My trusty Bosch CSB-420E hammer drill came back after a hard session with my son-in-law with a fault. There were two things, the speed controller on the trigger did not work, it seemed to be stuck and there was an intermittent electrical fault, ie it would only fire up in certain positions.
The drill is easy to dismantle with a couple of phillips screwdrivers to remove the screws holding the two halves of the case together.
I suspected that there may be a broken wire where the cable enters the drill. The reinforcing grommet had long since snapped where the cable enters the handle.
I undid the cable clamp and two terminal screws noting which colour wire went into which terminal. I measured how much cable to cut off and removed sufficient out cable shield and bared the connection cable. The originals had brass ferrules but I had to just twist cable and insert into terminal connectors and screw down tight.
I checked the brushes etc whilst I had the chance, all seemed ok.
The speed controller I managed to loosen up with a pair of pliers, I think it was just jammed with grit or dust.
I reassembled the drill and bingo it worked perfectly, including the speed controller. Hopefully lasting another 30 years or more!
