Older Vivitar Flash for new Canon SX10

Not recommended. Older flashes have the full voltage across the hot shoe contact. If that voltage touches one of the dedicated contacts in the hot shoe it will damage the circuit of the camera. 300+ volts does major damage to 6 volt circuits!

To test the flash, measure the voltage between the hot shoe contact and the metal contact on the side of the hot shoe. If the flash is fully charged and you measure 300 volts then the flash should not be used.

Later flashes put a low voltage circuit with a transistor switch in its place to protect cameras.

It's safe according to the list at http://www.botzilla.com/photo/strobeVolts.html

Its trigger voltage is borderline according to this list.

Vivitar Zoom Thrystor 3500 flash with a small integral unit at the base that pulls away. I doubt seeing that the manual was printed in June 1982, I doubt the unit has any value.Try to check HERE.

Or try witn Vivitar 3300 Flash.

Hope helps.

The 550 FD came out before digitals. It is fully dedicated(FD) to a type of film camera. Usually this is noted on the back of the flash. CA or C for Canon, MI or MX for Minolta, Ne or NI for Nikon. If its the Nikon dedicated unit, it should not harm your camera, and will most likely work...as a manual flash. You will lose all the neat flash stuff that the D5000 can do.
I suggest you watch Ebay for a Sunpak PZ-30, PZ-40, or a Sigma 430 or 500. The Sigma EF 500 Super will do pretty much everything the top of the line Nikon Flash does, but you can buy it new for half the price of the Nikon unit. All flashes today are dedicated to a certain group of cameras by a certain manufacturer. For example: Canon EOS film cameras or Minolta manual focus cameras.
I suggest you get rid of the 550FD as it is designed for the pre-Autofocus cameras.
Avoid the Sunpak Auto 30DX, the 333, 383, 433, 444 and the PZ 4000/5000 as well as the MZ flashes. These were not designed for your new digital.
Metz also makes some very nice flashes, but they're kinda pricey.

No. The high trigger voltage in your old unit will damage your D90 for certain.

You need to get a newer flash (US=strobe) designed for digital cameras but don't have to stick to Nikon's overpriced offerings. Metz are excellent and have a high resale value as you can change the dedication model to suit different manufacturers.

go here, they have it

That is true. Older flashes used sync voltages as high as 250V. That much extra juice can quickly fry newer cameras. You can use a Wein Safe-Sync between the camera and the flash to electrically isolate the two.

camera sync terminal wont work with even canon recommended flash.This can be the way to test your camera got damage.

It is the HV version, yes you can just put it in a color mode so the sensor on the front guesses the out put- it isn't ttl so it won't know what the camera is thinking