Sunpak auto 455 flash gun

I found this for a Sunpak flash which is similar to the G4500dx:

Reading from the "auto555/G4500DX" Manual, you need to:
1. Slide the Film Selector to desired ISO - (that is the same as your camera ISO used - so, make sure you turn Off the Auto ISO feature if your camera has one).
2. Slide the Mode Selector to "A" (Auto position). This will be Auto Thyristor mode on the flash.
3. Slide the Auto F/stop Selecct Know to desired lens openning - ( so use your camera in Aperture priority mode, more in Manual to prevent changes in the camera aperture value during shooting)
Shoot, and be happy with well exposed pictures by the Auto Thyristor features of the Sunpak 555 flash.
The Sunpak 555 works great with Nikon D50, D70 cameras, as you can synchrinize flash practically at all shutter speeds. Excellent for sunny days to get narrow DOF, yet get any ambient light level contribution as desired.
For other cameras, make sure (watch out for) that Aperture Priority mode does not use shutter faster than the camera max X-sync speed - so Manual camera mode could be a better choice for a novice photographer.
In the manual there is also a list of accessories for various brand cameras, How to use Power Ratio in Manual mode, some advice on using wide lenses, how to care of your 555, and Specification section.
Minimal flash duration is 1/450 at full power, so you can safely use Auto Aperture up to 1/500 sec. Flash duration decreases with lower power setting, or lower auto mode need for poser, and the shortest flash duration is 1/17000th sec.

Before you attach it to your camera you must check the trigger voltage first, never use an old flash unit until you check the trigger voltage with a multimeter, most old flash units have a huge trigger voltage that will damage your camera.
Very simple to check the voltage on that Sunpak 622, turn on your volt meter and set it to about 200 volts DC, turn on your Sunpak flash and apply the RED lead to the bottom contact, apply the Black lead to the side of the hot shoe and look for the ground, usually a small metal piece on the side. Now look at the meter, if it shows a voltage of 6 volts or less then it is safe to use on your camera, if voltage is higher, say 12 volts or more, don't use it. A high trigger voltage will certainly mess up your camera in the long run. Even if it has a safe voltage of 6 volts or less, you will only be able to use that flash in Manual Mode, the newer cameras will not sync or recognize an old flash unit.
I have an old Vivitar flash unit that I can safely use on my Canon XTI because the old vivitar has a trigger voltage of 5 volts, safe for all newer digital cameras.

The voltage across the points when fired is very high on old style flashguns if you try this on a modern digital camera you may fry the electrics in the camera. Get a flash gun that is compatible with your camera Have look at the Yongnuo range.

It's "your call" according to http://www.botzilla.com/photo/strobeVolts.html

You may download a copy of the manual here.

Many flashguns deigned for film cameras - even really expensive ones - will not work with DSLRs.
I have a perfectly good pentax gun that cost me almost £300. It is fanstastic on my TOTR Pentax SLR but will only blat at maximum power on my Pentax DSLR. I had to spend another almost £300 to buy the new gun that will work with all the bells and whistles on my DSLR.
It looks as though Canon work theirs the same way.

Sunpak 622 Auto Pro has 6.5 - 8.0 V trigger voltage.
It should be OK for Nikon D6

Strobe TriggerVoltages

Seems like you may be ok. Google pentax k20d supak 344d compatability.

Seems to work OK with my Nikon D80

becRN,

take the camera to a good camera store and try any in your price range, the manual should state the camera's that are compatible. note that many new model flashes do not work on older camera's.