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Crosley Roamio Automotive T.R.F. Receiver Models 90, 91 and 92
Radio Service Data Sheet
April 1933 Radio-Craft

April 1933 Radio-Craft

April 1933 Radio Craft Cover - RF Cafe[Table of Contents

People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.

As in the past, I am posting these Radio Service Data Sheets as a service to someone who might be doing research on vintage radios and/or restoring one. Roamio is not producing automobile radios anymore, but they do now make TiVo recorders and streaming media players. The Crosley Roamio Automotive T.R.F. Receiver Models 90, 91 and 92 was made in the early 1930 at a time when cars and trucks were just starting to experience such luxury. Crosley did not begin manufacturing its own line of cars until 1939, so none of these radios made it into Crosley autos.

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.

Crosley Roamio Automotive T.R.F. Receiver Models 90, 91 and 92 Radio Service Data Sheet

(The T.R.F series of Crosley Roamio sets; Radio Service Data Sheet No. 88 describes the superheterodyne series.)

Model 90

Crosley Roamio Automotive T.R.F. Receiver Models 90, 91 and 92 Radio Service Data Sheet, April 1933 Radio-Craft - RF CafeAverage operating potentials are given below. These values are measured with the reproducer connected and the tubes in place. For plate and grid voltages, use a high-resistance meter; measure from tube element to negative filament.

The A. V .C. potential is derived as the drop across R2. With increased signal, more current flows through the plate circuit of the combination detector and A. V. C. tube, V3, increasing the drop across R2 and thereby increasing the bias voltage applied to the control-grids of V1 and V2. This results in a reduction of the R.F. amplification, and thus maintains constant the A.F. output determined by the setting of R1.

Battery D supplies plate potential for V3. The negative "B" and positive "C" lead returns to the center-tap of two 25 ohm resistors, to secure the same plate potentials regardless of whether the car-battery positive or negative terminal is grounded.

Model 91

Average operating potentials are given in the tabulation below. Measure, with a high-resistance meter, to the negative filament contact.

*With volume control "off."

If a signal of sufficient strength is received to cause current to flow in the grid circuit of V3 (biased by R6), the resultant drop across R2 decreases the amplification of V1, V2. Resistors R3, R4, R5 are R.F. filters.

Manual volume control R1 determines the A.F. input to the control-grid of A.F. amplifier V4.

Model 92

Operating potentials appear in the table.

The circuit is adjusted for zero current flow in the circuit of A.V.C. tube V6, with normal signal input; at the same time resistor R3 establishes the normal bias required by the control-grids of V1, V2. Now, an incoming signal of increased strength causes diode V6, in conjunction with load-resistor R2, to develop across R2 an increased D.C. negative potential which reduces the amplification of V1, V2. Resistors R4, R5 are R.F. filters.

The A.F. input to the first-A.F. tube, V4, is determined by the setting of the manual volume control, R1.

Manual volume control resistor R1 has a value of 0.3-meg. Since Crosley Service Bulletin No. A8 does not include the tube operating voltages for the model 92, estimated values are given.

At the present time there are no Roamio models 93 or 94 receivers.

 

 

 

 

Posted January 28, 2015

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