Open the machine cover. Electricity observation aperture no action that aperture ring cannot automatically open. Check the light ring plate deformation, it also without dust; Check aperture motor driven tube Q701 each voltage, found the c, b, e voltage of 5 v respectively, 0, 0 v v, illustrate Q701 bias circuit fault. Q701 bias voltage by the output voltage by R725 IC704 7 feet, the measured potential IC704 7 foot is about 2.3 V (normal), that is not R725 open, is the b and e Q701 breakdown. jc4service manual download site
 jc4service manual download site
Check Q701, R725 respectively, found desoldering K725 a pin. After welding, troubleshooting.jc4service manual download site