So....I posted a thread a little while back about flickering dial lamps on this particular 4000. I recapped the ripple filter board and protection board, but left the rest of the caps be. They are original to the unit and are 47 years old and seem to be working fine. In retrospect, the caps I replaced probably were fine as well, but I figured best to do it since it was in the power supply circuits. Anyway, after cleaning the selector switch with Deoxit a few times and thinking that my problem may have been power load related, as it had not gone away after those attempts, I realized I may be overlooking the obvious. Turns out the issue was the bulbs themselves! Changed out all five and the dial lights up fine like its supposed to and no flickering. Moral of the story: never assume that just because the original 47 year old lamps are working and appear good, that they are!