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[OM] Old High Voltage Flash Triggers [was] church photos - tripod and f

Subject: [OM] Old High Voltage Flash Triggers [was] church photos - tripod and flash
From: "John A. Lind" <jlind@xxxxxxxxxxxx>
Date: Thu, 04 Apr 2002 13:48:53 -0500
My apologies to the Digest . . .
I am posting this again under a new, appropriate subject for the list archives, as it *is* important information!

How old "old" is, and how new "new" is I do not know for certain. There is also a gray area of time during which flash designs were changed.

"Old" electronic flashes (including some with "electronic eye" auto control, *and* studio strobes) were designed at a time when camera flash triggering was done with a set of mechanical relay contacts. It really didn't matter if the voltage across the hot shoe, or PC cord, was 2 Volts or 600 Volts. Consequently, most of them directly triggered the charging capacitor and the voltage across the hot shoe contacts (center and ground) or the PC cord was 300-600 Volts, with most shoe mounts in the 300-400 Volt range.

Then came the advent of electronics sub-miniaturization, sophisticated metering, electronic shutters, and flash triggering using transistorized electronic switching instead of an electro-mechanical relay. The design of flash units also changed to electronic switching at about 3-10 Volts.

The old high trigger voltage flash units, often found at garage sales and in the bins of used odds 'n ends in camera stores, can destroy the flash trigger circuits (and perhaps more) in electronic cameras. The OM-1 and OM-1n are mechanical with the *only* "electronics" being the metering. Consequently they're OK. I *don't* know about the OM-2 and OM-2n!! I'd bet money the OM-2S and OM-4[T] use electronic switching, and they can be damaged by high voltage flash triggering. It's been safer for me *not* to risk it with those two. (I have some old cameras with electro-mechanical syncs.)

**** Hopefully John H. and/or Clint will comment about them. ****

Among the worst offenders are the ubiquitous Vivitar 283 and 285. They've been in production for eons, there's a Googol of them floating around due to their continued popularity, and there are two look-alike versions of each!! The *old* ones can run as high as 600 Volts. The *new* ones run about 6 Volts. When encountering a used one, I don't know of a method to tell them apart except by turning it on, allowing it to charge until the ready light comes on, and measuring the voltage across the shoe contacts using the 1 kV range on a high impedance voltmeter *first*.

Because there are *so* many of the "old" and the "new" versions of these two Vivitar models around, it is a cause of great confusion with people citing anecdotal evidence" "Yep, got a Viv 285 and it works just fine on my Belchfire 9000 Wonderbrick." Someone else hears this, finds an "old" one at a garage sale for a "Fang" price, slips it into his Belchfire 9000's hot shoe and proceeds to fry his camera (making it, indeed, a Belchfire).

Besides these two Vivitar models, there's a lot of others out there too. Most deceptive can be "closet" flashes that have dwelled on the shelf on someone's closet for the past 25 years and still look brand new. My very small, innocent looking Sunpak Auto 140 fits this description quite well! It's in LN condition and has about 300 Volts across its trigger contacts. I use it with my Rollei 35S and Contax IIIa, but *only* them.

Hope this helps some . . . suggesting you either measure it yourself or have someone you *trust* to know what they're doing measure it for you.

-- John

At 12:32 4/4/02, Bob Gries asked:

The original instruction manual says that it was purchased in 1979 for
about $289 (if I remember correctly).  It is a big potato masher that
can cause blindness if one is too close! ;)  it's the perfect thing for
someone who just uses manual, but I have used its "electronic eye" with
some success.

[snip]

What do you mean about checking the trigger voltages?  And why would
this affect electronic cameras?


Thanks!

Bob


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