erik fiss | galleries | Yashica Electro 35 Repair Manual

Depressing the release button a little further connects the yellow lamp L2. Lamp L2 turns on when the light conditions are so dim that a shutter speed slower than 1/30 second is required. The resistance of the CdS cell is then high. The high resistance of the CdS cell keeps transistor TR1 turned off -- the voltage dropped across R5 is too low to trigger the transistor. Consequently, transistors TR2 and TR3 are also turned off. As long as transistor TR3 is turned off, transistor TR4 conducts. And the current flowing through transistor TR4 also flows through the yellow lamp L2.