Fairbanks-Morse 9-Tube All-Wave Model 91 Superhet. Chassis
November 1936 Radio-Craft

November 1936 Radio-Craft [Table of Contents] 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 Fairbanks-Morse 9-Tube All-Wave Model 91 Superheterodyne Chassis 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 the Fairbanks-Morse Model 91 is from the 9KUW website. I could not find a complete model.

Fairbanks-Morse 9-Tube All-Wave Model 91 Superheterodyne Chassis

These voltages are measured from the tube socket prongs to ground. Alignment should be made with the volume control of the receiver on full, and any attenuation made with the gain control of the test oscillator. Align the LF. stage at 456 kc. and the tuning con-denser set at full mesh, band switch on broad-cast position. The lead to the set from the test oscillator is connected to the cap of V2 through a condenser. Adjust all trimmers to the highest possible output. Turn the receiver dial to 1,500 kc. and connect the test oscillator to the receiver antenna lead through a 200 mmf. condenser. Adjust the B.C. oscillator trimmer for highest output, then adjust the detector and R.F. trimmers likewise. Tune to 600 kc. and adjust the B.C. band series padder to highest output, while rocking the tuning condenser to the best position. The next band is adjusted the same way at 5.4 mc. and 1.8 mc. The dummy an-tenna for this band is a 400-ohm carbon resistor in series with the antenna leads.

Posted January 20, 2017