If you need a Function Generator, this DIY Function Generator project is a simple way to get one built. If you would rather build a kit version take a look here. It uses a LM324N quad OpAmp at the heart of the project.
“The box I put the generator in is an old radio transcever box that already had the BNC Bulkhead attached, this was good for me as I don’t have any BNC parts laying around. I took the old BNC male RF pigtail, cut the end of, and soldered on some shielded wire and some leads.”