HP 4550 Service Manual - Page 302

Diagnostics mode CAUTION Note This section provides an overview of the diagnostic tools incorporated into the HP Color LaserJet 4500/4500N/4500DN printer and the HP Color LaserJet 4550/4550N/4550DN/4550HDN printer. Take caution when performing printer diagnostics to avoid risk of injury. Only trained service personnel should access the diagnostics mode with the skins removed. There are two diagnostic sections built into the firmware, one for the formatter and the other for the engine. Each section contains different tests that allow the service technician to verify printer functionality. While in diagnostics mode there are no error messages associated with these tests. Therefore, determination of the problem will rely on the technician's skill. To exit diagnostics mode, turn off the printer. In the 4550 series, you can abort a test run by pressing the [CANCEL JOB] key and holding it down until the display shows the menu again. In some cases, it will take several seconds. To cancel the NVRAM test while it is running, press the [CANCEL JOB] key and hold it down until the display show the menu again. NVRAM is put back in its original form, and an error is logged in the Fault log. When the Attention LED is on, then there ahs been an error in the test. Press the [MENU] key to get to the Fault log menu, the [ITEM] key to see the different log messages, and the [-VALUE+] key to scroll the message back and forth. Entering diagnostics mode 1 To open diagnostics mode, hold down the left side of the [ITEM] key and turn on the printer. Formatter diagnostics Formatter diagnostics are designed to be used by qualified service personnel to thoroughly test the functionality of the formatter. If all the tests pass, the formatter is working correctly and it can be assumed that the problem resides elsewhere. Listed below are descriptions of the formatter tests available. Table 7-27 Formatter diagnostics Test Description REPEAT If set to YES, the tests will run continuously until interrupted. In the 4550 series only, [CANCEL JOB] will abort the test. ON FAULT The following will occur for each setting: BREAK - the test will stop when a failure occurs. PAUSE - the test will stop for a short period of time then resume with the remaining tests. CONT - the tests will continue even when a failure occurs. ROM CRC 4500 series only. Tests the firmware ROM for correct functionality. DRAM Tests the on-board RAM and the DIMMs. SRAM 1 Tests the SRAM inside the ASIC. SRAM 2 Tests the SRAM physically mounted on the formatter. 300 Troubleshooting C7085-90921