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Adding a 1/8" (3.5mm) Miniphone Sync Port
to a Speedlight Flash

Sunpak 544 with dual sync ports

I love my flashes, thanks in large part to David Hobby. One of the things that David is constantly promoting is his preference for using 1/8" (3.5mm) miniphone audio cords instead of the older, standard PC-sync cords for syncing flashes. PC jacks are notoriously unreliable as well as ludicrously expensive. Miniphone jacks are both more reliable and dirt cheap. Even better, the Cactus V4 radio triggers that I use come with 1/8" sync ports built in. Unfortunately, none of my flashes have them. One flash (a Sunpak 544) came with a proprietary jack; the other three (Vivitar 283, Canon 430EX flash, and Promaster 5200) could sync through the hot shoe only. When the Sunpak's jack started to flake out on me, I figured it was time to add a miniphone plug to all of my flashes.

I bought a 2-pack of stereo 3.5mm jacks at Radio Shack (274-0249) for $2.99. These jacks require a 1/4" hole to be drilled into the surface where the jack is to be mounted, and require about 3/8" of clearance behind that surface inside the flash. In the case of the Sunpak 544, my plan was to locate the miniphone jack right next to the factory jack and wire the two of them in parallel. For the Promaster 5200 and Vivitar 283, I added a new jack and wired it in parallel with the trigger wires on the hot shoe. The Canon 430EX has no room inside in which to mount a new jack, so it will have to make due with the hot shoe. Michael Bass makes new shoes for Canon flashes that have a miniphone jack already in place, and that seems to be the only way to add such functionality to the 430EX and 580EX Speedlites.

Of course, once you get these spiffy new jacks, you'll want to get some inexpensive 1/8" audio cables to plug into them. Check out these options from All Electronics and Deal Extreme for short cables, or this Y-splitter from Deal Extreme.

Before I begin the instructions, a word about safety. The capacitor that powers a camera flash stores a huge amount of current and dispenses it at hundreds of volts. Once charged, the capacitor will store this electricity for a very long time, even if you turn off the flash and remove the batteries. If you happen to touch the capacitor terminals, you'll experience this first hand. At best, the jolt will really get your attention. At worst, it could cause physical harm or (some claim) even death. If you've got a bad ticker or use a pacemaker, don't go anywhere near the inside of your flash. It's simply not worth the risk. If you're able to pay attention to what you're doing and avoid touching exposed terminals, then read on to find out how to add a sync port to various flashes. It should go without saying that this procedure will void any warranty that may still remain on your flash. I've performed this procedure on my own flashes, and it all worked fine, but I offer no guarantee that you won't screw something up and render your own flash unusable. It happens to the best of us. Proceed at your own risk.

If none of the photos on this page load, email me. I need to go kick my firewall.

Promaster FTD 5200

Promaster 5200 with sync jack

I performed this mod first on my cheapest flash, a Promaster 5200 for which I paid only $4. I figured if something went wrong, I wasn't out much, and my more powerful Sunpak 544 would still be usable.

foot removal The Promaster has a detachable foot that allows the same flash body to be used with different cameras. Interchangeable feet specific to each camera manufacturer can be plugged onto the bottom of the flash. It's a pretty slick setup for 3rd party hot shoe flashes in this age of iTTL/eTTL lighting. I merely removed this foot (press the button on the right side of the flash) and made my mod to it without having to mess with the innards of the flash itself and expose myself to the dangerous capacitors.

top panel removal Next, remove the four screws (two per side) that hold the top panel into the main housing of the foot.

jack sizing view inside Looking inside, you can see the large, empty space on one side of the foot, just below the release button. Remove the two silver screws that hold the IR unit to the bottom of the housing. This will give you more room to work. Just don't forget to allow space for it when positioning your new jack and its wires.

empty hole With the IR unit out of the way, drill a 1/4" hole in the side of the housing through which your jack will stick. I recommend drilling a small pilot hole first, since you don't have a lot of wiggle room on the vertical position of the jack, and a large bit will want to walk.

circuit board screws circuit board screws There are four screws which hold the circuit board to the top panel. Remove them. You'll need to solder your new wires to leads on the other side of the board. When removing the circuit board from the panel, be very careful not to lose any of the springs that connect the terminal bumps to the circuit board. They fall out easily.

terminals circuit board hot shoe wires With the board removed, you can solder your jack to the same terminals as the hot shoe. The tip of the miniphone plug should go to the center pin on the shoe (white wire), and the base (collar) of the plug should go to the rim of the shoe (black wire). It's easiest if you solder your new wires to the terminals on the back of the circuit board. I highly recommend that you use stranded wire for this, not solid. These new wires will bend a lot when you're reassembling the flash. I used solid wire because it's all I had, and I had to resolder broken ends more than once due to the stress I inflicted. Before you reassemble anything, now is a good time to test your soldering by putting an ohmmeter between the hot shoe's center pin and the tip of a miniphone wire, and between the side terminal of the hot shoe and the base of a miniphone wire. You should have connectivity between those two pairs, but no others.

jack in place Now it's time to screw the new jack into the hole in the housing and screw the circuit board back onto the top panel. Reinstall the IR unit into the housing. Before reattaching the top panel to the main housing, you may have to scrape away a little bit of plastic from the housing to provide clearance for the wires as they wrap around the edge of the circuit board. Finally, screw the top panel to the housing and clip the housing back onto the flash.


Sunpak Auto 544

Sunpak Auto 544 with dual jacks

My Sunpak 544 is the flash that really needed this mod, since the factory sync port was starting to flake out on me and sometimes wouldn't fire until I wiggled the plug. Armed with the knowledge of how the Promaster flash worked, I proceeded to dismantle my "potato masher."

arm bracket Figuring out how to disassemble the flash was no easy task. First, you must remove the collar that holds the mounting arm to the vertical flash handle. Disconnect the arm, then loosen the two philips screws enough that the collar will slide off the end of the handle.

head screws Next, point the flash head straight up and rotate it 90 degrees to one side. This will expose two screws on each side of the hinge in the lower section of the flash body. Remove the two screws on the front half of the seam. There's no need to remove the screws in the back half.

handle sticker handle sticker handle sticker Now comes the tricky part. Sunpak has a reputation for hiding screws underneath stickers and labels. On the bottom of the flash handle, around the 1/4-20 screw mount, is a black sticker about 1mm thick. Use a small, sharp blade to pry off this sticker. Under it, you'll find two screws that hold together the two case halves at the bottom of the handle. Try not to bugger up the sticker. In my case, there was still enough adhesive left on it that I didn't have to add any upon reassembly.

case innards case open Finally, use a screwdriver or putty knife to pop apart the clips on either side near the top of the handle. The front and rear case halves will fall apart, and the guts will spill out all over the table. Pay attention to how the parts are positioned inside the housing, expecially the circuit boards inside the upper part of the housing, which you'll need to remove to do your work.

Use a knife or tiny screwdriver to remove the "sync" sticker from around the factory sync jack. This will expose a small nut. Unscrewing this nut will release the factory jack to the inside of the housing.

new hole new hole inside inner ribs You'll notice that there are two ribs that run along the inside of the housing, and the factory jack is positioned between these ribs. If you want to locate the miniphone jack next to the factory jack, you'll need to drill your new 1/4" hole between these ribs (drill a small pilot hole first), then grind away these ribs around the hole to make room for the jack housing.

new jack installed new jack installed new jack wired Now it's time to solder the new miniphone jack in parallel with the old sync jack. The terminals on my new jack matched those on the factory jack. I wired the tip of the new plug to the factory jack's yellow wire, and the base of the new plug to the factory jack's black wire. The clearance inside the flash housing is tighter than you might think, so the orientation at which you solder the wires to the terminals is critical during reassembly. You should match the configuration shown in the "assembled" photo at right, not that shown in the "unassembled" photo. I had to remove and resolder these terminals several times before I had the proper clearance to slide the adjacent circuit boards back into place. Now is a good time to test your new jack with an ohmmeter to ensure that you've got connectivity from a miniphone cable to the terminals of your old sync jack.

dual jacks Reassembly wasn't as straightforward as I'd have liked. There are some slots into which the circuit boards must slide, and they don't like to stay there until the case halves are nearly closed. Be sure that your new wires aren't catching on any circuit board components during reassembly. Don't forget to replace the stickers over your factory sync port and the bottom of the handle.

This section was later reposted on the Prairie Rim Images blog.


Vivitar 283

The Vivitar 283 was the easiest of the three to mod. I'd previously added a box to the front of the flash that contained a dial to continuously vary the power setting of the flash. Read about that here. The terminal which that box used to connect to the flash also contains terminals to fire the flash, and the box itself had plenty of room to add a sync port to one side.

I haven't actually modded my 283 yet, but I expect it to be the easiest of the three. Check back later.

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originally written 1 Nov 2010
Obi-Wan (obiwan@jedi.com)

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