How to test Dow Key relay Ex. EF Johnson 500 High power Ham Radio tube transmitter simple procedure

Have seen this issue many times in the past. Transmitter outputs power, dow key fails to toggle, boom! damage to the transmitter. Not a good situation, however there is a easy fix, test the system before putting it into operation. Yes, this may be common sense, but we all get in a rush, forget to look at the small things, then they turn into big issues. Here are a few simple steps to check the system and avoid damage.