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Tutorial: The Complete 4ch Cactus Trigger Mod Guide

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Hello everyone,

After reading numerous posts on here, and blogs, I decided it was about time I modded my Cactus triggers.

First off, here is a list of everything I bought, and prices. It was all bought from Maplin.co.uk

3.5mm Mono Chas Skt 3 £2.37
2AA Battery Box 3 £1.76
Lead Free Solder 2m 1 £2.49
Rigid PP3 Clip 3 £1.48
Solder Station 1 £9.99

That came to under £20, for everything I needed. So here goes...

(This was the third trigger I had done, and hence I did it fastest, I was in a bit of a rush to get these pics up and sorted too, so excuse the crappy light, its 11pm and there isn't much ambience)


Start off with a tidy desk, the tools I have here are Soldering Iron, Pliers/wire cutters, tweezers, stanley knife and nail cutters for stripping the wire, because i'm cheap)


Take the back, and battery off the trigger


Take the mounting bracket off the trigger, we won't be using this.


Take out the bolt, I found the easiest way to do this was to hit the trigger on the desk until it came out, probably not the best way, but it worked.


Here you can see the triggers internals, we will be removing the PC jack on the top, and replacing it with a 3.5mm mono jack


Take out the two screws on the circuitboard, there is one just below the antenna, and one just above the negative battery terminal. You also have to make sure you cut the wires holding the pc jack to the board, it's also a good idea to de-solder them from the board while we're here.


Put the board to one side, we dont need this yet. Undo the P lockring using pliers at first to loosen it off, then you can just undo it with your fingers


Take out the PC jack, you may need to tap the back of it with something sturdy to get it to move, I used my pliers


Here you can see the tab that connects the hotshoe to the PC jack, so the hotshoe works, I found the best way to remove this was to bend it with pliers, then heat up the solder where it joins the hotshoe, and let it fall off, the hotshoe tab is at a 90º angle and through a slot so you may need to hold the trigger upside down to get it to fall off. I then pushed the two tabs so they're flush with the casing, we dont need them.


I pushed the battery contacts down so that we had a nice base to solder onto. It also means that the 3.5mm jack has a bit more room to fit into the casing.

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Here you can see the tinned contacts, my soldering is very sloppy, but it does the job. I also cut the wires from the PPC clip, but dont throw these off cuts away, we will be using them later.


Feed the wires through the hole where the bracket came out of, you should also strip and tin the wires.


Solder the red wire to the bottom (positive) contact, and the black to the top (negative) contact.


Using the pieces of wire we just cut from the PPC clip solder them into the two holes where we de-soldered the old wires from earlier on, they should go straight in. Then cut them to about 1.5" long, and strip and tin the ends.


Here you can see the red wire soldered to the 3.5mm jack. I just copied the polarity from the PC jack, so the left hand wire, which in this case is red, goes to the outer tab.


Here is the black wire, soldered to the center tab. I found the best way to solder them was tin the wires, then thread them through the small hole in the tab, fold it back on itself, and solder at the hole.


Put the board back into the casing, and screw it in. You must then wriggle the 3.5mm jack through the old PC hole, and screw the locking ring on.


Here is the finished product, you can see why the battery tabs are folded down, it means the 3.5mm jack has a little more room to fit in the case.


Hooray! They all work. Here you can see the 3 LED lights all lit up as a successful shot goes off.


Here they are, the finished article. You can see I'm using 2700 mAh batteries, these should be good enough to run the triggers for a while, but your best bet may be with 1.5v standard alkaline batteries, as NiMH batteries are only 1.2v, and could lead to misfires.

At the moment I havn't connected the battery packs to the reciever in any way, or covered the battery packs. This is because I only bought hook tape, not loop tape, and didnt want to spend lots of money on postage for some more on Maplin, and they're not cased because I don't shoot in the rain. In a few weeks I may move the whole thing into a small plastic case, ditching the Cactus case for good, but for now I'm happy with the mod, and will probably just velcro the battery pack to the back of the case, as it's very sturdy now there's no battery pushing it out.

I've tested these and they're very reliable. I've modified my transmitter with a small length of wire but there are plenty of tutorials on that. I'll probably do a proper job soon, for now it's just coiled on the inside of the Tx.

As you can see, I havn't connected them to a flash YET! This is because I'm waiting for my cords from FlashZebra, they should be here in the next 5-10 days, so as soon as they arrive, I'll put up pics of the working mod.

I hope this tutorial has been useful to some of you. I havn't soldered for over 5 years and I found it easy to pick up the soldering iron and go again, so even if you've never soldered before, with a bit of practise on an old PCB you should be good to go.

If you have any problems, let me know.

All the best, Jon.

(Thanks to kuster for [url="http://jeremykuster.blogspot.com/2007/10/gi-cactus-v2s-modification-tutorial.html"]This[/url] post on his blog, Jacob Gibb for [url="http://www.flickr.com/groups/strobist/discuss/72157600352298821/"]this[/url] thread where he wrote about the 3.5mm jack, Chris Garret at the [url="http://dslrblog.com/gadgetinfinity-ebay-radio-flash-slaves-review"]DSLR Blog[/url] where i found out about these triggers. Last but not least, a huge thanks to DH at [url="http://strobist.blogspot.com/"]Strobist[/url] for the greatest lighting website in the world...)

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Great tut, but If I just wanted to do the AA mod, I just wire the AA batteries to the batery terminal built into the receiver right?

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