Originally posted by Rmpjr7 what is the significance of the extra contacts on the SB-25 not touching the contacts on the hotshoe?
The SB-24/25.... are "dedicated" flashguns, just like the Pentax 540 and 360. Besides the sync (trigger) signal, which is the center pin on the foot, and the ground signal, which is on the side(s) of the foot, there are other pins, normally around the center pin (sync) that transfer data between the flashgun and the camera (e.g. aperture setting, ISO settings, lens information, ....).
The communication protocols are different for each brand/make.
A concern of using a flashgun made of a brand on a camera of a different brand is that the incompatibility of the signals between the flashgun and the camera. In worst case, the camera and/or the flash can be damaged.
The pins for Nikon and the pins for Pentax are at different location. So besides the sync signal and the ground, an SB-25 and a Pentax body don't talk.
I use the SB-25 also for my Canon. The locations of the Nikon pins and of the Canon pins match. So I removed the "dedicated" signal pins on the SB-25 just to be safe:
Here's the foot of the SB-25. You see 4 contacts: one for sync signal (center) and three for other data. There is a locking pin (the small dot just in front of the sync pin) but that is purely mechanical. Two of the four screws needed to be undone have been loosened as in this photo:
Now all four screws have been removed, you can separate the leg from the flash body and pull the connector (at the tip of the screwdriver out):
Now the leg is completely separated from the body. Undo the four screw holding the circuit board and the foot beneath:
Now the foot is off the leg. In the photo below, the sync pin (center) is still attached to the spring. The surrounding 3 springs on the legs are for the data pins. Do not remove these 3 springs. The spring on the foot is for the locking pin. This spring and the locking pin should be removed.
Also remove the 3 pins from the foot. Here the data pins, the locking pin and its spring have been off the foot:
Wrap the locking pin and the springs in electrical tape (here they are in the yellow tape) and put the whole thing back into the cavity of the flash so you'll have them when you need them. Re-attach the foot to the leg:
Attached the leg to the flash body:
Shoot away.