Why did they add a 7A6 to the 41-290 (and 41-285, 41-287, 41-255)?
Answer: To increase the advertised tube count.
More tubes means better performance, right?
Not necessarily.
In the 41-280 (and 41-250), a 7C6 performs the jobs of 2nd detector, AVC, and first audio amp. In the other models mentioned, Philco split the task between a 7A6 and 7C6. A 7A6 is a dual diode (only), while a 7C6 is a dual diode and triode in the same envelope.
Looking at tube diagrams for the 7A6 and 7C6 in my favorite online tube data guide:
you can see that one set of diodes of the 7A6 lines up with one set of diodes of the 7C6. If a 7C6 is plugged into the 7A6 socket, there is an anode at pin 6 and cathode at pin 7 that will work. The other 7A6 diode has anode at pin 3 and cathode at pin 2. In the 7C6, pin 3 is triode grid and pin 2 is triode plate, so this may not work connected as a diode.
The Radio plays well no difference whether a 7A6 is used or a 7C6 is. I have left the 7A6 in as that is what the chassis calls for.
If I leave NO tube in that Position, Radio Plays but reduced Volume.
Now I want to check the IF alignment
Instructions state
High side of sig gen to No 4 terminal loop panel (WHERE IS THAT?)
I checked Bitman's, Riders, and Radio Museum Nothing showing what No 4 Terminal loop panel is or where it is.
You are correct about the Rubber wire.
Owner does not want to spend $$$$$$ to replace it all Sooooo.
Radio Plays well and I did replace any rubber falling apart. Had to rewire Lamp sockets as they were Rubber too.
I gave my Philco 41 Manual to Tom Forbes, that may have more info on this chassis.
Tom hard to contact.
