03-19-2017, 07:51 AM
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.
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.
--
Ron Ramirez
Ferdinand IN
