hi friends,
i just make a 30" wing span rc plane . all are done but, i extend the wires for the servo motor. so the voltage drop was occurred ( I think) . so the motor is very hard to run. and also, the command takes more time, delay also occurred. so i wish to plan of give  extra power source for a servo. and first of all i doubted, my problem is possible or not?? sir...... so today i do some experiments for giving power supply methods....
1. using dc-dc buck board
using a 1s battery for the buck board input and adjust the voltage as 5.5 volt for the receiver battery port. the servo works very well. there is only one power supply for the 4 servos and there is no, esc .
2 . using power regulators, but it needs more space . so i rejected it. and also i need to make pcb for the voltage reduction.
i thinking about use a 3s battery 1s cell to be connected to the buck board, but that one cell voltage reduce quickly, thats why am putting extra 1s battery for buck board...
3. I connect 5v power source to the servo cable. And I connect the signal wire to receiver, the motor esc will power up the receiver. but it wont work.

and finally i happy, and choosing buckboard method. and i connect all he setup for the final test. that means, i connect the esc in 3ch and give a extra power supply in battery port, and connect all the servos.
and i wish god my setup work well. but it fails, when i turn on the both power supply, the battery port wires are burned . i shocked sir.. hope well, the receiver doesn't get damage. so i thanks god...
why this happening sir ??
and how can i solve this problem??
if you have any idea please tell me friends..
7904349761 this is  my number friends... ( whats app )

and sorry for i didn't mention tx and rx..
im using fsi6x and fsia6b receiver...

thanks   

waiting for your reply..

and why my servos didnt work, and product issue, quality, not enough power supply , not enough signal??

Hi, I don't think extended servo wires can result drop in voltage or signal lag. But if the connection are poor, it may. Using two power source is possible, if all grounds are common, but it may be risky in case of switching power supply. Better way to use a esc with sufficient bec current. Or if want to use a separate power supply, then don't use the bec of the esc. It can be done by removing the positive terminal of esc, leaving, signal and ground connected with the receiver, and power is supplied from another source to all the servos and the receiver.

i would suggest you stick to normal setup, don't add additional power source for your servo,you are just complicating things and make creating more points of failure.

the following are reason i suspect you are having problems:
1) motor finding hard to spin: calibrate your ESC

2)Does the motor spin easily when no prop is attached?
a)if yes,then that means when you attach the prop the motor is under load hence you might have some loose solder joint on the ESC and motor end so re solder them once again

b)if no, it could again mean solder issue or ESC not calibrated correctly

3) Delay in throttle response : do ESC Calibration

4) Servo not functional:
a) check the polarity of servo connection on receiver end
b) if polarity is correct then it can be possible your BEC not able to provide the required power for the servo to work

to do the servo test dont use servo extensions,just connect servo directly to the receiver.

5) the reason for your cable to burn:
a) wrong polarity can cause servo cable to burn off
b) wrong type of cable used, if you have used jumper cable (used for Arduino etc) then it will definitely burn, they cant handle the power rating.
kindly use the servo extensions for this matter!

after all these checks if your things dont work there is a possibility that these parts are non functional (faulty/dead/damaged)

thanks for reply sir,
now i connect all the ground and tell you sir what happened

thanks for reply sir 
i again check all components are good or not. i will tell you sir
i show a block diagram below, what i done

connection is correct in the block diagram,
but can the buck provide the necessary voltage and current? if it exceeds the Receivers input power rating then you can burn the receiver itself!

yeah, but some guys said  to common all the grounds. will it make my rx well sir ??
why this wont work sir, as i shown below.....

The most simplest circuit I can tell you to do is , make all the connection to the Receiver as usual, and just connect the BEC ( in your case DC-DC converter) to any remaining port of your receiver making sure polarity is correct.

Coming to the image you posted, you need to take ground from the output of the BEC ( in your case DC-DC  converter) and Feed to to input ground of the receiver, the reason is if you don't do this you can have interference in the servo.

ok bro.... today i packed all the components, i will tell you tomorrow bro...

ok bro...

Hi, the drawings you have attached, reveals that, you should first work on the basics of how servo, esc, receiver, power supply etc. works. You can find a number of YouTube video on this. Without a sound knowledge of these, you will be wasting your money and time. Please be careful.

yeah thanks for your advice bro....

Hi, here I am attaching two wiring diagrams of common components used in RC. This may help you.

In the second figure, you do not need a -ve from Esc to Rx as UBEC is already being used as alternate power.

nice explanation bro and thanks a lot 

Hi, it is absolutely necessary to connect the -ve terminal. Signal transmissions need reference. It is basic electronics, not rocket science.