Sync Socket for Sunpak 433D Flash

5 Jul 2009

This is a description of adding an external 3.5mm trigger sync port to the Sunpak flash series that includes the 433D and 383 super. These are hotshoe flashes with auto/manual power control up to a guide number of 36 metres, but most don't have a external sync port for convenient off-camera triggering. Here I show my experiences in adding one.

These flashes can be used with a hotshoe adapter, but that adds extra complexity to the setup with more risk of mechanical or electrical problems. There's adequate room inside, so with a bit of work using a drill and soldering iron, it's not very difficult to add a socket to foot of the flash itself. Some basic electronic circuit soldering skills are required. Fortunately it doesn't require disassembly of the main body of the flash where the high voltage stuff is.

The Sunpak 383 Super does have sync port, but it's a proprietary elongated 2.5mm connector that is difficult to obtain, and isn't compatible with other equipment. This same method can be used to also add an extra commodity 3.5mm (1/8") socket to the 383. The Sunpak 422 and 444 models are similar, but vary somewhat depending on the specific variant. Due to the detachable design of the 444D foot, they tend to be very tight for space inside, and I ended up having to put it in the body of my 444D instead. That was a somewhat more involved job.


The Sunpak 433D can have various different foot designs, depending on the particluar camera system it was designed for. Here I show for the Canon model, although some of the other versions use the same foot structure.

The first job is to remove the foot by undoing the 4 retaining screws. That reveals a fairly spacious foot assembly with just the wires going down to the foot. When re-assembling, if the screws don't easily screw back in, you may need to realign the steel plate they screw into.

There is a space in the moulding for a 2.5mm jack, as in the Sunpak 383, but because of the angle, if you use it, it doesn't leave enough clearance for the plug housing. So instead, it's better to instead just drill the housing on the other side of the unit. The location of the drill hole is fairly critical: it needs to be high enough that the socket housing fits in, but it should also be as low as possible, so as to leave maximum room for the plug on the outside. The front half tends to be better than the back half, so the body of the socket is better clear of the bottom edge of the PCB.


The electrical connection involves finding the wires that connect to the centre pin of the flash, and to the slide contacts at the side of the foot. The centre pin connection (here yellow) goes to the tip of the socket, and the slide (here blue) goes to the ring of the connector.

I have used a socket with a switched connector, which has a 3rd connection that connects to the tip pin when there is no plug inserted. I've wired it the original centre pin on the foot, so that the flash can still be used on a hotshoe, but yet can't be triggered by the pin if there's an external trigger attached, as shown in (b) above. This is to avoid problems with cold-shoes that don't have enough clearance. Alternatively the socket could simply be wired in parallel to the existing yellow and blue connections as in (a).

I also cut the orange and white wires to the go to the other two dedication pins. This is to prevent them conflicting with any other type of dedication pins on a modern hotshoe. Leave the two wires going to the sensor on the front so that the auto modes continue to work.

Disclaimer: Remember if you try following these instructions, you do so at your own risk and I am just describing what I've done. If it breaks your flash or camera, you get to keep both pieces.