Circuitry; Power Supply Circuit - Olivetti ECR 7100 Service Manual

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4. CIRCUITRY

4-1 POWER SUPPLY CIRCUIT

+18V
+18V is generated using the 15.6V AC input across Pins 1 and 2 of CN1.
This AC voltage is rectified by the bridge rectifier and filtered by EC6, a 4700μF capacitor.
The resulting DC voltage is about +18V.
+P6V
The circuit generating the +6V uses the +18V. It applies to the collector of Q1, a 2SD2012 transistor.
It is also dropped across R21, a 1k ohm resistor, and ZD3, rated at 6.8V. This provided a bias
voltage of about 6.8V DC on the base of Q1.
This output voltage is filtered by capacitor EC1 and supplied the emitter of transistor Q1.
This voltage is used to the printer.
VCC, VBB
The circuit generating the +5V uses the +18V. It applies to the collector of Q2, a 2SC3242A
transistor.
It is also dropped across R22, which is a 3.3 Kohm resistor, and ZD1, rated at 6.2V. This provided a
bias voltage of about 6.2V DC on the base of Q2.
This output voltage is filtered by capacitor EC3 and supplied the emitter of transistor Q2.
VCC is through D7 from the emitter of Q2.
VBB is through D8 from the emitter of Q2.
FUSE
The fuse is AC250V T1A, it is the secondary side at transformer.
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Y110910 – 8 ECR7100 Service Manual 41