HP 8550 Service Manual - Page 497

E004 (printer) The upper and lower fusing heaters have an open circuit. This error occurs when no ac current is found in the fusing heater at the start of temperature control. Cause Upper fusing heater/upper thermal switch (open circuit) Step 1 Lower fusing 2 heater, lower thermal switch (open circuit) Connectors 3 Power supply 4 (printer unit) Checks Y/N With the fusing assembly NO removed, is there electrical continuity between connectors J27F-3 (HTUH) and J27F-4 (HTUC) on the fusing assembly side? Is there electrical continuity NO between connectors J27F-3 (HTLH) and J26F-4 (HTLC) on the fusing assembly side? Are connector J222 on the dc NO controller PCB, connector J26 of the fusing assembly, and connector J101 of the printer unit power supply connected securely? Replace the power supply of the printer unit. Is the problem corrected? YES NO Action Check the upper fusing heater and the upper thermal switch. Replace the fuser if problems are found. Check the lower fusing heater and the lower thermal switch. Replace the fuser assembly if problem parts are found. Connect the connectors securely. End. Replace the dc controller PCB. E009 (printer) Cause Fusing assembly Connectors Step Checks Y/N 1 Does the rated voltage of the NO fusing assembly match the printer's voltage? 2 Are connector J222 on the dc NO controller PCB and connector J26 YES of the fusing assembly connected securely? Action Check the product number of the fuser assembly; if necessary, replace the fusing assembly or the printer unit power supply. Connect the connectors. Replace the dc controller PCB. EN Copy module troubleshooting 495