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Old Jun 16, 2011, 06:10 PM
Registered User
Joined Jun 2011
22 Posts
Question
4 channel MJX F27 servo problems?

I have purchased a MJX F27 about a month ago from an ebay seller
when it arrived the battery was no good the heli would only fly about a foot off the floor, the seller sent me out a replacement battery but it was a 701855xL / S032G a syma replacement witch did not fit the holder so I use an elastic band to hold it under the skid and it works,ok

over all it seems pretty durable for a cheap heli however I don't know if it has a problem or not?

it has two servos but only one seems to move

I have the remote in mode 1 throttle on left & direction on the right

when I push the right stick forward the right servo goes up, when I pull the right stick back the right servo goes down thus moving the swash plate as it should.

the problem is the left servo never moves, to my understanding when I move the left throttle stick forward and leftward or rightward the left servo should move the left side of the swash plate causing forward roll movement, or does this servo only move when you adjust the trimmers ?

other than that it seem to function good I am not very impressed with transmitter (no memory for adjusted settings) once you turn power off and the digital trimmers are a bad idea (trying to watch the flight and remember witch trimmer is for what when you are new to this model then remember the numbers for the settings all at the same time is confusing ) analog sliders or trimmers would have been a better idea.

the F27 heli flies nice but heavy and the motors seem to run slower & hotter than my 33cm IR R102 in door heli

the only complaint I have about mjx heli's is most are under powered
using a 3.7v 500mah lipo
the battery has to be in perfect condition because it needs the 4.2v full charge to get it off the ground , when voltage drops below 3.9 you can not do any maneuvers due to loss of power to the rotors when the servos are engaged, and when the heli can no longer fly you are at 3.8v
so for a 4 ch heli its not very good you get 2 to 3 minutes of flying & another 2 to 3 minutes of hovering if you are lucky. where the MJX T23 & T34 both have a 4.7v battery more suited for the extra power requirements of servo controlled heli's, but for the price its ideal radio heli for beginners or a spare for your friends to fly.

Joe
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Old Jun 17, 2011, 10:13 AM
Registered User
scorp's Avatar
Cupertino, CA
Joined Nov 2010
2,381 Posts
Quote:
Originally Posted by JoeNezZ View Post
the only complaint I have about mjx heli's is most are under powered
using a 3.7v 500mah lipo
the battery has to be in perfect condition because it needs the 4.2v full charge to get it off the ground , when voltage drops below 3.9 you can not do any maneuvers due to loss of power to the rotors when the servos are engaged, and when the heli can no longer fly you are at 3.8v
so for a 4 ch heli its not very good you get 2 to 3 minutes of flying & another 2 to 3 minutes of hovering if you are lucky. where the MJX T23 & T34 both have a 4.7v battery more suited for the extra power requirements of servo controlled heli's, but for the price its ideal radio heli for beginners or a spare for your friends to fly.
i'll let others who have this bird comment/resolve your issue but the voltage metrics you provided relative to performance is very good info.
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Old Jun 18, 2011, 12:06 PM
NotAnotherMomentLostToSei zures
Chap1012's Avatar
United States, MA, Malden
Joined Mar 2008
11,322 Posts
First that is a mode 2 heli: http://www.rcuniverse.com/forum/m_4978142/tm.htm
Throttle and rudder on left stick. Elevator and aileron on right stick
And it sounds like the correct battery size: http://www.rc711.com/shop/mjx-f27-mi...or-p-4161.html

Servos really don't use that much juice. It sounds more like a mechanical problem. If you crashed it, start checking the shafts for straightness (spinning true). Check the gears for missing teeth and tight binding. It is usually a binding problem (shafts/gears) that will run a battery down fast. This is true for any coax. If everything checks out ok, it could be another bum battery. I know....that sucks!

Mike.

EDIT: Make sure all your trims are centered EXCEPT the throttle trim. The throttle trim should be all the way down. This "could" be the problem. Lets hope it is that easy.
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Last edited by Chap1012; Jun 18, 2011 at 12:12 PM. Reason: trim settings
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Old Jun 19, 2011, 11:22 PM
Different fly 4 different guy
gordonzo's Avatar
Canada, BC, Salmon Arm
Joined Jan 2011
1,892 Posts
Quote:
Originally Posted by JoeNezZ View Post
I have purchased a MJX F27 about a month ago from an ebay seller
when it arrived the battery was no good the heli would only fly about a foot off the floor, the seller sent me out a replacement battery but it was a 701855xL / S032G a syma replacement witch did not fit the holder so I use an elastic band to hold it under the skid and it works,ok

over all it seems pretty durable for a cheap heli however I don't know if it has a problem or not?]

it has two servos but only one seems to move

I have the remote in mode 1 throttle on left & direction on the right

when I push the right stick forward the right servo goes up, when I pull the right stick back the right servo goes down thus moving the swash plate as it should.

the problem is the left servo never moves, to my understanding when I move the left throttle stick forward and leftward or rightward the left servo should move the left side of the swash plate causing forward roll movement, or does this servo only move when you adjust the trimmers ?

other than that it seem to function good I am not very impressed with transmitter (no memory for adjusted settings) once you turn power off and the digital trimmers are a bad idea (trying to watch the flight and remember witch trimmer is for what when you are new to this model then remember the numbers for the settings all at the same time is confusing ) analog sliders or trimmers would have been a better idea.

the F27 heli flies nice but heavy and the motors seem to run slower & hotter than my 33cm IR R102 in door heli

the only complaint I have about mjx heli's is most are under powered
using a 3.7v 500mah lipo
the battery has to be in perfect condition because it needs the 4.2v full charge to get it off the ground , when voltage drops below 3.9 you can not do any maneuvers due to loss of power to the rotors when the servos are engaged, and when the heli can no longer fly you are at 3.8v
so for a 4 ch heli its not very good you get 2 to 3 minutes of flying & another 2 to 3 minutes of hovering if you are lucky. where the MJX T23 & T34 both have a 4.7v battery more suited for the extra power requirements of servo controlled heli's, but for the price its ideal radio heli for beginners or a spare for your friends to fly.

Joe
Joe -which other MJX helis do you have? We have several F27's in our family and have had very few problems.

On factory default settings the aileron servo does not move much. Increasing the tx settings will increase the servo range (and movement).

In mode '1', when you push the left stick to the left or right, if your heli does not 'side-fly' in that direction you have:
(1) bad servo (mechanical problem)
(2) bad board (electrical problem)
(3) tx servo aileron rates are set too low

Incidently, on the show Red Green they say that if you can't fix it with a hammer and duct tape, you got an electrical problem.

The tx factory settings are only good for hovering around indoors. I would suggest you max out the fwd elevator servos and really crank up the throttle curve (0-60-75-90-100) to compensate for the weight. We have some with 50+ flights and still have no trouble getting 5 min flight time but we also have to do the 'crazy' stuff on the first half of the battery or it's easy to drop them. All of our F27's do retain their settings. And 5 min (+/-) is normal fly time for most helis.

I also fly the small T38 3ch for indoor fun, and a larger F28 4ch for indoor or outdoor. I also have the 3ch T-34 and the behemoth T23 which is a 3ch but with adjustable servos instead of a tail motor. The T34 and T23 both have 7.4V batteries but still fly 5 minutes or so. Battery voltage is not related to servos or no servos.

Quote:
Originally Posted by Chap1012 View Post
First that is a mode 2 heli: . . .
The F27 comes from the factory in mode 4, which they call mode 1. A few clicks can also change it to mode 2 (the real mode 2).
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