Sparton 409 (409GL) "Seven-Sided" Blue Mirror Radio (1938)
The 409GL was the last in the line of the Sparton Blue mirror radios. It is similar in design
concept to the Bluebird 506/566 models in that it consists of an inclined mirror with the
electronics housed in a rear cab. The mirror is seven sided in "midnight blue", with beveled
edges and a cut-out for the speaker. The two feet are in black lacquer. It is a surprisingly small
radio, measuring approximately 12" wide (mirror tip to mirror tip), 7.5" high and 5" deep. It was
originally intended as a second radio for the home, with a selling price of less than $20.
The rear cab is finished in grey and contains a 4-tube super-heterodyne receiver together with
ballast tube and resistance line cord. The tube line up is 6A8GT (mixer/LO), 6J7GT (2nd
detector), 25L6GT (power output), 25Z6GT (rectifier) and BK3AJ (ballast). The line-cord and
ballast tube are series connected with the tube filaments. The manufacturer recommended the
use of an external antenna with this radio, comprising 50' of wire at a height of 25 to 50'.
concept to the Bluebird 506/566 models in that it consists of an inclined mirror with the
electronics housed in a rear cab. The mirror is seven sided in "midnight blue", with beveled
edges and a cut-out for the speaker. The two feet are in black lacquer. It is a surprisingly small
radio, measuring approximately 12" wide (mirror tip to mirror tip), 7.5" high and 5" deep. It was
originally intended as a second radio for the home, with a selling price of less than $20.
The rear cab is finished in grey and contains a 4-tube super-heterodyne receiver together with
ballast tube and resistance line cord. The tube line up is 6A8GT (mixer/LO), 6J7GT (2nd
detector), 25L6GT (power output), 25Z6GT (rectifier) and BK3AJ (ballast). The line-cord and
ballast tube are series connected with the tube filaments. The manufacturer recommended the
use of an external antenna with this radio, comprising 50' of wire at a height of 25 to 50'.
After purchasing this radio, I discovered that the original tubes had been replaced with 35Z5GT,
50L6GT, 12A8GT and 12J7GT, all having 0.15A filaments. The originals were 25Z6GT, 25L6GT,
6A8GT and 6J7GT with 0.3A filaments. It turns out this was a neat idea, since the substitution
allowed the troublesome resistive line-cord to be disconnected, a definite safety enhancement!
Other than filament characteristics, these two tube sets are interchangeable without any circuit
modifications other than the bypassing of the potentially dangerous line cord and the removal of
one connection from the socket of the 35Z5GT. Furthermore, for the vintage radio purists, the
original configuration may be quickly restored by replacing the original tube types and
re-connecting both the line cord (which is still present) and the wire to the rectifier socket.
It is interesting to note that the tubes now in this set were not available until a year or two after
this radio was manufactured, once the "all American Five" (AA5) line-up had been established.
Had they been available at the time of manufacture, it's highly likely these would have been used
in preference to the original types.
50L6GT, 12A8GT and 12J7GT, all having 0.15A filaments. The originals were 25Z6GT, 25L6GT,
6A8GT and 6J7GT with 0.3A filaments. It turns out this was a neat idea, since the substitution
allowed the troublesome resistive line-cord to be disconnected, a definite safety enhancement!
Other than filament characteristics, these two tube sets are interchangeable without any circuit
modifications other than the bypassing of the potentially dangerous line cord and the removal of
one connection from the socket of the 35Z5GT. Furthermore, for the vintage radio purists, the
original configuration may be quickly restored by replacing the original tube types and
re-connecting both the line cord (which is still present) and the wire to the rectifier socket.
It is interesting to note that the tubes now in this set were not available until a year or two after
this radio was manufactured, once the "all American Five" (AA5) line-up had been established.
Had they been available at the time of manufacture, it's highly likely these would have been used
in preference to the original types.
 | |  | |  | |  | |  | |  | |  | |  | |  | |  | |  | |  |
Copyright TubeRadioLand.com