Motorola B3-1E AM/FM Radio (1960)
December 18, 2016
Kihwal Lee, K9SUL
It is a typical AC/DC radio, but is a bit unusual radio in that the audio power amp is 50C5 push pull. It sounds great and has ample volume.
HCC85 17.5V heater dual triode, FM RF amp, converter (output 10.7MHz)
12BA6 1st IF amp 10.7
12BA6 AM IF (455kHz) amp, 2nd FM IF amp(10.7)
12BE6 AM converter
12AU6 FM limiter, AM detector
12AL5 FM ratio detector
12AX7 AF amp, phase inverter
50C5 Two for PP audio amp
The tubes are all marked as Motorola. The actual manufacturer is RCA. Only the 12AX7 needed to be replaced. I also added a fuse. The circuit is built on a thick double sided printed circuit board with through hole plating.