[Normo]

I can get some older though good electronic flash units, the 5600 or 5800, not sure which. Will it fit on the 645 and will it properly sync and work with the 645n? Thanks Norm

[Dark_Mist]

I can get some older though good electronic flash units, the 5600 or 5800, not sure which. Will it fit on the 645 and will it properly sync and work with the 645n? Thanks Norm

If the flash has a standard hotshoe mount, not the unique Minolta flash mount that they adopted in the 90s it will work in manual mode or 'A' mode. It will not work in TTL mode nor will it auto zoom. If you manually zoom it remember to allow for the different fov of medium format lenses compared to the Minolta's 35mm markings.

My advice would be to buy a Pentax or Pentax dedicated Metz flash from the same era as your camera. They are pretty cheap, will allow TTL (depending on the model), should automatically correct for the difference in fov and will work with Pentax flash cables so you can use them off camera.

[grhazelton]

I would be a good idea to look here: Photo Strobe Trigger Voltages to determine the trigger voltages of the Minolta flashes. While Pentax cameras, even the electronic shutter models, like the 645n, are pretty rugged, some of the older flashes have trigger voltages high enough to fry electronics. I use a Pentax AF400T with my 645n, but be aware that used examples often come with the cord intended for the LX's front panel connectors, not to a hot shoe. See Welcome to Bojidar Dimitrov's Pentax K-Mount Page for a rundown on the various cords. Also the AF400T is large and powerful, and eats its SIX AA cells pretty fast. The external power pack TR is a good idea. BTW, the TR is a high voltage supply, runs on 6 C cells, and is hard to find. Promaster made a compatible flash, I have one and it works fine.

[Normo]

Thank you both for the advice. That's just what I was looking for. Norm