Does this sound like a bad servo to you?

[Libtekguy]

I went out to fly my Trex 500 today. Just FYI, it has a AR7200BX with DS510M's on the cyclic. Anywho, after I lifted off and switched to stunt mode the heli started rolling left. It wasn't a quick roll, but something like that has never happened before. I went back to normal mode and the it flew like normal. Every time I switched to stunt mode it would want to start rolling left. I landed it, switched throttle hold and with it sitting on the ground I moved the cyclic around and noticed that the Aileron servo was slower than the other two and it sometimes would be a little jittery in it's movements.

Obviously I should replace the servo and see if the problem persists, I just wanted to know if anyone could say with some confidence (given the information I have provided) if it is a bad servo or a FBL controller problem.

[Deet]

actually it sounds like a vibe issue caused by the higher head speed

[Libtekguy]

I've considered that as well, but I've had probably 200+ flights on this heli, and at least 30 or 40 since the last rebuild. Everything is as smooth as butter, spool up and down are smooth with no vibrations when on the ground or in air.

I have the know how to troubleshoot the heli. I only put this thread up to see if anyone else could tell me if the symptoms I've listed are indicators of a servo going out. I've been flying for about 2 years, and I haven't experienced a servo going out yet so I'm not sure what the symptoms are.

I don't have a spare servo to plug in it to test it with. What I think I'm going to do is swap the the two front servos (aileron and pitch) with each other and see if the same servo acts up on the other side as well.

[ddj74]

if it only happens in idle up i agree with deet...vibrations. it happened to me except it rolled right and ended up being bad motor vibrations at high head speeds. replaced motor and flies perfectly now.

[Libtekguy]

I swapped the positions of the aileron and pitch servo, as well as the channels they were plugged into. The same servo as before is acting glitchy. To give you an idea of how glitchy, sometimes I can go from full up collective to full down collective and the bad servo will stay full up for a 1 to 2 seconds before it comes down. Sometimes the servo's movement isn't smooth, but is notchy. Not like a stripped gear notchy, but like the position updates it is receiving are lagged and sporadic. I'm confident it isn't the AR7200BX because I've swapped the channels that the servo is plugged into and the same servo is still malfunctioning.

I'm going to get another servo ordered. I got this set of three DS510Ms on eBay for a hell of a deal, hope I can find one for a reasonable price. I'll report back if this fixes the problem. I did go through the head and tail last night as well and I didn't find anything loose. Right now, I don't think it is vibrations, I've never had this problem in the past 200 flights. I do acknowledge that in those 200 flights something can wear, get loose and cause vibration; however, with the servo acting as funky as it is, I'm thinking I should start there.

[Deet]

then its the servo

replace it

[Libtekguy]

I replaced the servo and the problems went away. No Stripped gears in the old servo, I'll hold on to it for spare gears.