Oki MC853 User Manual page 618

Note
If the toner cartridge is not securely attached, printing quality may deteriorate.
13.
Wipe the lens of the LED head with a soft tissue paper lightly.
Note
Do not use solvents, such as methyl alcohol or thinners. They damage the LED head.
14.
Close the Output Tray (3) by pushing the both sides of the Output
Tray (3) firmly.
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