After waiting months for the RP Cube and getting one ridiculous excuse after another, I decided this yesterday to try out 316 Photo’s circuit. I liked the simplicity, and the self-biasing to save using a battery. So, I went out to the shop and hit the ‘junkbox’ of parts. Being a long time ham radio operator, and somewhat of a hoarder, I looked over a couple of dead PC motherboards to pick off the parts I needed. Almost everything I needed was there. I did substitute a couple of part values in lieu of a trip to Radio (do they even sell anything radio related anymore?) Shack. 

I discovered a slick little device right after I received my RP JRx’s. This device is a little misleading in it’s description on B&H’s website. It’s a product of Interfit and comes under the listing as STR-116. “Strobies” is another line name for Interfit. In any case, it is slick, because it’s $4.95 for my project box, tripod mount, and hotshoe! Here it is!

The PC to hotshoe connection is at the front and top of the STR-116. The “grid” lines in the hot shoe landing area are drawn on a piece of paper and “glued” temporarily in place.

Here’s a cleaner view of the paper in place. I’ll use this as a template to drill some holes into the upper housing.

You should be able to print the following drawing as a template for the hotshoe. The outside dimensions are .725 X .725. 

Removing the 3 screws on the bottom reveals a small circuit board and the 2 PC connections. Unsolder the printed circuit board to front PC connection. I used a little “solder wick” to suck that excess solder out of there. Be careful, it’s tight working in there, and it gets hot very quickly. Try not to melt the housing, or you’ll wish you ordered another Strobie.

Getting that big lump of solder out will free up the front PC connection. Notice that the insulating plastic stays with the section that came out. Grab yourself a #44 drill (.086 inch ) and run that through the opening to rout that plastic out of the metal sleeve. You will reuse that PC connection as a big grommet later.

Take out the 2 screws holding the circuit board out. Slip the circuit board out, being careful not to break the wire going to the top rail (underside in this shot). That is your ground return to the flash.

I decided to use the following eyelets instead of miniature screws and nuts to build the new quench terminal. I picked them up at a local hobby shop in the “model railroad” section. You are going to need a #53 drill (.059 inch) to get a press fit in the housing.

I got a little carried away with the Dremel tool and drilled all 4 holes. However, it may actually allow the flash unit to sit a little more square on the hotshoe. Although you will see that I only used the quench terminal. Needless to say, this will take a steady hand with the Dremel. If you have a tabletop drill press use it.

One thing I didn’t show was that you will want to solder about an inch of solid wire into the “quench” eyelet before you press it into the housing to prevent melting the plastic. If you did all of the previous steps, you have a good idea of how tight and small the parts are you’ll be using. Follow the schematic and keep your leads as short as possible. You’ll probably use a wireframe hookup something like the rats nest I built. Being basically a “junkbox” project, I used a stereo phone jack and wire off of one of my kids old cheap headsets. Pulled the shielded wire through the grommet, and soldered another anchoring lump. Once the tested homebrew cube worked great, I filled it with RTV to shockproof and seal it up. 

It works perfectly, and took me about 3 serious hours to build it. Good luck!