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Old Jun 24, 2008, 10:46 AM   #11
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That's good news Russell, glad you got it to work OK, and good that you got the official confirmation of the 30 volt figure. I also have an older Vivitar flash Viv273 that has

too high a sync voltage, works fine as a slave though with a cheap optical trigger.... Jack.

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Old Sep 19, 2008, 4:35 PM   #12
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I converted my Vivitar 3700 (with dedicated Pentax Module) to work with my Pentax K100D.

NOTE: I'm not saying that you should do this. So don't sue me. I'm just saying that I tried it and this is what happened.

What I did
1) Although my Vivitar 3700's trigger voltage only measures about 3.9volts, I was afraid to hook it up to my Pentax K100D because the flash's TTL pins make contact with some contacts on my Pentax K100D and since there is voltage going through these TTL pins, I didn't know how this would affect my Pentax K100D. I was afraid it might blow it up! NOTE: I've read that some Vivitars 3700s have a higher trigger so I guess caution is in order.
2) Since my Vivitar 3700's trigger voltage only measured 3.9volts (which is way less than my new Vivitar 285HV which measures 5.9 volts) I decided to figure out how I would modify my Vivitar 3700 so that I felt safer hooking it up to me K100D.
3) I decided I was going to remove the TTL pins from the flash unit so that there was no possible way for them to make contact with my K100D. (Because the K100D doesn't work with TTL anyway. Only this thing called P-TTL?) This actually turned out to be really easy with the 3700.
4) The nice thing about the 3700 is that it's shoe is on a module & the module is really easy to open up.
5) I unscrewed the 4 screws (two on each side) on the module.
6) I slowly and carefully lifted up the plastic cover on the top. You'll find that it is attached to the circuit board by some stiff and probably fragile wires so be careful.
7) There is a circuit board inside held down with three screws. These three screws also hold the hot shoe on the bottom on -- so be careful when you undo these three screws, because once you undo them the shoe will fall off & if you are not careful you will lose all the tiny pieces in side the shoe.
8) Once I got the shoe off, I noticed that the TTL pins are only held in with a spring. The spring pushes the TTL pin down so that it makes contact to the contacts on the camera & the spring conducts the electricity back up to flash. So I removed the TTL pin & spring for both the TTL connectors.
9) Then I put everything back together.
10) So now my 3700 doesn't have any TTL pins.
11) I remeasured the trigger voltage to make sure it still read 3.9volts and then tried it on my K100D & it worked and my K100D is still working.

It's been a couple of days.

After a while I post an update to let you know if my K100D is still working!

Take care,

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Old Jan 3, 2009, 12:30 AM   #13
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(My first post)

I recently acquired a K100D because (a) it was dirt cheap and (b) I have some old pentax lenses and a flash left over from my Pentax ME Super (!). Anyway, being a complete idiot, I plopped my Vivitar 3700 on top and it worked fine. It never even occurred to me that it might not be safe to do.

Of course, it may be that the next time I pull the trigger the whole thing will become a useless lump of silicon, so don't risk your camera based on my say-so. Probably what I'm doing is totally reckless.
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Old Jan 3, 2009, 6:50 AM   #14
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Hello empirebuilder,

It may very well be safe (I measured very low voltages across the TTL pins), but since it was so easy to take the TTL pins out (and they served no purpose with my K100D) I just took them out to be absolutely sure that no voltage was going across.

I also use the Vivitar 3700 on my Nikon this way in AUTO mode.

Take care,

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