How to clean Samsung M4020ND Laser Printer's the transfer roller 

How to clean Samsung M4020ND Laser Printer's the transfer roller
Decline in Print Quality After Long-Term Use: Printed documents may exhibit spots, stripes. This issue is typically caused by dirt on the scanning mirror, the transfer roller, or the aging of the toner cartridge. Here is a method for cleaning the transfer roller. Items you need to prepare:
Dust-Off Compressed Gas
Acetone
Cotton swab
Tweezers
Step 1: Turn off the Printer and Unplug It
Always ensure your printer is turned off and unplugged from the power source before starting any maintenance.
Step 2: Open the back panel of the Printer
Flip the cover to access the transfer roller. Use compressed gas to remove dust.
Step 3: Carefully clean the transfer roller
Moisten a cotton swab with Acetone and gently wipe the transfer roller. Rotate the roller using the gear at the end.
Step 4: Clean the Paper Separation Fingers
Use tweezers to lift the Paper Separation Fingers and clean them with a cotton swab.
Step 5: Remove dust with compressed gas
Once again, use compressed gas to remove any remaining dust. Then, return all parts to their original positions.
Reinstall the toner cartridge and paper tray. Reconnect the power and turn on the printer.
Print a Test Page
Finally, print a test page to ensure everything is working correctly.