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Servo gone wonky!

earthsciteach

Moderator
Moderator
#1
Today was one of those picture perfect summer days. The sky is clear, humidity ridiculously low with temps in the high 70's low 80's. I thought to myself, perfect evening for my Wing Surfer (Bixler under another name). She's been sitting for a few months, so I gave her a good once over which entailed soldering on a new bullet connector and tightening the quick connects on the control rods. Once complete, I stepped out the back door to a picture perfect sunset. Visions of my Surfer reflecting the orange light of the now below the horizon sun filled my head.
At about 3/4 throttle I gave the plane a toss. Immediately she rolled into a gentle right-hand turn that I could not counter. So, I did my best to hold her from rolling over, allowing her to circle back to the ground. Weird. She's never done that before.

I double checked the centering on all of the control surfaces - perfect. Maybe I made the classic mistake of reversed controls - nope. Gave the sticks a wiggle and all appeared well. Hedging my bets, I pushed rudder and aileron trim full left.

I gave her another toss in the air and she climbed out nicely. I made a right turn then a left. The left turn seemed to be a bit delayed and sluggish. Hmm.... I circled back overhead and saw the issue. The left aileron was hanging full down. I thought, "broken clevis?" Then, it went back to center. Hmmm.... Then it went wonky again.

I was able to bring her in for a safe landing. Once back in the house I discovered not a broken clevis but a whacked out servo. Now, I don't think its stripped. It just doesn't seem to be able to decide where center is. I've attached a video of this strange servo. Does anyone have an idea of what has made my servo loose its danged mind and how I might fix it?

 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#3
Hmmm. . . wonder if the pot is going bad in the servo.

Scenario might be this: It'll usually give a good resistance/position reading, but every once in a while, its commanded to "the bad spot", and tells the control circuit it's WAY off when it's really just right. Control board over-corrects and by the time it realizes it's going the wrong way, it's gone a long way. so it swing back to the bad spot and starts over again.

Only way I can think of diagnosing it is disassemble and test *slowly* w/ an ohm meter. Unfortunately, only fix is to scavenge a good controller/pot or full replacement.

Have any spare servos lying around? How 'bout in that pretty new blue plane of yours ;)
 
#13
A 'guy I know' has claimed to repair impaired servos with a baking soda bath... this 'guy I know' also claimed to have repaired a wonky FlySky CT6B with the same method.

Don't ask.
 
#14
I know this post is old and dead but I just got a brand new servo from HK that couldn't decide on center right out of the package. unfortunately I had it installed inside a brand new blunt nose versa when I noticed the problem while setting my throws. had to cut it out and reinstall the new one vertically. now I have to switch out the other side just so the throws match. in the future, all my builds will have exposed servos. mine will live out the rest of it's days as a bomb drop servo.
 
#15
Today was one of those picture perfect summer days. The sky is clear, humidity ridiculously low with temps in the high 70's low 80's. I thought to myself, perfect evening for my Wing Surfer (Bixler under another name). She's been sitting for a few months, so I gave her a good once over which entailed soldering on a new bullet connector and tightening the quick connects on the control rods. Once complete, I stepped out the back door to a picture perfect sunset.
Sounds to me like you have a bad solder join on the servos control board. They be cheap so the fix is a new one. False economy to possibly fix that one only to have it fail again.
 
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