Relay chatter EF Johnson 500 ham radio transmitter What is the cause? How to locate fix the problem

First Johnson 500 in the shop for repair. The owner brought it to me with the complaint, no power up and has a hissing/buzzing sound from the power supply. I thought, hopefully it is not the main power transformer! Well, lucky it turned out to be a defective relay (RY301) Due to age, it lost inductance, the relay could not pull in and started chattering. Found a suitable replacement in my stash, replaced after making and adapter plate. Now it is working great! Super happy that there was not other issues. These units are very difficult & heavy to work on. When they are operational, you have the Cadillac of ham AM transmitters! Love the old gear! Hope you like. TD