Probably the first thing to fail, assuming normal use is the POWER CORD.
I have seen many failures in POWER CORDS where the STRAIN RELIEF is located.
The wires inside the strain relief are broken due to the stresses applied to them by constant movement focused on the relief it's self. I am not sure this is very clear - but, lets assume that the appliance is intermittant, it's reasonable to assume the simpliest first - is it the power cord?
Before replacing the Brushes, with very fine emory, be sure to clean the (is it the commutator?, I forget) surfaces where the brushes contact.
Hope this helps.
cfm |