Makita Hammer Drill Phase Repaired
I was given a cordless Makita hammer drill that had an intermittent fault. It would work sometimes and other times it would give very weak movement and would only start again if you tapped the side of the drill.
After pulling the side covers off, I tested the switch operation and worked toward the motor. This is a brushless design and to be honest, I hadn’t had much to do with these before. After some time researching on the internet, I was able to do further testing with confidence. Rather than having a typical stator and a rotor made up of an electromagnet, the brushless design has the electro magnet in the stator position. To gain the rotation and torque required, an electronic controller is responsible for the process of commutation using a 3 phases. This creates current that is staggered, timed precisely generally using Hall Effect sensors to gain the most torque possible.
Armed with this knowledge, I continued by repair. I noticed that when the drill would not rotate, it would still try and give the typical hum noise. After looking closer at the controller, I noticed a slight burn mark on one of the phases. After checking for the security of the wire, the terminal came completely out of the controller!
I carefully examined the terminal and was surprised at its design. Rather than being secured into the controller, it was merely pushed in with a barb design and then held in with the insulating resin. After removing a large amount of the resin to access the terminal base on the circuit board, I was able, with much difficulty, to solder the terminal back onto the board. After this a layer of Araldite to insulate the joint was used as I did not have the correct resin available. I checked the melting point and this appeared within range.
After further testing and use I was able to give the drill back to the customer with the confidence that a successful repair had been accomplished.
This article was prepared for you by Mark Rabone from Australia.
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