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Posted by Doug Clifford on January 27, 2002 at 04:47:04:
In Reply to: Vivitar 283 6 volt serial numbers? posted by bill wood on January 26, 2002 at 21:35:26:
: I just learned that early 283's had a high voltage sync problem that could damage sensitive camera circuits. I happen to own 5 vivitar 283's from many years ago. How does one tell if it's a high voltage/low voltage unit? Does anyone know which serial number series these would have?
Bill, you've answered your own question. If those Vivitar 283's were made in the 1980's to the mid 1990's, they are designed with a trigger voltage reported to be as much as 300 volts.
Electronic 35mm SLRs and digital cameras will be damaged when used with a flash with a trigger voltage exceeding 12 volts (6 volts for Canon equipment.) Damage can include the total frying of the camera's electronics or the pitting of internal contacts until the camera eventually fails. For a more detailed explanation of flash trigger voltage, read David Marsh's explanation http://www.acecam.com/message/4631.html (hyperlink below.) David Marsh is owner of Apex Photo Technical Services and past-president of NAPET, the international trade organization for camera repair technicians.
How do four 1.5 volt batteries produce more than 6 volts? A capacitor. All electronic flash units (including ones made today) feed current from the batteries into a capacitor which stores up electricity until it reaches several hundred volts and is fully charged. When the flash is fired, the capacitor discharges and hundreds of volts are released instantaneously. Then the process starts all over again. This is why it is EXTREMELY dangerous to open any electronic flash unit - you can get the shock of your life from four 1.5 volt batteries.
You can test the trigger voltage of your Vivitar 283's with a digital multimeter. Use the test leads to fire the flash by touching one lead to the center pin on the bottom of the Vivitar 283 and the other lead to the metal contact on the side of the flash shoe. Black lead to the side shoe contact, red to the center pin on the bottom. Or you can measure the current by doing the same thing with the PC cord. Modern flash units are designed with circuitry which prevents the high voltage from flowing through the flash shoe or PC cord.
You can continue to use your Vivitar 283 flash safely with products such as the Wein Safe Synch, available from camera stores and distributed by Tiffen/Saunders (http://www.tiffen.com/) - You'll want the model which slips on the camera hot shoe and has a PC socket. Roughly $50. (There's also a Wein Safe Synch model for use with studio strobes and power packs.) See this thread on photo.net for more information. http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=000uWU
Paramount Cords also makes PC cords with voltage protection built-in. See http://www.paramountcords.com/
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