HP LaserJet 4250 Service Manual - Page 322

Table 7-2 Power-on defect or blank display (continued) Problem Action 3 Replace the power-supply assembly. See Power supply. 4 Replace the dc controller. See Dc controller PCA. Note: The fan only operates during the initial startup and while printing, and when the temperature inside the printer is too high. If the temperature is too high, the fan turns on to cool the inside of the printer. The fan works, but the control-panel display is blank. 1 Print an engine test. Engine-test page. 2 If the engine test is successful, perform the following steps, in order. ● Reseat the control panel and formatter connector. See Control-panel assembly and Formatter assembly . ● Replace the control-panel cable. See Control-panel assembly. ● Replace the control-panel assembly. See Control-panel assembly. ● (HP Laserjet 4200 and 4300 Series printers only) Replace the firmware DIMM. See Firmware DIMM (LJ 4200/4300 only). ● Replace the formatter. See Formatter assembly . 3 If the engine test is not successful, remove the formatter and attempt to perform the engine test again. If the engine test is successful with the formatter removed, replace the formatter. See Formatter assembly . If the test is not successful with the formatter removed, replace the dc controller PCA. See Dc controller PCA. 308 7 Troubleshooting