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Old 03-20-2011, 04:59 PM   #1 (permalink)
ChrisH
HF Support
 
Posts: 11,383
 

Join Date: Aug 2007
Default Vibration or shakes? CHECK THIS!

So I have been flying my mCP X pretty much every day for the last week it has been out. As I got more and more flights on it (approaching 60 now), I noticed it was developing a vibration. I thought it was my bladescraped-up main blades, so I shaved the weight off my FFF blades and used those. No difference in flight, but it felt really smooth when spooled up in my hand.

On the bench, I realized that one of the aileron servos was twitching intermittently. I could bump the blade with my finger and the servo would jump back and forth (searching for center) for about 3-5 seconds. I unplugged the elevator servo and plugged it into the aileron port, to see if that was causing the problem. Same deal -- same servo was twitching, so it wasn't that specific port. My boss suggested the potentiometers in the servos being dirty, which I thought was unlikely. It was slow so I figured I'd take it apart and see...

Sure enough, there were black marks (on the silver stripe) on the PCB where the wipers on the servos move across. I used some solvent because it was all I had at the time, but it was recommended that isopropyl alcohol or dedicated pot cleaner be used for a better result. I carefully wiped both the silver strip and the wipers, until they were shiny silver again with no black stripes. At this point I had the heli mostly apart so I did all 3 cyclic servos.

Amazingly, when I went to fly it, it was completely solid with NO vibes or shakes whatsoever! It flies identical to the 3 new mCP X's I checked out yesterday for customers, with crisp cyclic inputs and a smooth collective feel. So in short, if you have a lot of flights and have vibes that you can't track down, try this! I had no idea this would make such a big difference but it did!

Pictures (sorry for so-so photos, only had the iPhone 4 at hand):

Start with this:


Remove the two screws holding the servo to the frame


Pull the servo assembly away and flip it over


Remove the four screws holding the plastic servo frame to the PCB


Carefully pull away the servo frame and flip it over


Clean the silver stripe on the PCB with a q-tip (pot cleaner or alcohol)


Clean the wipers on the servo frame assembly in the same manner


Reassemble and you're ready to fly!
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