Ive got 6 new ESC's to replace the faulty units in my S800. Supposed to be marked for the red led's, but I can't find anything. I'd hate to solder everything in place only to find out the two red units are on arms rotating in the same direction.
Look closely at the LEDs you will see a difference between the green and the red LEDs. I think to remember that the red ones have a very small red dot in the LED that can be seen !
Wait until you get to over 60. The magnification goes up. Just to emphasize with Boris stated, you can see a small red dot on the red leds. Have some fun.
