Background
My neighbour was in the garden one day and was having trouble with his strimmer. The motor was running intermittently and cutting out. As it was just over a year old i decided to have a look at it to see if it could be repaired. It was one of the higher end of the market models so i decided that a bit of time was worth spending to save it from a trip to the recycling yard.
Unfortunately i did not take many photographs of the work as i got a bit tied up dismantling the casing. I have never come across such a relatively simple piece of equipment with so many securing screws and interconnecting pieces of plastic. The unit was clearly not designed for maintenance or repair, simply build, use and discard. A real shame really as all the parts were of good quality plastic and mouldings.
Unfortunately i did not take many photographs of the work as i got a bit tied up dismantling the casing. I have never come across such a relatively simple piece of equipment with so many securing screws and interconnecting pieces of plastic. The unit was clearly not designed for maintenance or repair, simply build, use and discard. A real shame really as all the parts were of good quality plastic and mouldings.
The motor was removed from the plastic mouldings and carefully examined. As the problem was intermittent i did not want to displace any parts that could make the problem worse or make it disappear for a while. The motor was a standard series wound universal type motor with carbon brushes. I examined the brushes and commutator and found they were in good condition. While doing this i noticed that the connections to the stator winding copper wire were made with insulation displacement connector(IDC) type devices, basically a two prong blade where the wire is forced down detween the blades cutting('displacing') the insulation and making contact with the copper wire beneath. This is a common practice in electronics partiularly on ribbon cables. I could see that the wires had been pushed into the IDC at an acute angle rather than at 90 degrees to it. When i checked the continuity using a DVM it varied particularly when i touched the cable with a screw driver. After a few touches the copper wire broke away from the IDC.Clearly this was the problem. As the wire was now too short to reinsert into the IDC i cut the plastic cable ties securing the stator windings in place and unwound one turn from the stator. The length of copper wire can be seen in the photograph. I then correctly inserted the wire into the IDC and cut off the excess wire. I repeated the same process for the other connector on the second half of the stator as the original wire was also badly installed. I checked the continuity using a DVM and bench tested the motor successfully. Over the past couple of years the strimmer has been happily working away. It is just a shame that the wire was so badly installed in the first place.