Hi,

I started building my First Quad with PCB version S500 (X) and Flysky TH9X TX & R9B receiver. As a beginner, I picked KK2.1 for FC.

I did the routine of binding TX & RX, flash KK2.1, ACC calibration etc along with other settings and my Quad took-off successfully after first few attempts.
Only after few day and not much of flying at all, it started behaving odd. Means, on throttle it drifts badly and never takes-off.

I checked Receiver test and found values to be at extremes for all channels and beyond reach of Trim.
As Rudder is on extreme, whenever I switch on, FC gets armed.

I changed Receiver, assuming it may be faulty with FS R6B but result is exactly same.

I calibrated Radio using the method of left Trim upwards + right trim leftwards and switching Radio on etc.
I also tried factory reset of KK2.1.

It have been over a month since am struggling but with no result.

What do you think I did wrong or which component is malfunctioning.
I am worried if Radio is the culprit as I am not good at soldering and can't get another one!!

Thanks