MFC-9840CDW FAQs & Troubleshooting MFC-9840CDW Not your product? Sort by: Updated Date Popularity 4 Results 1. 29/01/2014 How do I clean the drum unit? 2. 27/02/2009 How do I clean the laser scanner windows? 3. 27/02/2009 How do I clean the scanner to improve the copy or fax quality? 4. 27/02/2009 How do I clean the corona wires? Cleaning FAQs & Troubleshooting