Apple Self Repair Guides

Photosensitive Drum Life Detection

Outline The printer determines the life of the photosensitive drum mathemati cally by tracking page count. When a new photoconductor cartridge is installed, the EEPROM on the DC controller board logs the current page count of the printer. This value becomes the starting page count for that photoconductor. During each subsequent print, the controller compares the running page count against the starting page count stored in EEPROM. If the difference between the two values reaches a prescribed number, the controller determines that end of life has occurred and instructs the I/O controller to report the appropriate alert to the status panel.

Only new cartridges initialize page count. Otherwise, the printer would recognize as new any used cartridge that had been removed and reinstalled. This safeguard is achieved by storing a second value in EEPROM, the thickness of the photosensitive drum.

Note: Before replacing the DC controller board, you must download these values (see Chapter 2). If you are installing a new photocon-ductor and there is a chance that the old one will be reinstalled, as a troubleshooting measure for example, you must also download these values.

Drum The thickness of the photosensitive drum is detected upon power-on,

Thickness door-open, and each time a certain number of prints is reached. Drum

Detection thickness is detected by measuring the discharged current value after charging by the primary charging roller to the photosensitive drum. For correct measurement of the current value, the photosensitive drum and the transfer drum are separated from each other and the thickness detection is performed. See "Drum Separation" below.

The photosensitive drum thickness detection circuit is in the highvoltage power supply board. After the power is turned on and the main motor is turned on, the drum press solenoid (SL7) is turned on and the photosensitive drum and the transfer drum are separated. Then the drum motor is turned on, the primary charging DC voltage drive signal (/HV1DC1) and the primary charging AC voltage drive signal (/HV1AC1) are set to "L," the primary charging AC voltage select signal (/HV1AC0) is set to "L," and the primary charging DC voltage select signal (/HV1DC0) is set to "H" to apply the primary charging voltage to the photosensitive drum.

After charging for a specified period of time, the /HV1DC1 signal is set to "H," the application of the primary DC voltage is stopped, and the discharging current value is measured by the photosensitive drum thickness detection circuit on the high-voltage power supply board. The measured current value is sent from the high-voltage control IC to the mechanical controller as the drum thickness sense signals (SENSE0 and SENSE1). The mechanical controller converts these signals into the corresponding time data and sends them to the DC controller. Based on these signals, the CPU on the DC controller determines whether the photoconductor cartridge has been replaced with a new one and whether the photoconductor is installed in the printer.

Primary Charging Roller

Photosensitive Drum

High-Voltage Power Supply Photosensitive Drum Thickness Detection Circuit

Primary Charging Roller

Photosensitive Drum

Primary Charging Roller Voltage Generation Circuit

Current Detection Circuit/ Current/Voltage Conversion Circuit

Amplification Circuit

Filter

Amplification Circuit

Voltage/Pulse Width Conversion Circuit

Primary Charging Roller Voltage Generation Circuit

	IC1003
/HV1DC0
/HV1DC1	HighVoltage Control IC
/HV1AC0
/HV1AC1
SENSE1 SENSE0 SENSE1 Drum The photosensitive drum and the transfer drum are separated when the Separation photosensitive drum thickness detection is performed, the overhead- transparency mode is activated, or the photoconductor cartridge is being replaced. When the mechanical controller sets the drum press signal (/DDSLON) to "L," the drum press solenoid (SL7) is turned on and drum separation cam 1 activates to move the transfer drum away from the photosensitive drum. When you lower the transfer drum lever, drum separation cam 2 moves the transfer drum away from the photosensitive drum in a manner identical to the solenoid-controlled operation described above.

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