Philco 20 - next project - Printable Version
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RE: Philco 20 - next project - rfeenstra - 12-20-2020
thanks Russ. I've look at that high temp silicone but have not purchased any as yet. Gonna have to do it!
RE: Philco 20 - next project - rfeenstra - 12-20-2020
It plays again. The resistors ore the originals with a parallel resistor hidden underneath to bring each resistor back to specs (I took the picture at an angle that hides all of them!). The chassis is the original plating cleaned up with a very thin clear coating to protect it. Arran, I didn't realize that some rust removers may leave a protective conversion coating. I may just rely on that in the future! The tin plated tuning cap certainly looks different than the chassis but I really don't mind. Kind of matches the capacitor can. Next, I need to work on the speaker a bit to clean it up.
Question: Most voltages are reasonable given the higher line voltage (thinking of adding a bucking transformer) except on the 2nd detector. The chart says that the plate voltage should be 35 volts. I get closer to 110 volts. The grid is only about 2 volts negative compared to the cathode so the tube should not be close to cut off causing a high plate voltage. Screen is at about 10 volts rather than the 2 volts listed. This voltage comes directly from the voltage divider through a 250K resistor. Result is the same with different tubes. Any ideas?
The radio is tuned to 740, Zoomer Radio, Toronto in these photos. Sounds okay except for the fading in and out. Love AVC (which this doesn't have)! Not a problem if I tune to my local transmitter, though. So far, I don't hear the distortion from the detector like I hear in the 70.
RE: Philco 20 - next project - rfeenstra - 12-23-2020
Decided to add a bucking transformer. There was considerable real-estate under the chassis so I decided to add it there. Easily removable. Drops the voltage to about 106 vac to the power transformer. Radio works fine at that voltage.
RE: Philco 20 - next project - rfeenstra - 12-26-2020
I think I'm finished with the cabinet. Some may not like what I did with the trim, but oh well! I wanted to give it a bit of "character" and a little worn look so I toned it then rubbed lightly with 0000 steel wool to take a bit of toner off corners. The camera flash makes it look more pronounced than it is. Now to put the radio back in. Grille repairs turned out ok. There was a lot of loose veneer and broken "core" wood. I wish I could find the grille fabric that more closely resembles the original. Not a huge fan of the herringbone.
RE: Philco 20 - next project - MrFixr55 - 01-11-2021
This is absolutely gorgeous!! The talent found on this Phorum is amazing!
RE: Philco 20 - next project - morzh - 01-11-2021
Great looking Deluxe!
If only it could sing as beautiful as it looks
20s are not known for that.
RE: Philco 20 - next project - rfeenstra - 01-11-2021
Ya Mike, you got that right! Not a great radio. It will be a shelf queen. Since those photos were taken, the lacquer finish cracked in many locations, even on the sides where the finish was kept especially thin. Not sure what the problem is, but it may get stripped and done over. Perhaps I did not allow enough time between coats. Perhaps the cabinet moisture content was not stabilized. Not sure. I have a request for info in to Mohawk, but have not heard back.
RE: Philco 20 - next project - rfeenstra - 01-11-2021
Photos.
Maybe Russ can give me some ideas.
RE: Philco 20 - next project - morzh - 01-11-2021
Rob
Ask Kirk, he did mine. Nothing cracked. Maybe he can tell you if 20 Deluxe has peculiarities.
Speaking of the sound, 70 and some of the 90 (those with the plate detector; not all have it) sound the same.
But they do look good.
RE: Philco 20 - next project - rfeenstra - 01-11-2021
My favorite radio station is between 2 strong stations. The TRF system does not have enough selectivity to allow me to listen to the center station without a bit of bleed through from the two strong stations. And yes, there is the distortion!
RE: Philco 20 - next project - fenbach - 01-12-2021
what could go wrong? without a bucking transformer, that is. is today's higher line voltage hard on these old radios?
rfeenstra, couldn't you just use an in-line capacitor rather than a bucking transformer to reduce the line voltage?
see https://www.radiolaguy.com/info/resistance_line_%20cords.htm
RE: Philco 20 - next project - morzh - 01-12-2021
Fenbach
Are you sure you wanted to post in this thread? Not another?
RE: Philco 20 - next project - fenbach - 01-12-2021
morzh, i'm sure. in response to rfeenstra who said "Decided to add a bucking transformer. There was considerable real-estate under the chassis so I decided to add it there. Easily removable. Drops the voltage to about 106 vac to the power transformer. Radio works fine at that voltage. "
RE: Philco 20 - next project - rfeenstra - 01-12-2021
Fenbach, I have never played with the capacitor method of voltage reduction but I know others have. I've used this method in the past and had the transformer in stock so I used it. It is highly recommended to lower the voltage in, for example, a Zenith. I understand that the PT for those where not as robust as they could have been and they run warm. Taking a bit of stress off from the old PT's with aging insulation just seems like a good thing to do. Perhaps makes the tubes last longer as well.
RE: Philco 20 - next project - morzh - 01-12-2021
I asked because I never heard a cap used for a transformer radios.
With AA5 (and in the article you showed it is AA5 with the curtain burner cord) it is straightforward.
WIth the transformer it is not. Starting from the fact that when it is plugged in it could oscillate, and second unlike in AA5 where it is usedc in a circuit with stable active load, the tranformer radio becomes the load with everything taht is the load, and it is not really stable. So the dropout across the cap might vary.
And there was another thread with a curtain burner cord, so I thought you meant to popst there maybe.