Xerox 3150 - Phaser B/W Laser Printer, Service Manual

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Summary of Product
4-10
4.3.4 SDRAM
Used as a swath buffer, systems working memory area, etc. when printing.
■ Capacity: 32 MB, expandable up to 144 MB
■
Optional Additional DIMM : 16 MB / 32 MB / 64 MB /128 MB
■ Type : SDRAM 100 MHz/133 MHz, 16bit
4.3.5 Sensor Input Circuit
4.3.5.1. Paper Empty Sensing
The Paper Empty sensor (Photo Interrupter) on the engine board is monitored by the CPU. When the tray is empty the
printer flashes the red error LED.
4.3.5.2. Tray 1/MPT Sensing
Presence of paper in Tray 1 is detected by the MP sensor (photo interrupter) on the frame. The CPU monitors this
sensor to recognize paper in Tray 1, and paper is fed if there is paper present.
4.3.5.3. Paper Feeding
When paper passes the actuator on the feed sensor, it is detected by the photo interrupter. The CPU monitors the
signal and starts the process of creating the image after a specified delay time. If the feed sensor is not detected within
one second after paper is fed, a paper jam0 occurs. (red error LED is lit).
4.3.5.4. Toner Remaining Sensing
The printer does not have a toner remaining sensor.
4.3.5.5. Paper Exit Sensing
This detects that paper exits cleanly from the printer using an exit sensor on the engine board and actuator on the
frame. The CPU detects the on/off time of the exit sensor and normal operation or a jam status is reported. If a Jam2
error occurs, the red error LED is lit.
4.3.5.6. Cover Open Sensing
The cover open sensor is located on the power supply board. It is operated by a molded tab on the front cover. When
the front cover is open the +24 V and +5 V supplies to the DC fan, solenoid, main motor, polygon motor in the laser
unit, HVPS and laser diode are cut off.
4.3.5.7. DC Fan/Solenoid Driving Circuit
A fan driving circuit is controlled by the CPU via a transistor. It is automatically turned off when the printer enters
sleep mode. There are two solenoids, these are driven by signals from the CPU (
tray paper pick ).
4.3.5.8. Motor Driving Circuit
The main motor drives the paper feed, developing unit, fuser, and exit assembly. The circuit is driven by software
which controls the acceleration, constant speed, and deceleration profiles. The Motor is driven using an A3977 driver
IC.