Fixing the broken resistor in Tinyhawk 2 mainboard
Updated: Jun 15, 2020
This post is mainly about how i have broken one of the resistors on the mainboard resulting with eratic motor behaviour and how I was able fixe it(finally). "Turtle Mode" should only be used if it is absolutely necessary ! (Learned it the hard way) For lazies; just put a 0402 2K Ohm SMD resistor to the shown place if you broke the exact same one in a crash or your free flying prop damaged it just like mine did.
Soo, yes, as most of us are, I am lazy and of course I will not get up from my coach to pick up the quadcopter that is fallen upside down 2 meters from me. I will use the Turte Mode, push the sticks all arround and try to make it flip on its belly. Bad idea ! Turtle mode channels too much energy to the motors and if any of the props are losened in the crash, the prop will fly away somewhere, kill your ESCs and sometimes if you are "lucky" it will projectile just in the direction of the mainboard which might result with a broken component (wink). Thats what happened in my case anyway. Than your motor will stutter and the drone will be unflyable until you replace the mainboard or spend some time to find the problem and try to solve it.
How I Fixed It First of all I want to say I spent as much money as buying a new board to be able to find the best solution for this fix. I searched all arround the web, emailed Emax but couldnt find any direct answers so i decided to try fixing it myself. At the end I could have bought a new mainboard and be done with it but I guess I am curious how things work and it was a good challence to fix it. After the crash I realised the motor was not spinning properly so I opened the guts of my Tinyhawk 2 and inspected the components. First I checked the connections of the not working motor, they seemed ok. Than i replaced the motors to see if it is gone bad. No problem there, the motor was working fine when soldered to other side of the mainboard. Than I inspected for broken components and found out I was missing a tiny 1mm to 0.5mm sized component. Searched through the web for what it is and litteraly it was the first time I learned what a resistor is and what it does :). I found out the size of the resistor I need was 0402 coded. Than I needed to find the correct one with the proper Ohm value. But the mainboard components layout is all different so it is not like, ah this one has 5 resistors and this exact resistor should be same with this one so it should be this value...
So what I did was to took apart an old broken vape pen (yes I vape) and took out the same sized resistors with a heat gun. I measured the Ohm velues of the resistors in the mainboard of the drone (which show arround 600 and 1000ohms) with a multimeter. I found the best matching one from the Vape pen's resistors which was 1200ohm and soldered it to the Tinyhawk with a huge affort (since its tiny). The motor was spinning now however with quick throttle changes it would just stop responding even in mid flight resulting with a death drop. As a solution, I ordered a cheap 130 Value 2600Pcs Resistor Kit from Amazon and soldered two wires to the empty resistor slot in the Tinyhawk.
Using a breadboard kit I was able to test different valued resistors (I new it would be arround 1200Ohm since the one I tried before has given some hope arround that range) and found out 2K Ohm resistor was working perfectly. I ordered the 0402 2kOhm SMD resistor from Mouser.co.uk (by the way even it says "co.uk" the shipment is made from Texas / US !!!) I soldered the SMD resistor to its place using soldering paste since it was too small and it was a pain in the ass to keep it in place while soldering.
Soldering paste acts like a weak glue for the component until you solder it and its much easier soldering this kind of small parts when compared to convensional solder. And its fixed. Its flying just like new now :)
If you don't have access to soldering paste you can watch this youtube video for soldering small components.
And here is more info if you break resistors in different places in your Tinyhawk 2 mainboard.
I color coded for ease of differentiating. Onboard measurement was;
1000 ohms(+-4) for the green ones (solered). 600 ohms (+-4) for the red ones (soldered).
This does not show the exact values of the resistors.
Once they are soldered to the board the value they reflect change according to the surrounding components. What i used to fix one of the green ones was a 2K(2000) ohm resistor. I am assuming green ones are all 2K and red ones are all 1200 ohm resistors when they are isolated. Even it might be a good starting point for the fix, please approach with caution. My assumption might be not that right. So if you want to buy and try, you can start with getting; 2000 ohms for the green ones.
1200 ohms for the red ones.