Photometer for enlarger (CB8342E)

This circuit for old photo enlargers was found in a 1970s RCA manual. The components are from the time, but modern equivalents can be used.

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Unijunction Oscillator (CB4431E)
This is the traditional unijunction transistor relaxation oscillator circuit for the audio band. The...
4-channel system Amplifier (CB24168E)
This is half of a 4-channel amplifier from a system published in the October 1971 issue of Radio...
Crystal dipper and oscillator (CB23926E)
This circuit works both as a grid-dip (transistorized) and as an oscillator. The circuit is from a...