Servo help

[seouleast]

Hello. This is my first post here. How is everyone?

I have a trex 600 and had on Hitec 5645 digital servos. They were ok, but they didn't fit the heli and so I had to cut some of the canopy.
Anyways, I got the 9252's for the collective and have them installed ok. The thing is, when I turn on the Tx and plug in the BEC batt to check the servos, they make a whining stressing sound when the throttle stick is in the low position with the throttle cut on.
When in the mid position, I checked the pitch of the blades and set them to zero, but when I bring the throttle down to check the -pitch, the servos whine up. I have to move the throttle to about 15% to make them stop.
With the cut off, and the stick in low position, the whine isn't there. Only with the cut on and the stick in either high or low.

Thanks for any help!

seouleast