Circuitry; Power Supply Circuit - Olivetti ECR 7900 Service Manual

3. CIRCUITRY

3-1 POWER SUPPLY CIRCUIT

+VDRW
+VDRW is generated using the AC input across pins 3 of CN12. This AC voltage is rectified by D15,
a 1SR154 diode. The resulting DC voltage is about +24V. This voltage is used by the drawer
solenoid and the buzzer.
VCC5
VCC5 is generated using the 13V AC input across pins 1 and 2 of CN12. This AC voltage is rectified
by the RS402 bridge rectifier and filtered by EC14 a 15000uF capacitor.
The resulting DC voltage is about +12V. It is supplied to the input of U9, a M5291 comparator and
then it outputs +5V.
VCC3, VBB
VCC3 and VBB are generated using the VCC5. VCC5 is supplied to the input of U15, a
BA00CC0WFP regulator and then it outputs about 3.6V.
After 3.6V passes through D12, it becomes 3.3V as VCC3.
After 3.6V passes through D13, it becomes 3.3V as VBB.
VPRN
VPRN the printer motor voltage is generated using the 13V AC input across pins 1 and 2 of CN12.
This AC voltage is rectified by the RS402 bridge rectifier and filtered by EC14 a 15000uF capacitor.
The resulting DC voltage is about +12V. It is supplied to the collector of Q10, a 2SD1415 transistor.
This base voltage is controlled by ZD7. This emitter voltage is about +7.6V.
-VPW
The –VPW circuit uses 26.5V AC across pins 4 and 5 of CN12.
This AC voltage is rectified by D4, a 1SR154 diode and filtered by EC13.
The resulting DC voltage is about -30V. It is supplied to the collector of Q12, a 2SA1284D transistor,
and base voltage is controlled by ZD8.
-VPW is approximately -28V DC. This voltage is used by the display.
VF
The filament voltage, VF1, VF2 are used by the display tube.
Its AC input is 4.3V, and uses a ground reference -23V from the -28V circuit dropped across ZD9
and R181, R182, a 470 ohm resistor.
Fuse for Secondary side.
F1 250V 1.6A
F2 250V 3.15A
F3 250V 1.6A
F4 250V 1A
F5 250V 500mA
Y108540-8
TR-5 19370 1.6A
MRT3.15A
TR-5 19370 1.6A
TR-5 19370 1A
TR-5 19370 0.5A
ECR 7900 Service Manual 21