AR7100 and 8717 servos

[burke.bill]

Hey guys here's one for one of you guys to figure out. I just finished my Trex-600N build and am using JR 8717 servos on cyclic and also throttle so I can run everything but the Gyro on 8 volts. I am using the JR 8900G on tail with the solid G Gyro.

I am using the new Spectrum AR7100 and following Finless video I hooked everything up including throttle on the 8 volt side of my 7.4 lipo battery. and my Gyro and JR 8900g on the 5.2 regulated side.

Now I am very careful and took great pains to get all connections hooked up right. Sensors wire color the way they are supposed to be. Rudder wires to the right places. Throttle to the right place on the Multi-Gov Pro.

First thing that happened was the JR 8900g burned up it went all the way forward clock wise and seized up! No longer works. I was very carful to connect everything properly and it worked fine for a while as it should. I moved on to the Cyclic setup when it burned up.

I unplugged the 8900g and finished setting up the head, Then the elevator JR8717 servo did the same thing. What the hell is up with this. Is there a problem with this AR7100 or are the JR 8717s not going to work on 8 volts

But the real kicker is the JR 8900g was on 5.2 volts, yes the gain was on the 5.2 side as well.

Hate to even work anymore on this thing I feel like I just threw $218 away as I'm sure JR wont cover the servos. So now it will cost me $218 just to get everything up and running I sure don't want to burn up the rest of the servos.

Now I'm worried about did I damage the other servos as well? Are they about to fail? Any help or advise would be helpful.

Bill Burke

[jeffk]

I was planning on going with the 7100 and the 8717 / 8900G on my new 600, but after reading the release from JR stating that they were not recommending or supporting running those servos at 8v, I changed my mind and decided to run them through the Align 2-in-1 and an AR7000 at 6v. For the 8900G, I made up a voltage drop-down with two 1N4001 diodes in series which drops the voltage down to 5.0 volts just to be on the safe side. I'm not a good enough pilot to even notice the speed difference.

You mentioned that you hoked up your 8900 to the 5.2 volt port on the 7100. I would think this would have been fine, but you still burned up the servo. Odd. Have you put a voltmeter on that output to see if it's actually putting out the regulated voltage? Perhaps the receiver isn't working properly and is sending too high a voltage to the servo. Still, others have run these servos at 8v and haven't had any problems.

[helicraze]

I would check the output voltage. As for the servos on 8V it won't be warrantied.

[jhat]

I cannot speak to the 7100 but I am using the 7000 receiver and am running 8717 servos at 8V without any problems. I am using the Spektrum regulators to step down the voltage for the gyro, tail servo, governor and throttle servo as the throttle servo cannot handle 8v.

I have been flying this way all summer and no problems, so like many others the 8717 have not been a problem at 8v.

[Roadrune]

Have you bound the receiver? If it goes to one side, and keep going it will burn it no matter what the voltage are....
I suppose it will do that if you have not bound it...

[Pinecone]

Something was wrong to cause the tail servo to go up. Especially if it went hard over. And that alone could cause the burn out. If a defective Rx, JR should warranty the Rx and the tail servo. Also could be a bad gyro.

As for the elevator servo, it could be a defective servo. It happens. It may have burn out on 6 volts, or even 5. I do have assume that all linkages are free and not binding? And you didn't power up with the blade holder on?

But overall, this is why I went with a Scott Gray ReactorX on my Vibe 50. 6.8 volts to the cyclic servos and 5.2 volts to everything else.

Personally I would not run 8717s on an Align 2 in 1. It is only rated for 6 amps, and 8717s can draw 2.2 amps EACH. Plus the throttle, gyro, tail servo, etc.