Ultimate Devo F12E (devof12e-XMS) builds

If have tried all what i can - i was not able to unsolder / resolder the fucking chips - i have 2 damaged Mainboards. I ordered now 2 new for 70 Euro each and try to find out who is able to do this.

My bad was always to unsolder the existing chip .. i have the exeperice that the chinese use a solder which is out of "norm" ...

The used solder is ROHS conform, no lead used. This makes it harder to solder.

Depending on your Tools, the easiest way is to put a lot of new solder on one side of the chips legs, so it touches every single leg on this side. If not all pins are covered you can "wipe" in slow manner over the legs so they warm up even. Then apply some lifting force from the pinless side of the chip and gently! try to lift the heated pins up a bit. The still cold pins on the other chip side will thus bend a little. When you have one side of the legs lifted a little bit it is easy to remove the solder from this side by using solderwick or a desoldering pump or even by the solderingiron alone, always heating the solder, take some away, clean the tip of the iron and again take some solder away until there are no connections to the solderpads.

The other side of the chip goes the same way, but it should get loose pretty fast as it is no longer held in place by the now already loose pinrow on the other chipside.

This way you already apply fresh solder to the pads.

When the chip is removed, go over the solderpads just to get them as "flat" as possible. This helps when installing the new chip.


Pre-tin the legs of the new chip.
Because of the wider new chip body, gently bend its legs closer to its body, check if you bent them enough by placing it over the solderpads. It will be raised a little bit from the mainboard. You could cut the extra length of the pins or leave them as they are. I left them as they are and after installation put some hotglue under the chip to support it a bit. But unless you have the manner to throw your tranmitter on the ground on a regular basis this should not be neccessary as the chip is very lightweight an the soldered pins support it very well.

When the pins fit good, place the new chip on the pads and secure it temporarily with e.g. some tape (you can hold it also in place with some tweezers, if you got a steady hand which I have not...). Now solder one leg of the chip and check if it is still aligned.
If it is ok, solder one pin on the other side of the chip, apply gentle force on top of the chip, the leg should "dip" into the tin on the solderpad.
Once again check the alignment.
If it is OK, solder all the pins to the mainboard by just touching the pin and pad, the applied solder is enough to create the connection in most cases.
Check for solderbridges, if there are some, just heat the spot with the cleaned tip of the iron, normally the solder should find its way to the correct place without bridges.

Good luck for your next try!

Oh Crap, I read about removing the old chip and all was going great but realized after I removed the old chip I had pulled out a tiny piece of the tab on the board. Tried ta add solder but to no avail. Guessing the board is done.....any ideas where I can get a new board or have I just ruined a great transmitter?

Don't loose faith. The flash chip pins are connected straight to the main processor if i remember correctly. You can check where the trace went and solder a wire instead or if some trace is left, scratch away a little bit of the green soldermask to get to the copper trace and solder a wire between it and the flash chip pin. Soldering to the main processor pins is not the easiest task because of the little distance between its pins but it is possible (4in1 module owners need to do this in order to get the forth module-chip select).
First of all you have to find out where the trace of the gone pad went and then prepare for reestablishing this connection.

Thanks so much M8A4X!!!! Will try and follow where it goes. Must confess I am an old fart who loves RC and doesn't understand how all this works (but willing to try) had an idea.....could you solder wires from the original chip in its original untouched position on the board to new chip? In a sense have the two chips running together? Again I dont have a complete grasp on how all this works, just a thought.

I have now some contacts to persons how have more know how than myself with this electronical details.
I had the same idea but i want to install a swich. I have found a person how seems to be able to repair my board - and he write to me thats not a quite good idea even if you switch the VCC +. So i dont follow my first plan. I dont want to have a blue-screen while flying with a 3kg Quad with 50 km/h.

I have ordered 2 new boards - 70 Euro each - and let me see if its possible to repair the boards - if not - i let this thing making by a person with more experience

Hope you will be successful - i was totally down after 2 nights ...

Artus, if I cant fix my board, where did you buy a new one? Quickly looked online but didn't have much luck. Thanks

Which country is your home ?

I have some ideas to help you ...

But it depends where you are at home ...

I am in USA, thanks for reply!!!

USA is not easy to help you direct i think cause i am in Germany

Walkera has in each country an "official dealer" try to find out who it is - i have gone this way a year ago and normaly they are able to help you with a new mainboard.

But - you can try to find someone who is able to repair this board - i have found one via Ebay within 2 hours - i think in your country will be a lot of well educated and helpful persons.



And this person will solder me the new chip on the new boards. I have spent 3 nights - better to let someone with experince and Know-how

If you don't find any person who is able to help you - then we can discuss about how i can help you.

I have seen on the Walkera page that IUAS Seattle is the official support. I heard about - and i think they are able to send you a new mainboard.

@rdowzall:
Connecting the chips "in parallel" is not possible like Artus mentioned correctly. Cutting power to one chip can still result in disturbing signals from and to the chips.
In circuits which use an arrangement like that there is something called "slave select", so the storage chip to/from which should be written/read "knows" that it is now meant to do something with the data comming along the datalines. The other(-s) is/are stopped acting for that time.

With the F12E circuits like they are designed I don't think this is intended to do so because normally the main processor only expects one single chip at the end of the circuit traces.

@Artus: May you give a link or name to your sparepart vendor as it may will be usefull to others (me^^) at some day? (I'm also from germany)
Thank you!

In Germany we have 2 companies which are able to help with Walkera Spareparts
The first "Trade4me" - but the dont answer me an email i have sent them 1 year ago. I had the problem with a lost SMD-Resistor from the transmitter-modul board of the F12E

XCiteRc answered me fast - and delivered me also some parts i need for may 3GD Gimbal. And today i have the information that the new boards are available for me within 3 weeks.

(Only the problem how i can earn 140 Euros for paying they are not able to solve)

Thank you very much, Artus!

Regarding the spare boards price... ouch!
Maybe you can also reroute the lost pads by wire on your damaged boards? It would be worth a try before spending the money on the new boards.