I recently mentioned that I hooked up an old Suntax flash to my Canon 300D. Although completely manual, I was very happy with the results. I was interested in getting an adapter cable to use the flash off-camera, and while digging around came across warnings regarding using old flashes with new digital cameras. The voltages needed to fire the flashes are far higher than modern devices can support, and you’re in danger of frying your camera. I knew my 300D supports up to 6V, and some googling turned up the voltage of my Suntax 9800A: 68V. I thought this was maybe a typo and meant 6.8, since my camera hadn’t exploded. Then I saw this:
You also need to remember that the Canon Hot Shoe – PC circuit is limited to 6volts. Many third party flashes are much higher then this and require voltage protection, like a Wein Safe Sync. High voltage will fry your shutter over time. The excess voltage is converted to heat.
Bugger. I’ve used the flash a fair bit, and have been rather lucky, it seems. Hopefully there’s no internal damage; it seems to be working fine at the moment, thankfully. I might ask for something compatible for my birthday, though – I like the results too much!