Burned out controller of the Lama V4
Due to failure of one of the engines the controller started smoking and smelling very bad, all led's went out and no response to the controls. A controller will not be repaired by Esky. This is a very good excuse to open the controller and look for the burned parts. Maybe the controller could be repaired by myself.
After cleaning the black region with isopropylalcohol, which can not be used for drinking, the fried compoment could be removed. It was obvious that the print had been very hot. Copper came loose from the print. With the burned fet removed, the controller still wouldn't start up: no led was blinking nor burning and current of 1 A was drawn. Using a regulated power supply with limited current is a must for testing the controller. Running a broken controller with a lithiumcell is not recomended. Other components could break also. The capacitor C1, which is just near the 6-pin connector, was broken and responsible for the short circuit. After I removed this capacitor, the controller started up as expected: led flashes and green led stayes on. I tried the other channel with a spare engine. It could be controlled by the remote. I measured the drive of the removed FET with a oscillosscope. The signal comes from the chip with the number 101. It seemed to be in perfect shape. The component seems to be an IRF7413ZBF, an N-logic MOSFET..
This images shows the repaired print with the new component. The small FET has to deal with a lot of current. The fet is pulse-driven so it won't handle a lot of power. Either current is flowing with only a small tension over the FET, or with tension over the FET no current flows. P = U x I: so either U or I is small while the other one is high. The print is the only way to loose heat. I added a lot of tin to improve conductance of heat as much as possible. As the coper is damaged, the tin should add new strength. You can still see the two wires I added temporary to connect the bench power supply. These are removed before assembling.
As the receiver was disassembled I took the opportunity to measure the frequency of the receiver. The Oscilator runs 455 Kc below the transmitter which indicates the intermediatie frequency (IF). A transmitter 900 Kc (twice the MF of 455 Kc) below the frequency could interfer with your own transmitter. I didn't try this out, yet.