If an output transformer is present on the chassis, and has one of its primary wires connected to pin 3 of the 35L6 tube, then its secondary wires should be connected to the speaker. If the output transformer is mounted on the speaker, then its secondary wires are probably already connected to the speaker. Its primary wires are all which you need to connect. One should go to pin 3 of the 35L6 tube (this is the output tube, and pin 3 is the plate pin of this tube). If one wire is red and the other is blue, common practice has the blue one connected to pin 3 of the 35L6. The remaining primary wire should be connected at point D in the schematic. This point is after a resistor which connects to pin 7 of the 50Z7 tube (this is the rectifier tube, and pin 7 is the cathode of this rectifier).
Now regarding tube sockets (just in case you don't know), when you are looking at the underside of the chassis, and the tube key is facing you (the fat pin in the center of the base of the tube with a nub on it--the nub is the key), pin one is to the left of this key. The pin numbers progress clockwise around the base of the tube, and end on eight to the right of the key. If you are looking down at the top of the chassis (which isn't usually very useful if you are trying to make wire connections underneath the chassis), pin one is to the right of the key, and pin eight is to the left.
Thomas
I think that the shielded cable is for your phonograph cartridge, as everyone else on here seems to agree on. I will look at your pictures that you sent me to-morrow, after school. If you do not have an output transformer for your speaker, go to Radio Shack and see if they have any P.A. line matching speaker transformers. The transformers will have high impedance primary taps marked in wattages, and secondaries marked in speaker impedances. Simply hook the appropriate secondary to your speaker (in this case 8 ohms). Hook the C primary lead, which stands for common, to the point marked D in the schematic, as I explained before. Start with the lowest wattage terminal and hook this to pin 3 of the 35L6 tube. This terminal should have the highest resistance when measured between it and the C terminal with your ohm meter. Test operation (that is, if your radio is otherwise in operating condition). Try each higher wattage terminal until optimum power and tonal quality is achieved as well as appropriate voltage on the plate of the output tube. When you achieve this, you may continue to use whichever wattage terminal that works best. You may also purchase a universal single ended output transformer from www.tubesandmore.com, but if you can get a P.A. transformer from Radio Shack, this will be more convenient, and will work just as well. When purchasing a transformer from www.tubesandmore.com, you only need one capable of handling 3 watts, though if there is a higher wattage UNIVERSAL type output transformer which is less expensive, go for that instead. Usually price increases with wattage increase.
Thomas
The plug you show with the shielded wires will be your phonograph plug if some of the wires goes to the selector switch. One of the switches will connect to the phonograph wire(s) when the switch is turned to phono. Any ceramic cartridge can be used fairly successfully. Proper matching is achieved with the right condenser/resistor combination, if necessary. You do not need this matching, but audio may be harsh without it. Without knowing what a specific cartridge requires, you cannot know what to use. I could honestly only tell you what the best combination is if I experimentally hooked it up myself, as it also depends upon the radio amplifier and your personal preferences. A magnetic cartridge will work if equipped with a pre-amplifier.
Thomas
Thomas