[joybird]

Working on 41-290-121
Plainly stamped on chassis

Question

The 2nd Det and AVC tube is shown as 7A6 for this chassis

I received the radio with a 7C6 in place of it and it plays well (before alignment)

I inserted a NOS 7A6 and hear NO difference.

What is up with this chassis.

Tubes are not the same , so what is the purpose for Philco to stick a 7A6 in a 41-290-121 chassis
Other versions use a 7C6.

Puzzled

Bob T

[Ron Ramirez]

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:

Click here for 7A6

Click here for 7C6

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.

[joybird]

Hi Ron

Thank you for jumping in.
I agree my favorite Tube Data source also.

Schematic http://www.radiomuseum.org/r/philco_41_290.html


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.

Bob T

[joybird]

Got it

The Terminal Strip for the Antenna on Back of Radio

1-4

Thanks to Tom Forbes Memory  

Bob T