I have found 4 out of 6 replacement tubes from my other Philcos radios and replaced them one by one and let it warm up. each time the sound degraded over time as before. The only tubes i didn’t have was the 7C7 and the 50B5. I have a 50A5 and a 50C5 and both have a different pin arrangement and can’t be substituted The 7C6,7B7 ,7A8, 35Z5 all check out as o.k. It’s looking more and more like resistors although there aren’t that many. My printer stopped working so I can’t download schematic diagrams. Until I get that issue resolved, I will put this radio on the side for now.
Gary K.