Thursday, 7 February 2013

HobbyKing HK-310 throttle return mechanism repair

Can you spot the problem with the throttle trigger in the following picture?

If you look carefully, you can see that the throttle trigger on the right transmitter is slightly depressed towards the grip. This is due to a fault in the mechanism that returns the throttle trigger to the centre when you release it.

Fortunately it is not difficult to fix this issue.

WARNING: This and other DIY projects are purely "at your own risk". If you are at all uncomfortable or inexperienced working with electronics, please reconsider doing the job yourself.

This problem happened on both of our transmitters after a few months: suddenly the vehicle would run off by itself because the throttle does not return to neutral properly.

To fix this issue you need the following tools:

  • A size 1 Phillips head screwdriver
  • Needle-nose pliers to unhook and hook the spring of the return lever
  • A 1.5 mm drill bit
  • A 2 x 10 mm self-tapping screw (not shown in the photo)

The transmitter can be opened by removing seven screws on the back.

Note that the screw on the right top is of shorter size then the rest of the screws. This will be important when closing the case.

After the screws have been removed the case can be lifted easily, but you must separate the stickers in the battery compartment. You will be presented with the guts of the transmitter as shown in the following image:

To address the issue with the throttle you must remove the throttle assembly, which is held in place with three screws. You must also disconnect the plug from the throttle potentiometer to the main board.

With the throttle mechanism removed you can easily see the problem: the lever that returns the throttle to neutral is hinged on a tiny plastic pin, which breaks due constant stress caused by the strong spring.

The fix the issue break off the pin completely and drill a 1.5 mm hole into the stud. Be very careful as there is not a lot of flesh in the plastic.

Now use the 2 x 10 mm self tapping screw as pivot point for the lever. Ensure that the screw is loose enough to let the lever move freely, yet tight enough that it can not disengage.

The screw goes into a lot of plastic material so this repair will certainly out-last the life of other components in the transmitter.

Re-assemble everything and pat yourself on the shoulder for a job well done!