IBM HL-5250DN - Manual (Page 77)

6. Routine Maintenance
69
When you replace the drum unit with a new one, you need to reset the drum counter by completing the
following steps:
a Make sure that the printer is turned on and the Drum LED is blinking. Press the front cover release button
and then open the front cover.
b
Press and hold down Go for about 4 seconds until all the LEDs light up. Once all four LEDs are lit, release
Go.
Improper Setup
Do not reset the drum counter when you only replace the toner cartridge.
c Take out the drum unit and toner cartridge assembly.