[littledrawe]

How do I measure the trigger voltage of my Vivitar 285?

[aoeu]

I use a Fluke multimeter. Set it for peak, connect the leads, and fire the flash with the button.

[SOldBear]

I use a Fluke multimeter. Set it for peak, connect the leads, and fire the flash with the button.

Huh?

This is how: Linky.

[demp10]

Turn on the flash and let it charge fully. Then use a volt meter and measure between the pin at the bottom of the shoe (positive) and the metal strips at the side groves of the shoe (negative). Make sure that the range in the volt meter is set high enough (200~300V) for the non "HV" version of the 285 flash (the "HV" is around 6V).

If you short the contacts you will fire the flash and the voltage will drop momentarily to 0.

[Hiroshi]

I just wanted to post here in case someone else has this flash and was looking for information on the trigger voltage. I have 2 modules the std 1d and the pt 2d which is pentax specific. I measured 11.7 volts with the 1d, and 5.7 volts with the pt 2d. I did not expect them to be different but they are. I also measured a pentax version sunpak 433d, the trigger voltage was 7.7 volts.

Additional data on the measurement.

Fluke 8050A meter
Voltage measured on 200v and 1000 volt scale

[Lowell Goudge]

For all those inclined to measure the trigger voltage, I can only give one bit of advise.

Know your meter, and voltage measurement theory!

I say this because not all volt meters are created equal.

Meters have internal resistance, and can load the circuit you are measuring, causing a false reading.

I did a post a long time ago, using my Sunpak Autozoom 3000 flash, and 2 different volt meters.

One volt meter is a relitively new Digital Volt meter with a constant input impedance of 20 Meg Ohms. The other meter was a cheap meter, with a 20K ohm per volt (of full scale) impedance. Changing scales really only changes the resistor in series with the meter movement.

Using the cheap meter, on the 15 volt scale, I measured about 10 Volts, but by moving to the 300 volt scale, I measured 150 volts, and using the digital meter I measured 195 volts.

The meter impedance can lead you to a wrong conclusion. If you are using a cheap meter, start on the highest voltage scale available, since this will present the highest impedance to the flash.

The trigger voltage is measured between the center Large contact of the flash and the side contacts that touch the shoe, with the center button being positive.