Note
Single conversion superheterodyne circuit.
Essentially the same radio as the S-40A, but using new miniature IF transformers and a new tube line up. The S-40BU uses the universal power transformers for 120-240 VAC operation. It also adds one megahertz of additional coverage on the high end. There are some minor cosmetic differences.
Features include a headphone jack, BFO, ANL, AVC, mute, built-in speaker, three position tone control, sensitivity control, and an xero to 100 bandspread.
Coverage: 540 kHz to 44 MHz
IF: 455 kHz
Modes: AM, CW
BFO
ANL
AVC
Uncalibrated Bandspread
Audio output: 1 watt, 3.2 Ω
Power (S-40B): 120 VAC, 75 watts
Power (S-77): 120 volts AC-DC
Tubes: (8 total): (1) 5Y3, (1) 6K6, (1) 6H6, (1) 6SC7, (2) 6SK7, (1) 6SA7, (1) 6SG7