DS285 Servo Dead?

[ag4ever]

I have a DS285 servo I think is dead.

I had a minor crash where the blade struck my training gear on my Trex 450.

It bent the main shaft and shattered the one carbon fibe rrod for my training gear. Other than that there wa sno other damage. I repaired the bird, then flew it again. It flew great.

I went to put a second battery in, pluged it in and after the gyro initialized picked it up and placed it in the middle of my backyard.

Then I throttled up, and noticed the wanted to take off to the left. Like I was giving it left aileron. I thought it was just caught on some grass, so I moved it, but it was doing it again. This time I noticed the cyclic was at max negative throw on the left side.

So I pull the servo and notice a stripped gear.

I order new metal gears, and replace them. After replacing them I pull a spare reciever and battery pack and plug it in to test the MG DS285. The servo won't move.

OK, so I tear it apart again, and pull all the gears and plug it in. Still nothing. I grab the input shaft of the pot and spin it, the motor spins up. But when I spin the pot hte other direction, the motor stops.

I think great it is not dead, but the centering is off.

So I play with the stick position, and discover the servo only spins in one direction and won't reverse regardless of the pot/transmitter position combo.

Is the servo dead? Or can it be fixed?

[Pinecone]

Did you center the pot before you put the gears in? You said it was locked hard over. If you put the gears in centered, then the pot is already over one direction.

[ag4ever]

With no gears on it, I can turn the pot by hand, and it won't stop and reverse direction.

I would assume if the transmitter stick was in the center, if I had the pot to one direction the servo motor would spin, and when I twist the pot to the center it the motor would slow down as I get near the center and eventually stop, then when I go past the center it should reverse direction and speed up as I get further from center. This is assuming a constant center stick input from the transmitter.

Is that correct?

Right now it will only spin one direction. It seems like everything past center is dead band, or more correctly, the entire pot is one direction, and center is near end with dead band past it.

[Pinecone]

Actually with a digital servo it will run at full speed once the pot is away from the commanded location.

It sounds like a wire from the pot is broken or burned out, or the amp board is bad. I would pull the servo fully out of the case and check the pot wires to start.

[ag4ever]

Pinecone,

Once again, you are a wealth of knowledge.

I have discovered that the DS285 servos is not easy to disassemble completly. To remove the pot, it must be desoldered fom the board. There is a thin layer of plastic molded with the servo case that the pot sits on. Teh motor has some rubber type glue holding it in. That would not be hard to overcome, but since I did not know how the pot was held in, and it would not budge when I tried to push it out, I took my wire cutters and went to town on the case. I figured it was a dead servo and just chalked it up to learning how the DS285 is assembled.

So now ya know. To get it apart, just desolder the three pins furthest away from the motor. Then you should be able to lift the pot out and drop the board out the bottom.

Off to the LHS to get a new DS285MG I go.