Scale Soaring UK

I found an intermittent operation problem with one of the Hobbyking 300mm servoless spoiler units the other day - appeared to operate ok until leads touched near point where they entered the unit, then after a bit of lead manipulation it sprang back to life, then later stopped again.
As there is no way that it is worth trying to return the unit to HK, I decided to try to investigate the cause of the problem.

The problem appeared to be with the wiring just inside the motor unit as the fault could be fairly well repeated at will & cured by gently pushing/pulling the servo/feedback pot wires where they entered the motor unit. Thus I reckoned I needed to get inside the motor unit - but how?

The motor unit is fixed to the spoiler framework by 4 screws, so those were removed but the motor unit couldn't be detatched from the frame.
The motor operates the spoiler blades via a screwjack with a feedback pot pin engaging into the screwjack axle. I carefully removed the feedback pot by very carefully breaking the epoxy type glue blobs at each end of the pot & then levering the feedback pot unit off of its two small black double sided sticky pads (one at each end).
There is a small black plastic clip at each end of the top of the spoiler channel. If the motor end one is carefully removed (lever up motor side of clip as it has two pegs which rest under the flat tops of the frame), this allows the frame to open slightly, releasing the trapped motor unit.
The 4 motor unit casing screws can now be removed and the casing spits down the centreline. Lift off the screwhead side half to leave the motor etc. in the lower half.

You can now see what is in the photo below.
The motor & servo cable wires connect to the very small PCB via the rubber grommet (which could easily be slid back away from the unit).
The 3 servo lead wires connect to pads on the front Right of the PCB, whilst the 3 feedback pot wires connect to the front Left.
The problem was that the insulation on all 3 feedback pot wires had shrunk back (caused by too much heat whilst soldering), allowing one or more of the bared wires to short to the servo lead connection pads as the wires flexed outside the unit.
(I would guess that the feedback connections are made off as the last operation during overall unit assembly).

I disconnected each of the feedback wires in turn, minimised the bared wire length & resoldered the wire. (Note that this needs magnification aids and a very small tipped iron)
Result: A fully working & non-intermittent spoiler unit after reassembly.
I initially checked operation with the feedback pot pin engaged with the screwjack, but held in position. Once confirmed ok, I then re-secured the feedback pot unit to the frame with a couple of blobs of epoxy.

All this may be useful to others who have HK servoless spoiler issues and want to try to repair.

Well done Peter, Thanks for sharing, Terry.

Thanks Terry.
I should have mentioned that the implementation of other available servoless spoilers is probably very similar to that of the HK marketed types, thus the mechanical arrangement shown in the photo is also likely to be representative of those.