Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
I have been scanning and posting Radio Service Data Sheets like this one featuring the
Stromberg-Carlson Nos. 230 and 231 Series 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. This 231R version is unique with
its half-round configuration meant to sit at the side if a sofa or chair
(click on thumbnail for more info). It could pass today as a room humidifier. A running list of all data sheets
can be found at the bottom of the page to facilitate
a search.
See Tom Bavis' AudioPhool.com website for an extensive collection of
Stromberg-Carlson photos, datasheets and Sam's Photofacts files.
Stromberg-Carlson Nos. 230 and 231 Series
Intermediate-Frequency Adjustments. The intermediate frequency used in these
receivers is 465 kc. In making these circuit adjustments always align the circuits
in the order given in these instructions.
(1) Operate the "Range" switch of the receiver to the "Autorange position. Set the receiver's
tuning dial at its extreme low-frequency position, and operate the tone control knob to the "normal"
position. Rotate the volume control knob to its maximum clockwise position; (2) Apply between the
chassis and the control grid of the 6A8 tube, a modulated signal of 465 kc. from a good test
oscillator, using a 0.1-mf. condenser in series with the signal lead. Do not remove the control-grid
lead connecting to this tube; (3) Now align the I.F. circuits in the following manner: Secondary of
2nd I.F.; primary of 2nd L.F.; secondary of 1st L.F.; primary of 1st I.F.; adjusting the circuits to
obtain maximum reading on the output meter, reducing the output of the test oscillator as required.
Alignment of "C" Band. In aligning the R.F. circuits for this range, replace the 0.1-mf.
condenser which was placed in series with the test oscillator's output lead for the L.F. alignments,
with a 400-ohm carbon resistor. This lead should then be connected to the antenna binding post. (1)
Operate the range switch on the receiver chassis to the "C" position, and set the test oscillator's
frequency and the receiver's tuning dial to 17 megacycles; (2) Adjust the oscillator's "C"-band
trimmer for maximum output; (3) ;Adjust the antenna's "C"-band trimmer for maximum output, at the
same time rock the gang tuning condenser back and forth, through resonance, until maximum output is
obtained.
Posted December 27, 2016
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.
