1939 model 39-30 - Printable Version
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Home Radios (https://philcoradio.com/phorum/forumdisplay.php?fid=6)
+--- Thread: 1939 model 39-30 (/showthread.php?tid=7469)
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Home Radios (https://philcoradio.com/phorum/forumdisplay.php?fid=6)
+--- Thread: 1939 model 39-30 (/showthread.php?tid=7469)
Pages:
1
2
1939 model 39-30 - NostalgiaRadioTime - 09-14-2013
Just finished restoring this. It took three #75 tubes until I found a good one that didn't cause a muffled hissing after the set played for about 5 or 10 minutes. As soon as you'd just touch the top of the cap on the tube, the hissing would cease. It looks a lot more shiny than it really is. The flash made it look too glossy. I had just applied a coat of Liquid Gold spray to the cabinet, and the excess that didn't wipe off hadn't dried yet.
RE: 1939 model 39-30 - Radioroslyn - 09-14-2013
Nice Job! Look lke an eastern set, most of those stations I can get over here. WCAU is WPHT now as of 10 or so years ago. I don't understand why stations change call signs after many many years. Kinda like us hams the FCC has allowed us the to have call signs which don't necessarily have to be in the call district we are in. It's a bit of annoyance you think the guy is in Calf. but he's next door.
Terry
RE: 1939 model 39-30 - Bill Kinghorn - 09-14-2013
Any stray capacitance between the 75 grid cap and the plate of the output tube ( 41, 42, etc.) can cause hi freq audio oscillation. Dress the grid lead away and/or try some shielding.
RE: 1939 model 39-30 - Jamie - 09-14-2013
Beautiful radio. Great job!
RE: 1939 model 39-30 - Tom Hamilton - 09-20-2013
I've got a 39-30 as well. I have seen some 39-30's with only 1 tube shield, on the 75 tube. For whatever reason, my radio has provisions for two tube shields, on the 75 and the 37. But, when I got it, it only came with only 1 actual tube shield installed, on the 75. Could that be part of your problem?
Tom
RE: 1939 model 39-30 - TA Forbes - 09-20-2013
Bill/Tom: great advice. Funny thing about 75 tubes, the mutual conductance of the triode is only 750 uMhos, and it doesn't take long for it to degrade to the 500 range. In sets where the 75 is the only AF amp before the output tube this can be an issue.
Also: 42 tubes can be noisy after they warm up. Same goes for 6F6 tubes.
RE: 1939 model 39-30 - TA Forbes - 09-20-2013
OH YES, very nice job on you set!!
RE: 1939 model 39-30 - NostalgiaRadioTime - 09-20-2013
Mine only has one tube shield too over the 75 tube.
RE: 1939 model 39-30 - wa2ise - 09-20-2013
Quote:It took three #75 tubes until I found a good one that didn't cause a muffled hissing after the set played for about 5 or 10 minutes
That might have been a supersonic parasitic oscillation. A "grid stopper" resistor, around 68K, placed in series with the grid wire right at the top cap of this tube (its grid), should tame those unruly tubes you have. This resistor, in combination with the tube's stray capacitance, acts like a low pass filter to disable the oscillation.
RE: 1939 model 39-30 - wireless - 09-21-2013
Real nice looking set--great restoration !
RE: 1939 model 39-30 - NostalgiaRadioTime - 09-21-2013
Thanks, everyone. The set is working fine now. I think it had a lot to do with shielding around that 75 tube. No more muffled hissing.
RE: 1939 model 39-30 - NostalgiaRadioTime - 09-21-2013
I really like the rear lighted dial on these 1939's. And, using the "Rebuilding Philco Pilot Lamps" tip found in the tech section ( http://philcoradio.com/tech/lamps.htm ) it no longer flickers on and off!
RE: 1939 model 39-30 - Electrothaumaturgist - 09-21-2013
Still love those wine flavored buttons!
RE: 1939 model 39-30 - Arran - 09-21-2013
Another thing to watch for on a 75 tube, or any other glass tube with a grid cap, is the solder joint on the grid cap giving out. Also the clip on the end of the grid lead can have problems, the solder joint going bad or the wire breaking internally.
Regards
Arran
RE: 1939 model 39-30 - Eric Adams - 09-22-2013
Wow. Really great restoration!