I have an electric lawnmower from Black n Decker. I had it for about 7 years now. It stopped working all of a sudden.
I replaced the bridge rectifier and cleaned the brushes.
Runs like new now!

Some important info before buying:
It appears that the original bridge rectifiers (Black & Decker P/N 72256-03)are rated at 400 volts and 15 amps.
Suitable replacements include almost any bridge rectifier with the same or HIGHER ratings. For example: P/N BBPC2504 or MB254 are rated at 400 volts and 25 amps.

Here are some links online for the parts that you might need:
Black and Decker bridge rectifier:

suiable replacements:

Here is a link for the switch in case that is what you need:

Or those shunt brushes that I showed at the end of the video (the ones that I cleaned):