ZTW 12A ESC Repair – Brain Surgery

I’m not exactly sure how this happened, it wasn’t a propeller, but one of the ZTW 12A ESCs was nicked by something as it struck a tree.

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Comparing it to another ESC (which has some blown FETs on it), this managed to dislodge no less than 7 small SMD parts off the PCB, 3 ceramic bypass caps, and 4 resistors.

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The parts that were knocked off the board are high-lighted in yellow on what becomes a donor board:
(I didn’t have any other new ZTW ESCs to swap out with!)

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As all these parts are “passive” components, it won’t be a problem to rat them off the faulty donor board:

Luckily none of the PCB pads weren’t damaged.

Pads were cleaned up with solder wick, and given a gentle brush (using a second-hand soft toothbrush) with PCB cleaner.

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Working with these tiny 0603 SMD parts can be challenging, but a small tip in the Weller iron, 0.5mm solder, some tweezers, and a maggy lamp can make it a relatively straightforward job.

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I’m glad I kept two of these stuffed ZTW ESCs… because during the brain surgery, two of the parts flicked out of the tweezers, never to be seen again. 🙁

This is with all the replacement parts fitted:

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One of ceramic capacitors isn’t exactly dead level on the PCB, but the solder joints are good, and this isn’t a beauty contest.

Make sure there are no solder shorts between the parts due to their close proximty – use a maggy lamp to check.

Up until this point, the repair was done in situ, and the motor wires were not removed.

At this point I could have wrapped the ESC in black (of course 😉 ) electrical tape and then taped it back to the arm, but I decided to finish it off properly, and cover the ESC with 20mm black heatshrink.

Of course, this meant unscrewing the motor, de-soldering the motor wires, sliding the heatshrink on, re-soldering motor wires and shrinking the heatshrink.

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Once all reassembled, a short hover test was performed in the yard, and the patient was diagnosed all OK, and discharged!

🙂

If you find yourself in this situation, give it a go!
Tasks like this are good for honing your SMD re-work skills.

All it cost was about 40 minutes of time, and saved throwing away an otherwise perfectly fine ESC.