Maintaining The Collins R-390 Receiver

A bit of regular maintenance on the Collins Radio R-390 receiver. I had an issue a couple of weeks back where I was noticing a decrease in sensitivity and found a weak IF tube. After replacing the weak tube, I ordered more spares (I probably have 20+ spares of 6BJ6) but wanted to share my philosophy on maintaining and keeping in tip-top shape the vintage boat-anchor radio equipment from the 1950's and 1960's.