[KCMike]

Hi Mike. Do you have a frequency counter? If so you can hook the signal generator to it and check for accuracy of the generator. You probably should replace the electrolytic caps in it.
Other members on here can give you more detailed advice on what you should do.
Here is a video on one very similar to yours that could help you with how they work.

https://www.youtube.com/watch?v=eE7J4Kpbe6w