Philco 41-290-121 Chassis !!!!!! RON ? - Printable Version
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+--- Thread: Philco 41-290-121 Chassis !!!!!! RON ? (/showthread.php?tid=16394)
Philco 41-290-121 Chassis !!!!!! RON ? - joybird - 03-18-2017
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
RE: Philco 41-290-121 Chassis !!!!!! RON ? - Ron Ramirez - 03-19-2017
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.
RE: Philco 41-290-121 Chassis !!!!!! RON ? - joybird - 03-19-2017
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
RE: Philco 41-290-121 Chassis !!!!!! RON ? - joybird - 03-19-2017
Got it
The Terminal Strip for the Antenna on Back of Radio
1-4
Thanks to Tom Forbes Memory
Bob T