This is the 1968 MR480 commercial cassette recorder circuit. The circuit was fully transistorized and powered by 4 large batteries. We found the diagram in a Japanese documentation of the time.
This circuit is a kind of Hertz Loop that can be used to check the operation of transmitters and...
This circuit, with printed circuit board included, is from a Radio Electronics magazine from July...
The basis of this circuit is 1/4 of a 4136 integrated circuit which consists of a quadruple 741....