cs70eb saw with motor problem

[eestibob]

Hi, I have a customer with this cs70eb saw at a window factory, I have replaced the brushes in the motor, checked the bearings wich seem ok but I still have a problem with the motor speed and power being unstable. set on full power  it will run full speed for a 15 to 20 seconds then start to slow then speed up a little then slow. the armature is a bit worn where the brushes contact and that is the only thing i see as a problem. how can I check the speed control and power supply pcb.
Any help would be appreciated.

Cheers from Estonia

 

[AlexThePalex]

Mine does that too. For all the years I have had it now, which is 8 or 9. And I don't think it is a problem, but by design. The saw has an electronic circuit that keeps the saw at a constant RPM, and to achieve this the saw changes the power output to keep the RPM constant.