[keith49vj3]

All, I picked up a Philco 50-925 for a couple of dollars so I could demo sweep alignments for folks in my radio club.  This radio has not been worked on before with the exception of the 4 antenna wires in the cabinet and the blue wire going to the top of the tuning cap that had been cut.  The cabinet loop antenna has four leads and none have continuity between them.  These attach somewhere on the four post terminal strip shown in the photo below.  There is a green wire on what I have labeled terminal C that connects to the high side of the audio transformer secondary.  This is not shown in any of the available schematics but is visible on the SAMs photofact and other pictures I've found online.  I haven't found any information on how the loop antenna connects to the radio.  I did attach a long wire antenna to the terminal I've got marked "A" and can pick up a few AM stations.  For those that have a subscription to radiomuseum the SAMS and Rider schematics can be found here radiomuseum schematic.  Antique Electronic supply also has the schematic posted here schematic.  Can anyone help me figure out these connections?  What's with the high side of the audio transformer going to terminal C? 
Help!
Keith            

[keith49vj3]

I forgot to mention that the IF and audio stages for AM work and FM plays great. Really confused by the antenna set up.
Keith

[keith49vj3]

Shoot, just realized that the blue wire connecting to the top of the tuning cap can't go to terminal D since that's on the wrong side of L4 so this must go somewhere else.

[RodB]

C is for an external speaker.

[keith49vj3]

Thanks Rod, That makes perfect sense. Is there a way to edit my post? It's a Philco 50-925 and not a Philco 50-295. Did Philco ever produce their own service info or did they farm it out to Riders and SAMS? Should there be continuity between the four antenna wires? There is a low resolution photo of the top of the radio chassis on the radiomuseum website. The photo appears to show two wires going to "A", on wire going to "B" and the forth going to the tube of the tuning condenser. But its not clear what attaches to D.
Getting closer.
Keith

[462ron]

Hi Keith, here is the official Philco service info found in the Philco Library under service info……https://philcoradio.com/library/download/service%20info/yearbooks/1950/split/Part12-Philco%20Home%20Radio%20Yearbook%201950-final.pdf

Ron

[GarySP]

Hello Keith! I've updated your thread with the proper model number. Take care, - Gary

[RodB]

Most loop antenna setups are either one continuous loop with two connections or 2 loops with 4 connections. The latter can be considered an rf transformer with the primary winding capabile of attachment to an external antenna, the secondary to the rf amp tube. So, you should get continuity on one pair and continuity on the other. In addition the antenna is usually used for a path of the AVC connection to the grid of the rf amplifier. The link that Ron provided above has this clear example of your antenna.

SAMs and Riders came after the fact and I believe they worked with most manufacturers to get their info. At times there's no way they would be able to know all the makers of radios. Beitman Supreme Publications are another source though they don't have complete coverage of all models, as they publish *the most popular schematics". Their diagrams are usually very clear but limited to just the schematic and sometimes alignment data.

[keith49vj3]

Finally, got the antenna fixed (repaired some broken wires) and have the radio playing. I've got four different schematics all with differences in the antenna circuitry. Mine must be from the first run.
Thanks everyone.
Keith

[radiorich]

Hello Keith,
great news !!

Sincerely Richard