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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Mini drill control (CB8767E)
This control for 12 V drills was found in a 90s Elektor. The components are current, and Q1 can be...
AC relay for power grid (CB22174E)
Found in an old English publication, this circuit applies to the 240 V network, but can be changed to...
Gain controled shield for operational (CB8777E)
This circuit was found in a 90s Popular Electronics. With it, using a 4066, it is possible to...