General Electric (GE) H-500 Bakelite Table Radio (1939)
This standard-broadcast receiver from 1939 is referred to by collectors as the "turbine" radio. GE has long been
a manufacturer of heavy industrial equipment, including turbines for power generation, so this is fitting.
The H-500 photographed here is one of a family
of similar receivers that includes H-501, H-510,
H-511, H-520 and H-521*. In addition to the
brown bakelite model shown, which GE referred
to as having an "oak" finish, each of these family
members has W and X color variants. W
represents an ivory finish (plaskon) and X an
"onyx" finish (beetle plastic).
The 510, 511, 520 and 521 models each had
push-button tuning in addition to manual (which
uses the thumbwheel knob), while the H-520 &
521 also featured a "beam-o-scope" antenna
attachment and a moulded plastic back instead
of cardboard. The 501, 511 and 521 models
differed from the 500, 510 and 520 in that they
incorporated safety upgrades (minor circuit
modifications) necessary for isolating the chassis
from the supply line in order to satisfy the
requirements of the Underwriters Laboratory.
The H-500 shown has tube line-up 12A8GT,
12SK7, 12SQ7, 35L6GT and 35Z5GT. Later
production would use a 12SA7 tube in place of
the 12A8GT. It is interesting to note that a
35L6GT tube was used rather than the 50L6GT
more commonly used a little later in the Octal
AA5 era. I conjecture that this was a result of
these tubes being introduced to the market at
about the same time as the radio; the 50L6GT
appeared about 2 months later than the 35L6GT
and may have just missed the cut for this design.
Similar factors may have influenced the initial
choice of 12A8GT versus 12SA7. A dropper
resistor was used to adjust the line voltage to
match the sum of the filament voltages. The
schematic is found here, courtesy of NostagiaAir.
*Source: Riders Manuals, Volumes 10 and 11.