A coworker is having issues with a 3-terminal voltage regulator. I don't know which part, but for the sake of discussion let's use one like the LM317T. Anyway, in circuit its output looks like a sawtooth wave instead of being well regulated at around 1.5 volts. Is there a likely simple explanation, or somewhere I can direct him to investigate (such as input bypass cap failure)? Or do I need to get more details from him (amplitude, DC bias, frequency range) before anyone can take a quick crack at this?