Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
National Union
Radio Corporation, located in Orange, New Jersey, had been producing radios
since its formation in 1929 when this Radio Service Data Sheet for its Model
G-619 "Presentation" tabletop set appeared in a 1947 issue of Radio-Craft
magazine. That they survived the
Great Depression which began in the year of
their founding is a testament the tenacity of its management, design staff, and
production workers. This 5-tube radio had a very nice mahogany case with a
unique reverse-lettering dial glass plate. A few years ago I posted an
advertisement by Union Radio from a 1945 issue of Radio-Craft appealing
specifically to
women
engineers and technicians because of the severe shortage of men available
while serving in the armed forces during World War II.
Radio Data Sheet 344 National Union "Presentation" Radio Model G-619
Circuit:
Superheterodyne - Tuned r.f. stage - a.v.c
Tuning:
Broadcast Band
Power Supply:
105-125 volts, 60 cycles
105-125 volts, direct current
Approx. 30 watts consumption
Preliminary
(a) Adjust the DIAL POINTER along the dial cord to the position opposite the
first right-hand punch mark on the dial backing-plate, with the tuning condenser
gang completely out of mesh (Minimum Capacity); (b) Set VOLUME CONTROL to the
FULL ON position; (c) Maintain SIGNAL GENERATOR output at MINIMUM consistent
with a readable Output Meter indication; (d) OUTPUT METER across voice coil; (e)
Follow sequence indicated below.
Service Notes
Hum Modulation:
On Early Production runs Condenser C-18 consisted of two .05 uf units. One ground
terminal was connected to CHASSIS, the other to B-. Disconnect the CHASSIS terminal
of the .05 Condenser now connected to Pin No. 1 of the 12SA7GT tube and connect
this lead to Pin No. 5 of either of the 12SK7GTs or to any other convenient B-point.
This effectively bypasses the a.c. modulation hum to B- instead of to chassis.
Oscillation:
Remove one side of Resistor R-2 (in grid circuit of 12SA7GT) now connected to
a.v.c. bus and reconnect to cathode No.5 pin 1 of i.f. -12SK7GT
Reinstalling Chassis (After Alignment):
(a) With chassis still on the bench, set dial pointer at the minimum capacity
end of travel.
(b) Slide chassis into cabinet and adjust its position so that the dial pointer
is opposite and in line with the FIRST calibration mark at the right-hand end of
the GLASS DIAL SCALE.
(c) Tighten the chassis hold down screws.
(d) Tuning should now track so that peak signal is attained at the proper frequency
calibration on the glass dial scale.
Radio Service Data Sheets
These schematics, tuning instructions, and other data are reproduced from my
collection of vintage radio and electronics magazines. As back in the era, similar
schematic and service info was available for purchase from sources such as
SAMS Photofacts, but these printings
were a no-cost bonus for readers. There are 227 Radio Service Data Sheets as of
December 28, 2020.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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and text used on the RF Cafe website are hereby acknowledged.
