Servos Servo Mystery

Eggy 71

Member
I had a hard landing to put it mildly and did a little damage to my Trex 450. New main blades, main shaft, tail boom and torque tube. Aileron and pitch servos needed some fixing too. I've come across an issue with one of the servos. Pitch servo stopped working after the crash. I pulled it apart found no gear damage, lubed and put it back together. All seemed to operate fine. While fine tuning setup again in sub trim servo has stopped working. Connections seem fine, the only thing I can think of is an internal connection gone bad. Does anyone have any other thoughts?
 

Tony

Staff member
Either the servo was put into a bind and over heated and burnt the motor causing it to work on and off, or maybe a crack in the circuit board. Could also be a dirty pot. When it stops, try moving the servo arm and see if it will start working. If just moving the servo arm makes it start working again, then you know it is either a dirty pot, or a bad motor. In most cases anyway.
 

Eggy 71

Member
It's completely inactive. The channel from the microbeast is still operational. I switched servos for that check. It's a head scratcher as it just decided to stop working while adjusting subtrim. Better than it stopping halfway through its first flight back I guess. I'll have to order a whole new servo. Time to start my next project, while ordering replacement parts for the the 450 I added this to the cart. I have been looking at it for 3 months but couldn't pull the trigger on getting it until now.
 

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Tony

Staff member
I would play it safe and order all 3 servos. That way you know they are matched and you will not have any issues. Keep the other two as spares in case of a failure. But definitely don't run the one that keeps quitting on you.

And sweet deal about the 700. I can only hope to get one of those one day. Keep us updated on the progress of that monster.
 

Eggy 71

Member
Here's an interesting development. I put the 450 aside because of the bad servo and started assembling the 700x. It's going together nicely, I'm lovin it, it is massive. I used the 450 electronics to center the 700x servos to attach the servo arms in the right position. Would you believe one of the ds825m servos was dead and plugged into the same channel as the bad 450 servo? That made me rethink the whole problem, was it a bad beastx gyro. To make a long story shorter, gyro seems fine, any other servo works on that channel and the bad 450 servo and 700 servo don't work in any channel. What would you say the chances of that were? It had me scratching my head for over an hour yesterday.
 

Tony

Staff member
It almost sounds like the gyro is pushing out full voltage on that one port. If it were me, I would take that as a sign that the gyro is toast. My first step would be contact Horizon to see about getting a replacement. You will have to send yours in and I do hope they test it. And hopefully they send you a new one, or at least a returned item that is in good working order. Nothing worse than losing a servo for no other reason than just plugging it in.
 

Smoggie

Well-Known Member
The DS825M is a tail servo, only one of those is supplied, the other 3 are the swash servos and should be DS820M.

If you have it connected to the rudder servo port on the FBL then maybe you have the centre pulse set wrong? It should be 1520us

If other servos work normally on all ports there is no reason to suspect a FBL fault. Bad servos do happen, I had a faulty DS825M on my 700X too, it failed first time out and caused a crash. The dealer should replace it for you.
 

Eggy 71

Member
I'm going to confess even though it's going to make me look stupid. I was plugging that one servo upside down. All the conductors are inside the outer jacket and the orientation is pressed on the connector surface. I don't know how I mixed that one servo up but the negative port was connected to the signal wire and vice versa. I took both servos to the LHS before I ordered anything . The 450 servo was toast but the 820M worked fine.

One one other note , on the 700x I notice the pitch and aileron servo just clear the reinforcing bracket and just make contact with the carbon fibre frame at the top of the stoke. Smoggie, Do I remember you having a similar problem. Did you need to shim the servos?
 

Tony

Staff member
No worries, I just did this on a Goblin 570. Couldn't figure out why in the world the ESC would not initialize... Then I looked at the Ikon and saw the brown wire up top lol. It happens to the best of us. Trust me, this will not be the last time you do that lol.
 
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