Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
For many years
now I have been scanning
and posting Radio Service Data Sheets like this one featuring the Colonial Model 652, 5-tube broadcast
short-wave superheterodyne radio receiver for many years now. There are still many people who restore
and service these vintage radios, and often it can be difficult or impossible to find schematics and/or
tuning information. The thumbnail image of a real-life
Colonial Model 652 was
found on the radiomuseum.org website.
Colonial Model 652 5-Tube Broadcast-Short-Wave Superhet Radio Service Data Sheet
The tubes and their functions are: 6A7- Oscillator and Det.
1; 78-I.F.; 75-A.V.C.-Det. 2-A.F. 1; 42-output A.F. 2; 80-rectifier.
In order to prevent interference from 600- meter code stations, when the receiver is located near
the coast, a wave-trap is incorporated in the antenna circuit. Although this trap is shown in the diagram
as a coil with a condenser (L-C), actually it consists of two multi-layer coils wound on top of each
other with one end of' each coil unconnected.
The voltage drop across the 0.5-meg. volume control, due to the diode current of the 75 tube, is
used for A.V.C. voltage.
Alignment Procedure
The I.F. Stages: (1) Set the service oscillator to 450 kc. and tune the R.F. transformers. (1) Couple
test oscillator to green antenna lead, leaving antenna connected. (2) Set the service oscillator to
1,560 kc. (3) Screw the oscillator padder condenser to approximately three-fourths maximum capacity.
(4) Turn tuning condenser all the way out. Adjust oscillator trimmer for maximum output. (5) Set the
service oscillator to 1,400 kc. and tune in its signal. Then adjust the Vl trim-mer. on the variable
condenser nearer the dial, for maximum output. (6) Set service oscillator to 600 kc. and tune in its
signal. Then slowly rotate variable condenser and adjust padder.
Posted February 2, 2017
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...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
