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  1. #1
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    Cool How-to: Convert stock Traxxas Thumb switch to 3-position, center off switch

    This is a detailed how-to on making your stock Traxxas thumb switch into a three-position, center off switch (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-->) "Is 'Center off' possible for channel 3 on TQi? (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.

    Just a warning: 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.

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    CLICK ANY PICTURES FOR A LARGER IMAGE
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    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
    - Solder
    - 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.

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    Max of 10 pics per post... continuing on below...
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  2. #2
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    STEP 8 – Reinsert the white thing into the little PCB – make sure you orient it so that the new detent put it on the correct end! (For reference’s sake, it will be the OPPOSITE end of the PCB as the “limiter tab” on the upper switch body – you did take special note of that somewhere, right?  ) You should also put the little metal clips on the metal contacts, and put the black slider block carefully(!) on top of them. Make sure the black slider has the correct orientation (the large rectangle protrusion goes on the side that the limiter tab goes on/will go on). If you get this backwards, your switch will not operately smoothly/correctly once it goes back into the TX body…



    STEP 9 – Almost done! Carefully align the top portion of the switch (make sure the bottom part of the lever that inserts into the black slider is lined up to the middle of the black slider!). Also double check that you have the correct orientation (remember the relation of the limiter tab and the three wire soldering points! Press it back on top of the PCB, and line up the legs with the mounting holes. You may need to use a pair of pliers to give a bit of pressure to push the legs into place – you may also find it helpful to touch the holes with a hot soldering iron as you squeeze the pliers.


    (You may wish to re-connect the TX wires before finalizing the reassembly of the switch, to make sure your new center detent is working properly. To test- connect a servo to channel 3 of your RX, and turn the system on. Flipping the switch will move the servo through its three positions LEFT/CENTER/RIGHT. If your new detent is slightly too far off center (from between the regular detents), you’ll find that the servo will not always center when the switch is put in the middle position. If this is the case, you may be able to modify the white piece again to make it work better, so I’d test it here before soldering the legs back on all the way.)



    STEP 10 – If the switch is working as it should (servo centers correctly…), then add a small ball of solder to each leg to secure the switch firmly onto the main PCB. You should also resolder the wires back from the TX to the board (observing the correct position for each!). Then re-attach the red thumb switch (correct orientation, of course), and finally, insert it back into the body of the TX, and screw the PCB back down. Reattach the back of the TX body, and tighten all 5 screws. Battery case lid back on, and voila! Finished and fully functional three position thumb switch, as below:
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  3. #3
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    Quick video of the final product. Works great!




    I hope someone finds this useful!

    Cheers!
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  4. #4
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    top job
    Guide books aren't part of the packaging.

  5. #5
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    Nice write up. Think I'll have a look at using a center out of one of my on/on/on switches rather than modify the existing one.
    (That is once I get a working TX, my TQi has died completely, won't even power up.)

    Thanks for your time posting this up.

  6. #6
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Awesome... I love it!!
    Great detail and instruction.

    Be sure to keep those pictures available for years to come...
    I imagine this will be a well used thread.
    Whatever it is I just said... I could be wrong.

  7. #7
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    Very cool mod, great ingenuity!

  8. #8
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    Nice write up! I wish my TQi had a thumb switch, so I could mod it
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  9. #9
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    Thanks for comments, guys! My TQ 4-channel radios are now pretty much the bomb... I've got the diffs and hi/lo trans on the regular 3-position flip-switch (chan 4/5), and I have my lights controller on the 3-position thumb switch. Right now it's "lights off"->"Lights flash"->"Lights on steady", but once I get a few more parts, I'll be modding up the light system to be way more awesome...

    Bad news - Killed my 3 channel radio's thumb switch (before doing the write-up) - It was my guinea pig switch and I must have dissembled it nearly a dozen times. It would not have died if I'd had that desoldering braid... (Hence I recommend it in the how to!) It's just the little PCB in the switch that died - I broke it applying to much force trying to open the switch up for the nth time. I guess I'll buy some of those on-on-on switches after all to see if I can replace that part of the switch. Of course, I'm in no hurry for it... so I'll continue to try and lay hands on the on-off-on version which would be better to work with...

    Later!
    Last edited by jolynsbass; 05-28-2012 at 08:42 PM.
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  10. #10
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    Dude, I have spares on/on/on switches. They came as a pack of 5.

    If you want to send me your address on PM, I'll see how much it would cost to send you one or two. If it's only a few bucks, I'll get it done as a thank you for your time on this thread.

  11. #11
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    Thanks, Newth! Very generous of you - pm sent!
    Two Rusty VXLs, M2Ks 18/83 - Tag! You're it!

  12. #12
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    I've sent you a couple of switches today, sorry it's been so long. (Stupid knee!)

    I just thought I'd comment on my feelings on this. I was really keen to have the standard looking switch. After finally getting the mod done (thanks jolynbass for all your help), I've found that the switch was too easily moved by accident. That being the case, I've now reverted to a standard toggle switch located in the top of the slot, where the red rocker switch used to be. This switch sits just above my thumb now when driving. Is a shame because the TX looks much better with the red rocker switch, but function has got to come first I guess.

  13. #13
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    Thanks a bunch for that, Newth!

    I'm fairly certain that the "strength" of the holding position is directly related to the depth and angle of the new detent in the little white plastic piece. The deeper the ball goes, and the more of an angle it must overcome to move to the next position, the more it will "hold" in the center position. You may want to try again, being very precise to have the exact same angles on the new V...

    Note: The picture above is *not* an ideal cut - you can see that one angle is shallower than the other. That was my prototype/first attempt - the only one I took a picture of. My subsequent switch mods had a better angle, and I find that they hold center quite easily; they don't move unless I want them to. Then again, I'm only running lights on my 3rd channel (3 sets for the three positions), and it wouldn't be a big deal if it did get flipped accidentally. Rear steer/winch or other applications, it would be bad to accidentally flip it.

    EDIT:
    I've done a drawing on paper of an ideal cut for the little white piece... I'll post it up once I get a chance to scan it. Newth, if you don't mind trying the mod a second time, once I get the new pic up of an ideal cut, would you mind giving me your impression of it then? I think you'll be very happy with the results. I'll see if I can get it online tonight.
    Last edited by jolynsbass; 06-11-2012 at 11:39 AM.
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  14. #14
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    No probs. I'll have a look at your mod then see what's what.
    I should have said above, I used the centre off switch I found to mod things. Be interesting to see how different it looks.

  15. #15
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    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!)
    Last edited by jolynsbass; 06-11-2012 at 10:22 PM.
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  16. #16
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    I'll check it out & get back to you.

  17. #17
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    could the switch be replaced entirely with a dial of some sort for proportional servo control?

  18. #18
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    It probably could be replaced with a pot.
    Whatever it is I just said... I could be wrong.

  19. #19
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    Quote Originally Posted by Jimmie Neutron View Post
    It probably could be replaced with a pot.
    please give a link, picture or definition. I dont know what a "pot" is. thanks

  20. #20
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    Whatever it is I just said... I could be wrong.

  21. #21
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    That has me intrigued - are you saying that channel 3 would be able to turned into a fully proportional channel by simply putting a pot instead of a switch on there? I was under the impression that there was a software limitation in the radio that prevented it from being anything more than a 3 position channel.

    A fascinating idea, though (and probably best explored on a separate thread.)
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  22. #22
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    there is a separate thread. it is
    (http://traxxas.com/forums/showthread...rating-a-servo).
    check it out. thanks to everyone who is helping.

  23. #23
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    Just updating my thread with the result I got from trying to hook up a pot to the channel 3 - no luck.

    (of course, I might have done something incorrectly, and someone else might be able to get it to work... I'm no expert!)
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  24. #24
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    Quote Originally Posted by jolynsbass View Post
    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!)
    Ok. Cut a long story short, the switch works really well. I managed to get it so that it was nice & stiff in each of the 3 positions. So job well done. Unfortunately, it's still not for me.

    Everything was going great until I tried it with my crawler. After unintentionally moving the rear steering for about the 10th time, I powered it down & went home to break out the soldering iron.
    I think however this is more to do with me not being used to having a switch under my thumb all the time & being to used to gripping the controller. As soon as I returned to a toggle switch in the top of the slot, everything was gravy again.

  25. #25
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    Thanks for the update, Newth! Glad to hear you were able to get a good, solid center position. It would be possible to put a quick "disconnect" switch on your remote, so that the thumb switch is only active if the switch is "on", and if it's in "off", the signal would default to center and thumb positions wouldn't affect it...

    But, if you've already got a working solution, probably best to stick with it.

    For me, it's working great with my light switch. Still need to get to new one installed (so middle position doesn't flash the lights, but just turns 1 set of lights on...), but I just finished up the wiring for it today. I'll be posting a big ol' thread about my mods to my Summit once I finish them...
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  26. #26
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    I had the exact same thoughts about a switch to disable it. In the end, I decided it was just making it too complicated for it's own good.

    Next project, re-wire time on the crawler to make channel 5 a front dig. Probably.

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