03-27-2020, 12:39 PM
Hi All, I just finished up on the restoration of a Model 20 Philco radio.
I successfully restored one of these about 5 years ago.
I have a few dumb questions, first of all I replaced all block capacitors
and also the ones in the big can, using the 630 V yellow jackets, like I did
before. Also replaced any resistors that were out of spect's..
I just fired her up this morning...No smoke
But nothing else 
Here is what I done before. This set was physically in bad shape, very rusted.
The cabinet I had to rebuild the grill work.
Also the output transformer, the primary was open, and the speaker was toast.
So I got a new output transformer, the P T 291 from AES. I am using the old
field coil winding which reads 3115 ohms. I hooked the 71-A plate's from each
71A tube to the new Primary to an 8 ohm pm speaker, and the center tap to one
side of the field coil. Now the schematic says I should be getting around 190vdc.
Now is that 190 vdc to ground or to each plate of the 71A's? If it's to ground
then I'm getting about 50mv ?? Also where it the best place to get the B+ voltage
I get on the 80 rectifier and am getting 5.45VAC on the filiments and 525vdc accross
each small pins and nothing to ground. Where is the best place to read B+ voltages?
Thanks for any help,
Gary
I successfully restored one of these about 5 years ago.
I have a few dumb questions, first of all I replaced all block capacitors
and also the ones in the big can, using the 630 V yellow jackets, like I did
before. Also replaced any resistors that were out of spect's..
I just fired her up this morning...No smoke
But nothing else Here is what I done before. This set was physically in bad shape, very rusted.
The cabinet I had to rebuild the grill work.
Also the output transformer, the primary was open, and the speaker was toast.
So I got a new output transformer, the P T 291 from AES. I am using the old
field coil winding which reads 3115 ohms. I hooked the 71-A plate's from each
71A tube to the new Primary to an 8 ohm pm speaker, and the center tap to one
side of the field coil. Now the schematic says I should be getting around 190vdc.
Now is that 190 vdc to ground or to each plate of the 71A's? If it's to ground
then I'm getting about 50mv ?? Also where it the best place to get the B+ voltage
I get on the 80 rectifier and am getting 5.45VAC on the filiments and 525vdc accross
each small pins and nothing to ground. Where is the best place to read B+ voltages?
Thanks for any help,
Gary
