?

My wife's Frister & Rossmann foot pedal is not powering the sewing machine when it is depressed. The light does come on so power is okay. I have opened the unit and cannot find any thing wrong.
The machine is around forty five years old, model no 16803889 if this is relevant.
I would be greatful for any suggestions, it has sentimental value since I gave it has a 21st birthday present. I know times have changed!

With thanks......