There's nothing wrong with using a cheap function generator for checkout. Sine wave distortion will likely be 1% or more. If you have a scope play with the square wave genrator and watch what happens at the frequency extremes.
I appreciate the suggestion on trying new things on the generator. I am a flat out novice. Love messing with this stuff since a little kid. I learn as I go and pick up equipment the same way. If I feel I need it I am getting it some how because I love working on the vintage. Oh, don't worry I don't do any work for the public lol.