Sam4s ER-390 SERIES Service Manual page 38

7 Special Circuit Descriptions
7-1 Power Circuit
7-1-1 VDISP : +30VDC
+30VAC is rectified by the bridge diode (D4,D5,D6,D7) and the capacitors(C40,C28).
7-1-2 VDRV : +24VDC
+24VDC is produced by the bridge diode (BD1) and the capacitors(C25,C7). This voltage is used as a Cash Drawer
Solenoid driving voltage and a source voltage of the other voltage sources.
7-1-3 VCC : +5VDC
+5Vdc Logic driving voltage is produced by U5(MC7805). The voltage is smoothed by C50(100uF) and then +5Vdc
Logic voltage is produced .
7-1-4 VPRT : +8.5VDC
+8.5VDC Thermal Printer driving voltage is produced by the step-down dc-dc converter U4(34063A). That is, U4
produces rectangular wave at the collector of Q10(A1010) by switching Q6 using +24VDC. This makes D3(IN5822)
and L5 store energy. The voltage is smoothed by C38(470uF) and then +8.5VDC thermal printer driving voltage is
produced .
7-1-5 VPH : +8.5Vdc
+8.5VDC Thermal Printer Head driving voltage is produced by VPH_ONOFF signal of CPU and the related
Circuit(Q11,Q16,Q17) on Main PWB. The Source Voltage is VPRT (8.5V).
7-1-6 VBT : +3.6Vdc(Min)
The Source Voltage is VCC(5V). When AC Power is off, VBT is supplied to SRAM, RTC for saving the data.
7-2 SAM4S ER-390 SERIES