Flash Problem

[rwest]

I am using a SunPak 4000AF Flash unit on my 300D. Friday night while shooting a Graduation, it would not fire. The Auto Focus sensor on the front of the flash would light up when you would depress the shutter button half way down, but when you would take a shot, the flash would not fire?
When looking through the viewfinder, you can see the flash icon light up briefly, the fade off? Anyone have any problems like this before?

[robertwgross]

What is the trigger voltage of that flash unit?

---Bob Gross---

[rwest]

I have looked everywhere I know to find this, but I cannot seem to find it. Not in the owners manual that I can see, or on the SunPak site.

[robertwgross]

Take the flash unit and turn it on. Wait until it is ready. Then take a DC voltmeter and place the leads across the cable connector where it would plug into the camera.

If it is Canon EOS-compatible, you will see a DC voltage of 5-6 volts. If it is like a lot of non-compatible flash units, you will see a much higher voltage, like 90-200 volts. In general, the non-compatible flash units will destroy your camera electronics, and that may have already happened.

Further, it is likely not ETTL compatible, which is what your camera wants.

---Bob Gross---

[PhotosGuy]

Maybe you should read these:

How to Check the Trigger Voltage
http://www.botzilla.com/photo/G1strobe.html

Flash Photography with Canon EOS Cameras - Part II.
http://photonotes.org/articles/eos-flash/index2.html#trigger