HP LaserJet Pro 400 Service Manual - Page 106

DC controller PCA WARNING! Do not install a replacement formatter PCA and a replacement DC controller PCA at the same time. The formatter PCA and the DC controller PCA store important product configuration information (NVRAM data) that is lost if both PCAs are replaced at the same time. When the product power is turned on, the formatter restores the NVRAM data to a replacement DC controller. Replacing both the DC controller and the formatter at the same time will result in severe print-quality problems. Replacing the DC controller PCA before the formatter PCA Use the following procedure if you need to install a replacement DC controller and a replacement formatter PCA. 1. Install a replacement DC controller PCA. 2. Turn the product on, and wait for the print-cartridge volume indicators to appear on the controlpanel display. NOTE: This allows important product information to be written to the replacement DC controller PCA. 3. Turn the product off. 4. Install a replacement formatter PCA. See Formatter PCA and fax PCA on page 76. 5. Turn the product on. Before you proceed, remove the following components: ● Right cover. See Right cover on page 23. ● Scanner assembly. See Scanner assembly on page 26. ● Upper cover. See Upper-cover assembly on page 51. 80 Chapter 1 Removal and replacement ENWW