erik fiss | galleries | Yashica Electro 35 Repair Manual

When the shutter-release switch reaches the bottom of its stroke, it connects the timing capacitor C1 to the circuit. Also, the shutter releases and the blades move to the open position. Transistor TR1 remains turned off while the timing capacitor charges to the required voltage. Consequently, transistor TR4 conducts current through the electromagnet. The electromagnet holds its armature to keep the blades in the open position. The time it takes for the timing capacitor to charge depends on the resistance of the CdS cell. When the timing capacitor reaches a sufficient charge, the voltage on its positive plate turns on transistor TR1 -- this trigger voltage depends on the diaphragm setting Which determines the resistance in the emitter circuit of TR1. TR1 turns on TR2, and TR2 turns on TR3. Now, TR3 robs transistor TR4 of the base current it needs to conduct. TR4 shuts off, depriving the electromagnet of current. As the blades close, the blade operating ring closes the capacitor shorting switch S3. S3 opens as the blades open and closes as the blades close. So the time that S3 opens determines when the timing capacitor can start accepting a charge. The eccentric adjustment on S3 is your high-speed adjustment point.