MFC-9420CN FAQs & Troubleshooting MFC-9420CN Not your product? Sort by: Updated Date Popularity 3 Results 1. 01/27/2014 How do I install the Optional Lower Tray Unit? 2. 01/27/2014 How do I install additional memory? 3. 11/08/2005 What kind of memory can I use? Consumables / Paper / Accessories FAQs & Troubleshooting