Fixed – Inverter Mod for TBS Crossfire and FrSKY QX7, X10S & X12

The current hardware revision of FrSKY QX7, X10S & X12 is not fully compatible with the TBS Crossfire protocol.
If you get constant telemetry warnings or your LUA Script is not working, you might be affected. The reason is a wrong (changed) inverter on the FrSky QX7, X10S & X12 wich can not handle the 400k baudrate of the CRSF protocol.
Your Radio Link to the aircraft is not affected, just the telemetry or LUA Script.

Solution 1: Software fix

You can set the Baudrate to 115200 and your Crossfire Module will work without any issues.
Be aware: The lower baudrate will slow down the CRSF protocol

This workaround will give you a baudrate selection on your X7 menu (main menu, hardare page). If you lower it to 115’200baud instead of using 400’000baud the issue is resolved. Due this workaround and the lower baudrate the latency will increase. The regular update rate for CRSF between OpenTX and Crossfire is 250Hz (4ms). Using the lower baudrate the update rate is reduced to 62.5Hz (16ms). Because of this we recommend to fix it properly in hardware if you have the soldering skills or ask FrSky for support on fixing the hardware.

  1. Download latest Taranis Firmware
  2. copy the firmware onto the SD Card into the „FIRMWARE“ folder
  3. start the Taranis in bootloader mode
  4. flash firmware and select 115200
  5. Go Fly!


Solution 2: Hardware fix

I created the following PCB wich TBS and many online shops now sell. With this mod, you can get the full 400k baudrate for your TBS Crossfire System.
You can get this Inverter via TBS or for example the german FPV Racing Online Store
Warning: Only do the hardware mod if you know what you are doing. To desolder SMD components you need a bit of tact. The components around it can be damaged very easily if you don’t do it correctly. Please make these modifications only on your own responsibility/risk. Neither TBS, FrSky or I can guarantee that the mod works! Thank you!

Please follow the guide below:

Mod for FrSKY Taranis QX7

Falls du versehentlich das Q400 Pad abgerissen hast, habe ich auf meinem Test PCB alle SMD Bauteile entlötet und die Leiterbahn verfolgt und markiert.
Du kannst also Alternativ an den rot markierten Stellen deinen Inverter anlöten. Kratze dazu einfach mit einem Schraubendreher die Lackschicht von der Kupferbahn.

Mod for FrSKY Horus X10S

Thanks Yann Bouloiseau for the photos and information for this mod!

Mod für FrSKY Horus X12

Thanks to stxShadow for the Mod – Thanks to for the photo of the PCB


SMD Part List

If you accidently desoldered some nearby SMD parts, don’t worry. I grabbed an old mainboard, desoldered and measured some parts.
Here is a List of parts:

FrSKY Taranis QX7

  • Q400 9014 Transistor
  • R406 10k Ω
  • R407 10k Ω
  • R402 4,7k Ω
  • R415 54 Ω
  • R413 10k Ω
  • R104 1M Ω
  • R106 10k Ω

FrSKY Horus X10

  • no data available yet (if you have a broken mainboard, please send it to me)

FrSKY Horus X12

  • no data available yet (if you have a broken mainboard, please send it to me)
Wenn dir dieser Artikel gefallen hat und du mich unterstützen möchtest, findest du hier ein paar Möglichkeiten. DANKE!
If you liked this article and would like to support me, here are a few options. THANK YOU!

101 Responses

  1. Chris S sagt:

    You are a lifesaver!

  2. Alex sagt:

    Hi! i have a tararis qx7 accst.Does it need hardware modification or is modification software ok too?

  3. Smail sagt:


    writing in english because maybe somebody else has this problem, too.

    1. I did the mod on my XQ7 and when the Micro TX is installed I hear static/hissing from the speaker. Is this normal?
    2. How can I know if I did the mod correctly? No telemetry warnings, LUA working?

    • Phil sagt:

      Hi Smail,

      1. Noises from the speaker is normal due to the Crossfire specific frequency.
      2. Exactly, if LUA works and you don’t get warnings, its all good!


  4. hi, do you can adding bluetooth module into tbs crossfire lite & TBS Micro tx ?

  5. Jeffrey Forhan sagt:

    Did the mod on my Q X7S and noticed that one of the ICs (U402) was bent and loose when I opened the radio and removed the main board. I was able to solder it back (not easy lol). Every thing works fine. One note, if you are using F.Port and switching to CRSF, when you make the change in the BF configurator, it does NOT revert the serialrx_inverted. That drove me nuts for about 10 minutes when the CRSF nano was bound but no input to BF and no telemetry from FC.

  6. Raffy sagt:

    Hi Phil
    I like to find out, will my R9 Module still work with my qx7 after the TBS telemetry mod without any problems or issues? Does the tbs mod also apply for the qx7s?

    • Phil sagt:

      Hi Raffy,

      you can use the R9 Module without any issues after the mod. qx7s is also affected when it has the old PCB. A fre weeks ago, they started to use a new PCB and it seems that you dont need to mod it anymore (not confirmed yet)


  7. Estevan sagt:

    Hi Phill,

    Great work you do there! Congratulations!

    Do you have the inverter MOD schematics for the New Horus X10S Express?


    • Phil sagt:

      Hi, no still don’t have it. I need a remote to verify and test it. As long as i don’t have one, i cant solve that problem.;)

      I hope you understand!


      • Estevan Bataglia sagt:

        If I send you a picture of the board, do you think you could help me? I was able to find Q1 but it looks like it is rotated 90degree. The yellow wire on your picture goes to 3rd pin of the white 11 way connector. Is that connector the one that goes to the usb small board that connects radio to PC? same board that goes to trainer port? C68 looks identical too..

        Thank you so much

      • Estevan Bataglia sagt:

        Update on the Horus X10S Express. Yesterday I did the mod and everything stopped working. only then I realized I didn’t have the betaflight script installed…. :\. So I installed the Q1 trransistor back and removed the mod circuit. Everything worked great at 400.000 baud.

        I guess FrSky did a hw change on this new version.


  8. Tom sagt:

    Hey Phil!

    Got a little problem here.
    I did the mod and tested successfully while the Tx was still open, but now comes the fun part:
    One of my cats jumped on the table, knocked the Tx over and the still not glued PCB ripped the wire including the Q400 pad off. Yeah, sounds like a cover up for bad solder skills, but i work for an electronics company and this is exactly how it happened. xD

    The trace itself isn’t wide enough to hold a wire and i can’t really follow it’s path, do you know if there’s another point i can grab that signal off?


    • Phil sagt:

      Hi Tom,

      on the one hand, its pretty funny but on the other hand not! Anyway, i desoldered all SMD components from my test PCB and highlighted the trace for you! Anywhere on the red trace, you can solder your inverter to. Just remove the paint from the trace with a screwdriver. I uploaded a picture to this blog post.
      Hope that helps, let me know!


  9. Ryan sagt:

    Hello, I have the Taranis Q X7 ACCESS and my board looks nothing like that. There is nothing on the back and the components on the front are not labeled. Any suggestions?

    • Phil sagt:

      Hey Ryan,

      TBS and me know about that. FrSky just changed their layout of the PCB. Right now, i can’t tell you if it’s working without the inverter mod on the new radios. Could you do me a favour and test it?

      Switch to 400k in OpenTX and plug in your Crossfire TX. If you don’t have telemetry warnings and LUA scripts are working, you don’t need the mod anymore!


      • Patrick sagt:

        Was their any confirmation on whether the x10s acess version needs the mod?

      • Lionel sagt:

        Hi Phil,

        I have the Q X7 ACCESS and a Micro TX crossfire module. I don’t find the 400kHz setting on OpenTX 2.3.9.
        I switched the Crossfire update rate setting to 150Hz (locked) and I don’t have any warnings or errors. The LUA scripts for configuration do work.

        I dont know if this is enough to say that the updated QX7 ACCESS does not need the mod but I don’t have any issues for now.
        If needed, I can do more tests.


  10. Jan sagt:

    Hi Phil, will it affect internal 2,4GHz module or this wiring is only for external bay module (X10S).

  11. Martins sagt:

    Do we need same installation for FrSky QX7 Access version?

    • Phil sagt:

      Hey Martins,

      FrSky just changed their layout of the PCB. Right now, i can’t tell you if it’s working without the inverter mod on the new radios. Could you do me a favour and test it?

      Switch to 400k in OpenTX and plug in your Crossfire TX. If you don’t have telemetry warnings and LUA scripts are working, you don’t need the mod anymore!


  12. Niko sagt:

    Which cable section do you use ? 28AWG ?

  13. Ditto sagt:

    Dear Sir,
    Thanks for this detail Mod!! It Helped much.

    I just got a new Micro Tx and want to mod using that little Converter to my QX7.
    after mod, Do I Have to mod the betaflight CLI setting ? since the default was 100. need to upgrade 150 or something else? please help sir.

    get serial rx

    serial_update_rate_hz = 100 -> the default. since CRSF is fast enough I think this need to be faster than this.
    Allowed range: 100 – 2000

    Best Regards, und Vielen Dank!!

  14. Steve sagt:


    I have the Horus X10S without the Mod and Xfire Lite installed connected to a Xfire micro v2 receiver/eagletree vector on sbus.

    Everything seems fine on 400000 baud.

    How do I know if I really need the Mod done?

  15. Mariusz sagt:


    just to let you know, wires for X10 are the same as for x10s – I just finished soldering and everything is working very well – thanks for the instruction !

  16. Diego sagt:


    I have completed the mod but now I don’t get telemetry when I use the 2.4 FR Sky link with my older quads. Is this normal?

  17. Mike sagt:

    So I did this mod last night and had quite a time doing it. I ended up knocking off r406. Before the mod it would take a long time for the micro tx to show, but when I clicked it I would get the blank screen until I exit, but now it is completely stuck on „waiting for crossfire“. What would you do? I also feel like my Crossfire Micro TX was sent to me used. The box was clearly opened before and the antenna was dirty around the sma connector. I ordered it from amain hobbies because nobody else seemed to have it in stock. At this point I’m ready to return the crossfire and buy a new taranis to start fresh, but I’m curious to know if you have any suggestions!

    • Phil sagt:

      Hi Mike,

      So the crossfire worked before the mod? You have to resolder R406. Its a10k Ω resistor. That could be the problem.
      In my opinion, i would also return the crossfire if its cleary used. Maybe there is also an issue!


  18. Jacques sagt:

    Hi Phil, thanks for all your work in support of the community! would you know if the new generation of x10, the x10 Express has the same ïssue“as the original and requires a hardware mod in order to run crossfire at full speed or if they „fixed“it with this new release?

  19. Ditto sagt:

    Dear Phil…
    Please be informed how to set up crossfire on taranis X7 running OpenTX 2.3.0… I could not find baid rate setting any way….please assist…

    Vielen dank!!!


  20. Ditto sagt:

    Can I use the newest Open Tx 2.2.4 for this mod ?. since in 2.2.3 there’s no baud rate setting.

    Vielen Dank und Tchuss !!!

  21. Martin sagt:

    Stupid Question: If I change the Baud Rate does only telemetry get more latency or telemetry and sbus?
    Who needs 4ms on telemetry?

    • Phil sagt:

      Hi Martin,

      i think you will never notice and increase of latency on the telemetry side (theoretical there should be one, if baudrate is lower). What gets affected is the RC Signal. I recommend using CRSF instead of SBUS, tho!


  22. Stefanos sagt:

    Hi Phil! When soldering of either side of the resistor, do you solder on the GND and 3.3V pads on the board or on the actual resistor (which is implied by the actual lines in your diagram)?

    • Phil sagt:

      Hi Stefanos,

      I think you are talking about the brown capacitor, right? Well, when i did the mod, i soldered to the capacitor. There is a chance you rip that cap off, so i would recommend to use those pads. Before you solder to those pads, measure them to find out if they are really connected to the capacitor.


  23. Lenny sagt:

    Hi Phil,
    so I did everything accordingly, pretty sure I didnt dmg anything, but now when I power up my QX7 it wont get past the „Infinity Spin“ logo and no sound is being played „welcome to openTX“. Did I just break my Taranis? x)

    • Phil sagt:

      Hey Lenny,

      thats weird and should NOT happen. Can you send me some photos on how you soldered it? Check again the soldering. Maybe you unplugged something when putting the remote back together?


  24. Mattia Vadalà sagt:

    Hi, Do you think I need this on my taranis X-lite? Have you a schema for it?

    thank you 🙂

  25. Wimpie van den Berg sagt:

    Hi Phil. Thanks for the awesome instructions. Did my mod yesterday on my QX7. Took me less than half an hour from strip to close and it works perfectly. Thanks again, without your help it would have taken me much longer. Kind Regards. Wimpie

  26. FotoBond sagt:

    Hi Phil.
    I made the change in my Horus 12S (I’m a technician so the welding is my job).
    However despite the BAUD 4K in the menu, the telemetry appears and disappears immediately after 1 second.
    Do you have any idea what it could be?
    Thank you.

  27. Hayden sagt:

    Hi there
    Accidentely resolder R405 on the Qx7 board,
    Any idea what part is this? It’s not on your list.
    Thanks for all you hard work!

  28. George sagt:

    Ηi Phil,
    Thanks for sharing all this with us!
    I have the x10s frsky. Before doing the mod i had RF signal lost and critical alarms. I thought it had to do with the mod so i did it with success as my soldering skills made me do it easily.

    Since then nothing changed with the alarms and poor LQ quality i get.
    Does this has to do with the module, the TX, the mod?

    Any thought would be helpfull.

    Thanks again!

  29. Domenico sagt:

    Hi, i’m wonrdering if i can do this mod without an additional board. let me explain, i have the skill to solder smd so can i remove the old inverter and put the new one directly on the board ? it’s possible ?

  30. dew sagt:

    Hi, how do I know if my qx7 needs the mod? I bought it back in May 2017. When did they start producing the version that is incompatible with crossfire?

  31. Kurt sagt:

    Hat jemand auch das Problem bei der Taranis XD9+ .Der TBS Crossfire Micro Transmitter scheint keine Verbindung zu meiner Taranis X9D+ aufzubauen. Crossfire Meldung „Waiting for crossfire devices…“. Auf dem Display erscheint Running aber no RC Signal.
    Scheint das gleiche Problem wie mit der QX7 zu sein?

    Habe alles versucht, wirklich alles.
    Meine Graupner MX20 funktioniert über das DSC Cable (PPM).

    Bitte um Hilfe.
    Vielen Dank

    • Lenny sagt:

      Weiss nicht genau ob ich das richtig verstanden habe. Aber Ich konnte mein Crossfire Module auch nicht mit dem Receiver binden. Habe dann das Module an den PC angeschlossen und mit dem „TBS Agent X“ (nen Programm von TBS) konnte ich auch den receiver finden. FC habe ich vorher in Betaflight zurückgesetzt.

  32. Stefan sagt:

    Hi Phil,
    great work. Will be any High Speed 7404 inverter works well or there is any special requirement? Thank you for your work for FPV community!

  33. tplanefpv sagt:

    Hi Phil – i was doing the mod, and removed q400 from QX7. while soldering wire onto the pad where q400 previously was, that pad came off. Anything I can do to save this taranis? thanks in advance


    • Phil sagt:

      Hey tplanefpv,

      sorry to hear. You can try to locate the wire which was going to the pad and scratch the silkscreen off now grab a very tiny wire and solder it ontop.

      Hopefully you can repair it, please report back!


      • tplanefpv sagt:

        Think I was able to fix it by scraping some of the green stuff and soldering onto the copper! charging some batts to try this it out!

        Hey, another question – i did the software fix first. But at a slight distance, i would keep getting warnings „telemetry lost/ found “ and „rf signal critical/low“ – was that expected? literally 100 feet away with Baudrate to 115200


  34. dutzi sagt:

    Hey Phil
    I Hope you are able to help me. I just tried to do the Mod on my X12S and in a weak moment desoldered and disapeared R128…
    Do you by any chance now the resistance?
    Thanks in advance and greetings

    • Phil sagt:

      Hey Dutzi,

      sorry to hear, but i cant help you. I dont have one here. Please ask FrSky Customer Support, they share those infos. I organized a broken QX7 Mainboard to measure all resistors and share it with you! When you get the Resistor Value, please share it here!


  35. Radu sagt:

    Hello! Did everything according to the instructions. But that “before”, that “after” setting the mod at 115k CF is working, but with 400k there. Prompt please where to dig? Hardware X10S. Thank you!

  36. Matt Howard sagt:

    Hi, Thanks for fast reply. I am currently soldered the output to the other pad of Q400 and it seems to work however I have not tested out range yet and I am still unable to get into the crossfire lua script. Just stuck on Waiting for crossfire. I will try find the trace and solder to that and hopefully that will fix my lua script aswell. Otherwise I am officially stuck 🙁 Thanks for helping phil

  37. Matt Howard sagt:

    Hi Phil, I recently did the inverter mod however while I was desoldering the old Q400 inverter and the pad came off. Does it matter if I solder the output to one of the other pads that was used on the old Q400?

    • Phil sagt:

      Hi Matt,

      that’s bad to hear. Did the pad come off, where you connect the inverter? If so, you can’t connect it to the other pads.

      Here is the solution. Follow the trace of the lifted pad. With a sharp Skalpell, cratch the silkscreen (green paint) off the trace untill you see the copper. Scatch as much as you can but keep away from other parts. Apply some solder and solder it to the scratched trace.

      Hopefully that will work. Report back if you like!


  38. Jason Baldridge sagt:

    Hi Phil, I am having an issue that I am hoping you can help me on…I installed the chip for the baud rate problem and ever since then my ‚discover sensors‘ feature no longer works, plus when I try to run the crossfire lua, for some reason it just flashes ’searching for crossfire devices‘ but never locks on to anything…I should of tried crossfire before doing the mod to rule out something going wrong, but I didn’t…There is no telemetry working on the TX; no Lua’s, no sensors being detected; do you know what is going on? In the link you will see that my X10S is different than yours; mine has no watch battery on the back and yours does for some reason..?….I really need help getting this resolved; do you know what part Q1 was so that I can order 1 to install to see if that fixes my issue? Any help would be great; thanks!

    • Phil sagt:

      Hey Jason,

      sorry for the late reply. I hope you got it solved. Indeed, it would be better to test the Crossfire before doing the mod. Anyway, how did you configured the LUA Script, FC and all the stuff around the Taranis. There could be manny points where it can fail. I don’t think it has something to do with the inverter Mod (at least you did not desoldered some other parts from the pcb by accident).


  39. Mitch sagt:

    Hi Philipp, thanks for your work. Do you have part schematics so I can make my own mod? I cant find local retailer of your mod.


  40. clifyb sagt:

    Hi Phil, I didn’t realize I had the older QX7 and went ahead and did the mod you listed above and i doesn’t work. I later read the „S“ pin on the lower sPort is not functional on the older QX7 radios so I seem to have disabled sPort on the rear bay port pins too. Can I recover this by wiring the „In“ wire to one of the pads at the Q400 location? Thanks

    • clifyb sagt:

      Update: I recovered from my unneeded Q400 mod on my early QX7 by moving the ‚In‘ wire from the non-functional „S“ pin on the sPort per your official mod; and moving it to the Q400 transistor pad farthest from the „Q400“ label. Now it flashes my Rx’s just fine from the rear bay port pins like the X9 and I’m using the latest part from your cool mod PCB too, so Crossfire works fine too.

  41. Yi Joe sagt:

    hi umm i am new and can i ask you a question? will i hard the q x7 if i remove the part q400 with a hot air gun? will it be too hot?

    • Phil sagt:

      Hi Yi Joe,

      if you are not familiar with hot air desoldering please be carful. Grab an old pcb and practice a little.

      The other way, would be with a tiny soldering tip. First lift the one leg and then heat up both legs together on the other side to remove the component.

      But be careful with all the smd components around the Q400. There is at least one person i know who messed up the board, because the accidentally damaged some other parts on the PCB.


  42. GBaquero sagt:

    The X7S has that problem too?

  43. Jure Peternel sagt:

    Hi, am I missing something: why would I need this mod for use with TBS MicroTX? I have this setup and I’m flying without a problem :/

    How are the errors demonstrated? How can I check if I have a problem? Thanks

    • Phil sagt:

      Hi Jure,

      not all Radios are affected. Some older batches seems to work without the hardware mod (like my Q X7). But the most Q X7 and X10/S have this failure.

      Errors will be constant telemetry warning and crashing LUA Scripts.

      If it works on your Radio, your are very lucky and don’t have to change anything. But be shure you run it on 400k Baudrate. 😉


  44. the_mazur sagt:

    After „Hardware fix“ in menu need back Max bauds to 400000?

  1. 26. November 2017

    […] Vorheriger Beitrag Fixed – Inverter Mod for TBS Crossfire and FrSKY QX7 […]

  2. 2. September 2018

    […] подробно описано – на разные аппы. У меня получилось […]

Schreibe einen Kommentar

Deine E-Mail-Adresse wird nicht veröffentlicht. Erforderliche Felder sind mit * markiert

Diese Website verwendet Akismet, um Spam zu reduzieren. Erfahre mehr darüber, wie deine Kommentardaten verarbeitet werden.