Throttle Cut Mod

In this article I'm going to show you how to turn any switch you want into a throttle cut switch. I'll be using the Spektrum DX6i, but any transmitter with throttle cut functionality will work just fine. I did this mod because my local club requires you to have a throttle cut switch, especially if flying electric models, and the switch on the DX6i is a push switch, like the trainer switch on most transmitters, and this simply wouldn't suffice. As soon as you let go of the switch, the throttle is live, and you can't change which switch does what (besides within dual rates/exponential) to move it to a two-position switch. I couldn't find a way to solve the issue with mixing, and I wanted something simple, reversible, and not requiring purchase of a new switch with lots of drilling etc to be done. So I decided to open up the transmitter and see what I could do...

You will need a:
    – Transmitter with throttle cut on unwanted switch (doesn't necessarily have to be computerised)
    – Screwdriver (phillips in my case)
    – Sharp point like hobby knife or very small screwdriver
    – Transmitter case/box (a pillow/cushion will work just as well)

 Step 1

If you have the option to, make sure throttle cut is set to ACT (on) in the settings, not INH (off).

Step 2

Turn off the transmiter and REMOVE THE BATTERIES – you DO NOT want to accidentally short something with the batteries plugged in, EVEN if the transmitter is turned off. This is as crucial as removing props when testing motors, and probably less hassle (depending on the transmitter).

Step 3

Place the transmitter face down on either its packaging, its case, or a soft surface like a bed or pillow. This is to ensure that no gimbals/switches get damaged while working on the transmitter.

Step 4

Unscrew all screws holding transmitter front/back together.

Step 5

Open up the transmitter, being careful not to pull on any wires excessively.

Step 6

Having admired its beauty and complexity ;) locate the current throttle cut switch. 

Step 7

Follow the switch's wires to its connector, and keep a mental note of its location (or take a pic). Remove any glue holding the wires to the transmitter's body so that the wires have plenty of slack.

Step 8

Unplug the connector from the transmitter (note: other switches may be attached to the same connector: be wary of this when pulling on it).

Step 9

Locate the position of the desired throttle cut switch (I used mix, since all of my mixes apply all the time so I don't need to turn them on/off). You can use any unused dual rate switch as well. I don't recommend using the gear/flap switches, unless you're only flying aircraft up to 4-channels.

Step 10

Repeat steps 7/8 with the new throttle cut. If both the old AND the new throttle cut switches have a single connector (i.e. nothing else is connected to the white connector), then simply swap the connectors around by plugging them into the other switch's port. Progress to step 19.

Step 11

Now that you have the connectors to both the old and the new throttle cut switches, it's time to swap the wires around. ***DISCLAIMER I do not know much about how these switches work. I think that flipping the wires in one connector may reverse the switch, like in an ESC, but DO NOT TAKE MY WORD FOR IT. I haven't tried it yet. It may short and therefore ruin the switch and/or part of the transmitter.***

Step 13

Starting with the old throttle cut first, disconnect the lighter wire by putting a knife/small screwdriver underneath the little plastic tab, lifting it, and pulling the wire out. Do not force it - if it's not coming out, then lift the tab up more, being careful not to snap it.

Step 14

Remove the lighter wire from the new throttle cut switch now, in the same way as step 13.

Step 15

With your knife/screwdriver, force the tabs of the empty section of the connector back down, to act as a spring holding the new wire in place.

Step 16

With both lighter wires disconnected, and the tabs pushed back down beyond their neutral point, simply swap around the wires, making sure to put them in with the correct orientation (i.e. not twisted upside down). If you're unsure of which way they go in, then simply look at the way the darker wire is inserted and copy that. If you're still not sure, then push it gently in, and if it doesn't click then try another orientation.

Step 17

Repeat steps 13-16 with the darker wires, ensuring that the two sets of wires aren't twisted annoyingly around eachother.

Step 18

With the wires now swapped around, you can plug the connectors back to where they came from (use the picture you took before, if you took one, to remember where they go).

Step 19

By this stage, the wires should now be swapped around, the throttle cut swich should be plugged into the dual rate or mix port, or whatever switch you chose, and there shouldn't be any loose wires.

Step 20

Now you can carefully put the rear of the transmitter back onto the main body, making sure you don't trap any wires, and tighten down the screws.

Step 21

Plug the batteries back into the transmitter, and turn it on. Don't forget that the old throttle cut switch will have the functionality that the new one had before!

Step 22

Go to the monitor screen (or any screen which shows the current position of the channels) and move the throttle around, and test out the throttle cut switch, making sure the throttle goes BELOW idle when the switch is engaged (imperative if operating gas/glow models)!

Step 23

Test ideally on an electric motor first, WITH PROP(S) REMOVED, and ensure that everything works fine. NOTE when connecting the transmitter and the model, ensure that throttle cut is disengaged i.e. throttle is live. This may sound stupid, but if you don't do this then at 0% throttle the motor will be spinning. This can be adjusted with trims, but then if you connect with throttle cut disengaged next time, there will be a throttle deadband up to about 15%, and that will alter throttle midpoints, and change the throttle's sensitivity. It is always good practice therefore to connect with throttle cut disengaged, then engage once fully connected and bound.

Thanks for reading this article! I hope I was clear enough without rambling on for too long; this is my first article, so I'm not sure how you guys will like it and the format. All comments are welcome. I would gratefully accept suggestions and criticisms.