable. - same disaster.
09-18-2014, 01:22 AM   #4
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The Vivitar 2800 was made from the 1980s into the 2000s, and trigger voltage varied widely over the years. Some of them were dangerously high. I agree with Bob - better safe than sorry with that one. Although the Photo Strobe List suggests that it is the same model as the 2800-D, they are very different flashes. The 'D' in '2800-D' stands for 'Dedicated', with multiple pins on the shoe - the 2800 has only the center pin. The 2800 also usually has a red test button on the rear of the flash above the locking nut.

09-18-2014, 02:17 AM   #5
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You can use it with cactus v4/v5 triggers. They can take high voltage but DON'T use it ON camera.
09-18-2014, 02:21 AM   #6
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There shouldnt be a difference between hotshoe and cable triggering unless the camera was built with two different systems for those.
A thyristor is used to toggle high voltages (flash with up to 300 V in this case) with low voltage circuits that most digital systems like recent cameras use.
Looking at the table promacjoe provided, it is not clear whether the trigger voltage of your flash is dangerous as there are contradicting reports.
09-18-2014, 04:21 AM   #7
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Like everyone said above, I wouldn't stick that on any of my digital cameras. It MIGHT be safe, but then again it could fry your camera, I wouldn't want to risk the chance. I have several old thyristor flashes that I use on remote triggers though and they work just fine that way, I just NEVER connect them to the camera either by hot shoe or cable.
09-18-2014, 04:52 AM   #8
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Use a Wein Safe Sync to reduce the voltage to a safe level. I have one and it works fine with the many old flashes I have.
Wein Safe-Sync Hot Shoe to Hot Shoe (SSHSHS) 990-560 B&H Photo

09-18-2014, 11:00 AM   #9
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Wow, you guys have scared me so much I pulled the dern thing out of my mscl. gear bag lest it contaminate something. I go now on a quest to find a unit I can afford that is guaranteed compatible! Many thanks from me and my cameras' brains!
09-18-2014, 11:14 AM   #10
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If you're looking for a simple, inexpensive manual flash the units by Yongnuo seem to be getting positive feedback. If you want to go used, the Sunpak auto 433D is a venerable option and can be found easily on eBay. I picked on up with the zoom attachment last year for about $15.

Last edited by MD Optofonik; 09-20-2014 at 01:48 PM.
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