Thread: Bosch sliding mitre compound saw - intermittent running

Dear Mhunter,

The problem certainly sounds "switchish" alright. Sometimes just a retightening of the little screws that hold the wires in the switch-assembly is all that is needed in such a case. But going by my brother's experience with that same model of saw, it might also pay you to have a closer look at the Commutator, to see whether any of the individual slip-ring segments have delaminated from the Armature. Symptoms are a little different in such a case - in so much as total-shutdown doesn't occur, but intermittent speed and power does. Brush-wear would be much higher than normal, and there would be telltale signs of caked black deposit at one spot on the inside of the transparent blade-guard. But your situation certainly sounds more switchish at this stage.

Best Wishes,
Batpig.

Is there a cable that is flexing as the saw is lowered?

There is a chance that the copper inside has fatigued & broken & it is only the insulation that is holding the ends together until it is moved.

Ahh yes! I will see if it is the cord, switch (or hopefully not other) and let you know.

Originally Posted by Batpig

Dear Mhunter,

The problem certainly sounds "switchish" alright. Sometimes just a retightening of the little screws that hold the wires in the switch-assembly is all that is needed in such a case. But going by my brother's experience with that same model of saw, it might also pay you to have a closer look at the Commutator, to see whether any of the individual slip-ring segments have delaminated from the Armature. Symptoms are a little different in such a case - in so much as total-shutdown doesn't occur, but intermittent speed and power does. Brush-wear would be much higher than normal, and there would be telltale signs of caked black deposit at one spot on the inside of the transparent blade-guard. But your situation certainly sounds more switchish at this stage.

Best Wishes,
Batpig.

We have a winner!!!
Looked at cable continuity from 3 pins into the machine - all good.
Checked connections into terminal blocks - one was a bit loose and came out with a small tug.

I thought that might have fixed it, but no.

I went in again, continuity test on the switch, yep it seemed suspect. Took the switch out, and pulled it apart. One of the copper switching plates was making a poor connection on activation, had some small "burns" and the copper was pitted. A little bit of wet and dry, then moving round a bit of the internal grease and its all good. I know its a temporary fix, but at least I know that the switch is on its way out.

Thank you both for your help.
PS the cleaning of the brushes and commutator seems to make it go harder so it wasn't a waste - well thats what it seems like anyway.
Cheers Woodys!!!