My HBK2 has been performing great since I bought it about 2 months ago. I went to fly it yesterday and the rudder servo wouldn't work. I put a new servo on, still not working. I put a new receiver on, still not working. I put a new gyro on, still not working. I changed transmitter , still not working. Have I missed something because everything else seems to be working fine, its just the rudder servo not working.

G'day mate, had a simular prob the second time I flew mine. Everything worked as usual but servo, then I noticed red light on gyro just flashing instead of on. It ended up being the rudder trim on the tx, had it too far from centre so now make sure in the middle when every thing turned on and fixed the problem....hope this helps

Thanks for the reply. As I said before everything works except the rudder servo. The gyro does calibrate but the servo doesn't. It seems there isn't any power getting to the servo but I have changed the receiver. I don't think it would be the esc as the motor works fine. I must be overlooking something simple it seems.

Bypass the gyro. See if your rudder servo even works, plug your servo into the rudder conn on the rx and see if it works if it does not work ...plug any servo into the rudder conn and see if it works, if THAT servo works problem is servo, if not then its somewhere between the rx and tx
I will bet that you have a bad crystal or a bad crystal connection not a bad rx or tx as I had 2 stock esky crystal sets go out on me. On one the throttle could not be controlled (erratic) and on the other the whole thing just "died" First things first if the above did not work remove and reinsert the crystals if that doesnt do it next is to replace the crystals.
DO not buy esky crystals go to a third part at LHS and buy crystals (come in sets)
Usually when a crystal goes bad only some of the functions work or glitch. I nearly replaced both my rx and tx when my first one went out. Fortunatly my LHS (Calif Hobbies) took the time to trouble shoot the system and it only cost me 10$ for new crystals.
BTW I have a tx and rx with new crystals for sale along with 3 used but fairly new esky analog servos with horns as I updated to a dx6i and HS-65 servos and no need for the old system.