1 . Metering circuit

 

    Metering circuit from the VT1, VT2 and other components, metering devices using cadmium sulfide RG (Cds) photoresistor . The power switch K1 is set to " 2" position , gently press the shutter button to stop half- stroke , photometric switch K2 is closed shutter release plate linkage , metering circuit to work . If the subject is dark scene reflected light , RG resistance greater power through the metering sensitivity adjustment potentiometer RP and RG partial pressure , so VTl base voltage greater than 0.7V, its emitter junction is forward biased and saturated conduction LEDl light ( red ) , suggesting that low light photography , the need to adjust the aperture , shutter speed or use flash fill light shooting. At this time , VT2 off , LED2 is off ; Conversely , if the RG to the sensed reflected light is bright , the cutoff VTl , VT2 conduction , LEDl is off , LED2 ( green ) light, can shoot tips .

 

    2 . Flash circuit

 

    VT3, C1, T1 etc. three-point oscillator circuit inductance complete low voltage DC → AC → DC high voltage high voltage conversion , the flash power . DC bias resistor R3 VT3 's , TI 's junior Ll , L2 is positive feedback coil , L3 is the high voltage output coil , LED3 charging indicator tube ( yellow ) .

 

    The Kl set to " 3" position , VT3 will start-up , an oscillation frequency of 8kHz 12kHz. Oscillation signal by L3 boost , VDl (1A, lkV) rectifier for charging the storage capacitor C2 , and R4 is triggered by charging the capacitor C3 . When the voltage across C2 up to about 300V, charging is completed , VT3 is saturated , the oscillation stop , LED3 light , indicating that the flash can be photographed . At this time the shutter button is pressed to stop the whole trip , open the shutter blades to about 85% of the light bar area, the flash switch K3 is closed linkage , C3 through K3, trigger transformer T2 primary rapid discharge , T2 secondary induction of about 6kV pulse pressure, so that the lamp inside the XE xenon ionization charge conduction , so C2 through discharge lamp ( flash ) . After the shutter is released , K3 off , LED3 extinguished , VT3 re- start-up , start a new round of oscillation and the charging process , to prepare for the next flash shooting .

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