For fun and a good learning experience, I just started evaluation and repair of an old hp 652A Test Oscillator (circa late 60s) and would like to share lessons learned with anyone who is doing the same or has an interest. First observations: Distorted sinusoid output, so I am looking at the oscillator PCB, first. The unit has old style Sprague axial electrolytic caps, which I will likely need to replace once I test their ESR and D. The unit has double sided through hole PCBs with excellent hp workmanship.