S9252 Servo neatral failure?

[geparent2k]

I had just replaced the s3151 servos on my heli and replaced the cyclic and tail with four 9252. I had everything working good could hover, flew the other day fine, and day after, until today. Was flying around and about 20ft off the ground and it rolled to the left suddenly and IMPACT! ANyway after looking at it one of the servos looked like it lost or forgot where neutral was. When I turn on the radio, then the reciever, all the servo horns are supposed to be horizontal (I have a JR Venture CP OS. 37). But when I powered it on after the crash to check the servos, the servo on the left (can't remeber if it is cyclic servo or pitch servo), anyway power on and the servo horn is pointed straight up. I thought maybe the screw came lose and the horn moved, but it was tight. Can a servos neutral position on a S9252 be moved or changed, or what would cause it. I did push it back the way it was supposed to be before powering on, and it just went straight up again. I have a 7CHP transmitter in PCM mode. The only failsafe I have is on the throttle. I have yet to check the battery on the Triton to see how much I pulled out of it or what the voltage is. It is a 1700mah 4.8V battery. I have another heli, a MX450XS with s3107 servos, another servo doing the same thing, but I can push that one back down and it works for awhile, I do have a replacement for that one though. Any thought would sure be appreciated. Considering the way it came down, it is a tough bird. I thought it would break easily with the plastic frame. Broke blades, bent feathering shaft, and canopy windshield, and tail boom. Thank god.

[WayneBrown]

sounds as if you stripped the gears in the servo. Pay your LHS a visit and buy some.

[BarracudaHockey]

Yep, gears are shot, not unusal when crashing a ccpm bird. Cost about 8 bucks.

[geparent2k]

This happened in midair before it crashed. I checked the battery pack after on the Triton, and only used 133 mah, and volts were 5.45. It is a 1700mah 4.8V pack. When thier is no power to the servo, it moves nice and smooth and free, can't feel any stripped gears. I put the servo were it should be when it powers up and it just goes back to straight up. I was wrong about the servo, it was the aileron and not the cyclic. (long pause)....Ok, I swapped the cyclic and the aileron servos channels 1 and 6, the servo does the same thing, so whatever it is is in the servo it self. I will tear into it tonight and send another post

[markg]

i had the same thing happen once; just started to take it up into a hover, and it decided to roll over on its side and impact from about 4 feet.

servo was not stripped, but it was off a bit like you described.

put it on a hitec hfp10 to exercise it a bit; sometimes it worked, sometimes it would only start if i gave it a little help.

sent it back to hitech; they replaced it, said i had a damaged applifier and motor

the first and last time it wasnt a stripped gear....

[DavidH]

This happened in midair before it crashed. I checked the battery pack after on the Triton, and only used 133 mah, and volts were 5.45. It is a 1700mah 4.8V pack. When thier is no power to the servo, it moves nice and smooth and free, can't feel any stripped gears. I put the servo were it should be when it powers up and it just goes back to straight up. I was wrong about the servo, it was the aileron and not the cyclic. (long pause)....Ok, I swapped the cyclic and the aileron servos channels 1 and 6, the servo does the same thing, so whatever it is is in the servo it self. I will tear into it tonight and send another post

Sounds to me like the pontentioner plate that is located in the output shaft of the servo is broken.

Here is the gear set.
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXD57&P=M
See the plate in the bottom left side of the picture. That plate goes in the bottom of the black output gear. That is what positions the potentioner to let the servo know what position to hold. If it is broken and not turning the pot, the servo will move at random on its own. Even thou the gears feel fine.
The plate use to be available as a separate item. Not sure if it still is thou.

David

[geparent2k]

I did tear into it and found nothing wrong with the gears. I looked at them really closely with an old projection lens. No broken teeth or little pieces on the inside. The piece you described in the previous post was not broken in any way. So I put the servo back together and tried it out. Seems to be working fine, but ordered a new one, and will send off to Futaba for inspection and testing. Thank you all for your suggestions and help. My very first servo problem was with an S3151. I had been using it for the throttle. It was jumping aroung back and forth. Took it apart and found a capacitor had broken off its leads right at the board. Soldered and put epoxy around it to keep it from breaking again. That one worked and had no further problems. Again thank you for all your help.