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Heeellllppppp.....

Old 02-06-2007, 07:15 PM
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matt12276
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Default Heeellllppppp.....

Can anyone help me??? So I have just put together a Twist 40, and everything looks and works great. I went to the field last Sunday, and fired her up for her maiden voyage. As soon as the engine started one of the ailerons deflected all the way down and stayed there. I was also getting some twitches from some of the other servos. I have an OS 46FX on this plane that did just come off of a crashed airplane, but I cleaned it up and it fired up on the first try and is running great. The electronics (Futaba receiver and hitec servos) also came out of a crashed airplane (incase that is relevant). When the engine is not running everything is great and it looks like it's ready to fly, but the second I fire up the engine I get the servo activity. Someone at the field told me it may be the bearings in the engine emitting a frequency that is interfering with the receiver, I just have a hard time believing that, but I have no better explanation. I would love to hear if anyone has ever heard of this, if so what is it, and how do I fix it.

Thanks,

Matt
Old 02-06-2007, 07:22 PM
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DavidAgar
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Default RE: Heeellllppppp.....

It could be a vibration that is effecting the reciever. I am thinking that you might want to send it in for a check out. Good Luck, Dave
Old 02-06-2007, 07:33 PM
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Default RE: Heeellllppppp.....

I have had some very similar experiences. Try turning the radio on and pushing on the servos arms with your fingers. I have a Hitec servo that when you push downward directly on the center of the arm, it goes nuts! When I took it apart, I found theat the circuit board has a hair line fracture in it. It also came out of a crashed plane.

Another similar situation after a minor crash: Everything worked fine when the plane was sitting idle. As soon as the engine was started, all of the servos were jittering like crazy. I replaced the receiver and all was well. When I finally disassembled the Rx., I found a hairline crack in the board. I could not see it with a naked eye. It wasn't until I looked with a 10x magnifying loop that I could see the crack!
Doug
Old 02-06-2007, 07:47 PM
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speed lover
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Default RE: Heeellllppppp.....

I had the exact same problem but it was happining with the throttle I fired up my mds 58 and it just went bang straight to full throttle some times it would work but it was delayed and it would also twich like hell and being an mds it was very responsive to the slightest throttle change but that was the only hitech servo I had on it and the rest were futabas so I took it out and and cleaned the small plate inside and it was better but still not reliable I think I changed it over to the rudder and it was ok but I just took it out any way and put a futaba in no problems since I had a metal rod for the throttle that could have been something to do with it I would get some other servos try them if it does not work try to get a shot of a reciever at the field and try the new servos with that I think one or the other will work good luck
Old 02-06-2007, 08:52 PM
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Default RE: Heeellllppppp.....

If you have other twitching, I would be that your receiver is bad from the crash. Maybe a cracked board, and the vibration of the engine running aggrivates it and makes your servos go crazy. Do not even think about flying it until it is resolved.
Old 02-07-2007, 01:27 AM
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Default RE: Heeellllppppp.....

G'day Mate,
Check out all of the above, & also check for metal to metal contact anywhere on the plane, it is definately a vibration issue, as it only happens when the motor is running.
Also RX aerials have been know to get damaged in crashes, it would be wise to check your aerial & it's position relative to servos, aerial too close to a servo in the tail of a plane can cause havoc in the RX & hence the servos.
Old 02-07-2007, 02:32 PM
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Default RE: Heeellllppppp.....

Try a different set of crystals as well as all the previous suggestions. Don't even think of flying until this is resolved. Junk the receiver, switch, servos & nicads if you cannot find the problem. Cheaper than an accident.
Old 02-07-2007, 06:53 PM
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Default RE: Heeellllppppp.....

Of course my comment about changing crystals is the standard advice applicable in Britain and elsewhere where interchangeable crystals are normal. I think that US radio gear is probably made without this facility, so obviously you may need to change the whole receiver.

It is also worth making sure that the receiver is well protected by good quality foam etc in case of further crashes.
Old 02-17-2007, 09:52 PM
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matt12276
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Default RE: Heeellllppppp.....

Thanks everyone for all of the possible causes, I was just at a loss as to why it would only happen when the engine would fire up. I ended up going out and buying a Spektum DX 7 (just a little sooner than planned) and replaced the aileron servos. I still don't know what is bad, the servos or the receiver, but the process of elimination could be very expensive. I took the receiver apart and can see no physical damage to the board, but I did not get out the magnifying glass as someone mentioned. So maybe i will throw it in a beater plane down the road and see if she works!!

Once again I just wanted to say thank you for all of the good info, I appreciate it very much!!

-Matt

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