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Old Mar 28, 2006, 11:57 PM   #1
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I have this old Vivitar 285 that I bought around 1980 (Made in Japan) that I want to use with the Pentax ist DLcamera. I read so much about the damaging power of high trigger voltage of the older flash here. Now I have very little knowledge regarding the use of multi-tester but some nice folk here posted a picture of how to use it to check flash trigger voltage. I followed that and my reading is only 5.8 volt, which is less than most other people's finding. From other posts in this forum and botzilla.com, the old Vivitar 285 suppose to have as high as 350 v rating??

How come my reading is so low? Am I doing it right? Can I trust the meter? Unfortunately I don't have another digital meter to varify the result. (Actually, I tried to measure the flash with an older analog multi-tester but for some reason could not get any reading). Here's how I did mine...


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Old Mar 29, 2006, 1:10 AM   #2
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Meter seems to be in right area, DCV, lead seems to be in right hole...

That voltage fits to what's here for newer "vintages".
http://www.botzilla.com/photo/strobeVolts.html

Second connection might be in such tight place that tip of analog meter's lead might not fit to it.

Check that batteries are in full charge.
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Old Mar 29, 2006, 8:12 AM   #3
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bright eyes wrote:
Quote:
the old Vivitar 285 suppose to have as high as 350 v rating??
The early models

bright eyes wrote:

Quote:
Am I doing it right? Can I trust the meter?
The flash must be ready to fire (flash ready light) and the measurement must not trigger the flash, then you got the right "trigger voltage"

Simply check the meter with a 1,5 Vbattery



bright eyes wrote:
Quote:
(Actually, I tried to measure the flash with an older analog multi-tester but for some reason could not get any reading).
An analog meter have less resistance, for example a 20 kOhm per volt meter, set at 20 volt range will present a resistance of 400 kOhm, this may pull down the voltage reading, or may also trigger the flash at the moment of measurement. Any digital meter would have 10 MOhm input resistance minimum.
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Old Mar 29, 2006, 6:58 PM   #4
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WhenI measured my 285 awhile ago, which is about 15 years old, it measured less than 12 volts. I did use two different meters for the test and the readings were within a fraction of a voltof each other. I also tested my 283, which is older than my 285, and heres the reading on it. The 285 works great with my Panasonic FZ20. The FZ20 has a trigger voltage rating of up to 24 volts. I would never use the 283 with the FZ20 for fear of "frying" the circuits in the camera.
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Old Mar 29, 2006, 10:24 PM   #5
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Thank-you guys, after reading your replys, I feel better that the 285 will be okay for my set-up.

KCan wrote:
Quote:
An analog meter have less resistance, for example a 20 kOhm per volt meter, set at 20 volt range will present a resistance of 400 kOhm, this may pull down the voltage reading, or may also trigger the flash at the moment of measurement. Any digital meter would have 10 MOhm input resistance minimum.
That was exactly what happen when I tried to use the analog meter, instead of giving me a reading, it just triggered the flash. Scared the hack out of me the first time, thought I short circuited the flash.

And John, it was you picture that helped me figured out how to test the flash with the digital multi-tester, thanks again.

-BE
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Old Mar 29, 2006, 11:31 PM   #6
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I would very highly recommend performing this test with a meter which has a 'Peak Hold' setting. The discharge of the flash capacitor is very short, and can create higher voltage pulses than you will measure in steady state.

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Old Mar 30, 2006, 12:46 AM   #7
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I replied too this a long time ago. The 285 is below 10v, but its Doberman-bull terrier brother the 283 is what the prisons used with the electric chair, about 300 volts. Strange people these Japs. Two almost identical flash`s, yet so different.
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Old Apr 5, 2006, 6:15 PM   #8
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Hi,



I have a 285 that I bought in the 1970s and wanted to use it on my new Canon 20D - WITHOUT frying it.

A voltmeter showed the voltage to be below 10 volts. BUT, ...

when I had a friend measure peak and/or spike voltages on an oscilloscope, there was an occasional spike well above 100 volts. I ended up buying a Wein adaptor that protects the camera from spikes.

Bob




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Old Apr 22, 2006, 11:50 AM   #9
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Your friend may well have measured the spike in the secondry of the trigger transformer that is applied to the coil or plate on the tube. If you wish to spend megabucks for a Wein then so be it.
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Old May 22, 2006, 3:28 PM   #10
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I've used my Vivitar 283 with the Kodak DX6490 PC socket with no problems. But I see the max. trigger voltage is 500 !!

Why is the Panasonic FZ20 max. triggeronly 24v ?

I see they recommend using the Panasonic DMW FL28 flash

Seems like you have to be really careful what lights you plug in to these new digital cameras.

Max
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