HP LaserJet 1100 - Page 42

EN Functional Overview
: Engine Control Unit (ECU)/power system
42
Power system on ECU
The AC, DC, and high-voltage power supply circuits are all contained within the ECU.
AC power distribution
The AC power circuitry supplies AC voltage whenever the power cord is connected to
the AC power source. AC voltage is distributed to the DC power supply circuitry and to
the AC driver circuitry, which controls AC voltage to the fusing assembly's heating
element.
DC power distribution
The DC power distribution circuitry, located on the ECU, distributes +3.3 V DC, +5 V
DC and +24 V DC as follows:
Overcurrent/overvoltage
There are two overvoltage devices in this printer:
• Fuse F101 provides overcurrent protection for the fusing system circuitry. To
check or replace the fuse requires the removal of the ECU. Fuse F102 (found only
on 110V units) provides overcurrent protection to the printer DC power supply
circuitry.
• In addition, the +24V DC, +3.3 V DC, and +5V DC power circuitry contains an
overcurrent protection circuit which automatically shuts off the output voltage
when an overcurrent condition occurs due to a short or abnormal voltage on the
load side.
DC power distribution
+3.3 V DC Formatter
Laser/Beam Detect Circuitry ECU
+5 V DC: Formatter
Photosensors
ECU
Laser/Beam Detect Circuitry
+24 V DC: Motor
Laser Scanner Motor
Document Scanner Motor
Solenoid
Formatter
+24VA DC: High Voltage Power Supply