[dconant]

Hello, This Philco 89 code 123 is playing now. Problem is it plays for a long time then the signal drops off quite a bit. Played all day Saturday in the cabinet unbolted. So I decided must be good to go so bolted it down. It played perfectly for about 15 minutes and signal dropped off. If I touch the top of the 77 tube signal comes back some but not all the way. So I thought maybe antenna coil. So pulled it out looked at the coil and all sections ohm out close to what schematic says. Checked for green corrosion finding none.  While I was in there I checked for loose connections and found none. Fired it up again yesterday and it ran about 4 hours and again dropped off. Pulled it this morning checked again for loose connection and also soldered all rivited grounds and replaced the 300 ohm wire resistor to pin 4 with 2 watt 270 ohm metal oxide resistor. Fired it playing for about 5 hours with same problem repeating. I quickly measured B+ at one of the compensators sticking out the back. That bought the radio back to normal signal. I have changed the 77, 75 and both 44 tubes twice. The connections to that compensator are good. I have even covered the radio partially with a towel to see if it is heat related but I doubt it. Changing tubes will the signal is low makes no difference. Let cool down several hours it comes back normal. Other than that it plays quite nicely.

Anyone have any ideas? 

Thanks,
Dan