I have a Philco 40-180 that I had restored electronically. It plays well for awhile, but after a few minutes, volume decreases significantly (almost inaudible). When I turn up the volume it sounds fine. However, the volume will eventually go back to the original level (loud) and need to be turned down. It cycles back and forth. I think it could be related to the 84 tube. When volume decreases, I can tap/move the tube a little and the sound will go back to normal for a short time. I replaced the tube just to be sure, but see no change. Also, when volume decreases, I can turn the set off and immediately turn it back on and this seems to reset the volume to the correct level. But again, volume will continue to cycle. I am hoping someone on this forum has insight into this issue.
I'd start by cleaning the tube socket. Spray some contact cleaner or DeOxit in the socket and work the tube in and out a few times. Might not be a bad idea to do this to all the tube sockets. That you can do without removing the chassis. Let the radio sit for at least 15 minutes before trying it to allow the cleaner to evaporate. If that doesn't clear up the problem, you'll have to pull the chassis and try spraying some cleaner into the volume control itself under the chassis.
These things may or may not clear up the problem but try the easy stuff first!
+1 what Greg said. The Loctal sockets and tube pins are a PITA! I picked up some dental brushes at the local pharmacy. I gently work a brush into the socket, spray a little contact cleaner (And I emphasize, a little!) then work the brush in circular and up and down motions. I try to clear problems trying anything that doesn't cost me first! Take care and BE HEALTHY! Gary
Thank you for the suggestions! I will try these first and see if that resolves the problem.