How-to: Convert stock Traxxas Thumb switch to 3-position, center off switch
This is a [B]detailed how-to on making your stock Traxxas thumb switch into a three-position, center off switch [/B](from its stock form of a two-position on-on to a three-position on-off-on). This was done by me on 3 different TQ LINK HO 2.4Ghz radios (both 3 and 4 channel), but I believe the instructions should be identical for any version of the Traxxas radios with a thumb switch, from the AM radios to the new TQi radios.
This modification was inspired by the thread conversation held here called (clickable link-->) [url=http://traxxas.com/forums/showthread.php?8951704-Is-Center-off-possible-for-channel-3-on-TQi]"Is 'Center off' possible for channel 3 on TQi? [/url] (which is a somewhat entertaining read all by itself…) In the course of the development of that thread I discovered that instead of replacing the switch mechanism, one could just modify the existing switch for no cost.
[B]Just a warning:[/B] This mod involves some very delicate, small pieces of hardware, which can be easily damaged if treated indelicately… Not for the faint of heart, or the ham-handed! And, perhaps needless to say, you’ll void any warranty that might exist on your radio, so make sure you’re okay with that.
CLICK ANY PICTURES FOR A LARGER IMAGE
Okay, here are the tools you need:
(an asterisk (*) indicates that the tool is not necessarily mandatory, but highly recommended!)
- Soldering Iron (something small, and relatively low wattage, with a fine/pencil style tip. My Walmart 15W iron worked great for this.)
- Fine Philips screwdriver
- Hobby knife
- Desoldering Braid *
- Pliers *
- Fine flat-head screwdriver *
STEP 1) Using the Philips screwdriver, open the case by removing the 5 screws that hold the two halves together. You may want to cut the sticker on the side of the case, if there is one (most do…) A clean slice at the seam will allow easy separation of the halves, and still look good when you put it back together. (You’ll also want to make sure your battery tray lid is off – it can only be secured with the radio in one piece.)
STEP 2) Find the thumb switch PCB. It’ll have two screws that hold it in place (remove these – Philips head screwdriver), along with three wires coming off of the right side. Take note of the order of the colors (top to bottom: yellow, black, purple). You’ll need to desolder them and put them back in the same configuration when done (I wouldn’t use braid for this – just heat the solder and pull the wire out. You’ll use the left over solder to reattach the wires later.) After removing the screws and wires, pull the switch out of the radio – the top screw-hole is usually quite tight, just gently work it free – it’s not glued or anything, just a tight squeeze.
STEP 3) With the switch out of the radio, identify the side with the “limiter” tab… (shown with yellow arrow in pic.) Look at the bottom of the switch, and take note (IMPORTANT) of the relation between the side that the limiter tab is on and which side the three wire spots are on. It is not always the same (I’ve had two radios with the tab on the same side as the wires, and one on the opposite side…) – but you’ll need to be sure to put it back in the same orientation, or your switch will not operate freely when you put it back in the radio. You’ll also want to remove the red switch (just pull it off), making note of how the switch appears, so you can put it back in the same position when done.
p.s. this “limiter” tab is NOT what we need to modify to make a three position switch (though modifying it *does* open up a third position for the switch – that position is unusable with the red thumb switch attached) – so no need to mess with that tab.
STEP 4) Using a fine flathead screwdriver (or other similar tool), peel back the little tabs that attach the top portion/body of the switch to the smaller PCB (shown with yellow arrows). There are two on each side. Just make sure that they are peeled back far enough to clear the PCB when you pull the main switch body off.
STEP 5) Desolder the main legs of the switch (4 of them). I highly recommend using braid for this, as it will remove most of the solder, for ease of putting the switch back in later. Now remove the upper portion of the switch (the little PCB stays where it is). I found that I needed to apply a bit of leverage with a small flathead screwdriver while touching the legs with a hot soldering iron to release the legs the rest of the way. I don’t know if your experience will be the same, but rest assured it IS possible to remove the main body of the switch – I have done it multiple times on multiple radios. It is probably the most difficult part of dissembly. (Again, not for the faint of heart!)
IMPORTANT NOTE: When you pull the switch apart – you’ll be dealing with a few very small and delicate items – be especially careful not to drop/lose the pieces, or damage them through rough handling.
STEP 6) With the switch body off, locate the black plastic block – pull it off of the PCB if it’s still on there… (it might be in the top half of the switch). There are also little metal clips, one on each side – super delicate – don’t mess with them. If they have fallen off during dissembly, just gently put them back on the metal contacts, as in the picture, or in the middle openings of the black plastic block. Your next main objective is to remove the white plastic thing in the middle (shown with a star in the pic) – I found that using a hobby knife to pry it up from the PCB worked best. Just pry up both sides and remove the white thing altogether.
STEP 7) Here’s the main actual mod – Adding another detent, so that the thumb switch stops in the middle. Because of the design of the switch – only two positions are used (remember that limiter tab?). The positions are shown with arrows in the 1st pic. We need to create a new place for the little spring loaded ball at the end of the lever to rest exactly in the middle of the two points. Take a look at the 2nd pic to see what I mean. You’ll need to use a sharp hobby knife to carefully cut this extra detent. If you mess up, you can always have a second shot, by flipping the white thing around and modding the other side (I did that with one of my radios – worked perfectly!) This new detent is your new center off switch position.
IMPORTANT NOTE: The perfect cut would have the “V” of the cut be *exactly* the same distance between the two regular detents, and just wide and deep enough to give good purchase to the little ball as it rotates when the lever flips.
Max of 10 pics per post... continuing on below...
IMPORTANT: Updated Cutting Instructions
Here is a diagram of an ideal cut to the little white thing, for a good solid center detent in your switch:
Notice the following about the diagram:
1) Rotation curve refers to the position of the little metal ball as it pivots on the lever; ball is shown in the three positions, as well.
2) the angles that you cut should be 90 degree angles from the original surfaces, for maximum hold - diagram should explain it.
3) The cut is large enough that the ball "sinks down" into the V. The V itself can extend *past* the anticipated curve line formed by the pivoting of the lever - because of the sharper angle of the V, the ball will not go all the way down, and it's important that the ball goes down into the V about the same distance as with the other lever positions. You can actually pull the little ball off of the spring (magnetic), and test it to see just how far down into your cut the ball extends. Once you've got the perfect cut, put the ball back onto the end of the spring.
This should provide the best holding ability for the center position of the thumb switch. You should be able to flip it with thumb pressure, but not worry about acidentally bumping it into a different position with your thumb.
I hope this helps! (Newth, let me know if you try it - I'm very interested to hear of your results!)