Lexmark T642 Service Manual - Page 121

4061-xx0 FRU 3 +5 V dc test point on the system board Action Check for approximately +5 V dc at the +5 V test point on the system board. Note: Use care not to short adjacent voltage test points. 4 System board 5 LVPS If the voltage is correct, replace the system board assembly. If the voltage is incorrect, go to step 4. Check to make sure the LVPS cable is correctly installed at J27 on the system board. If not, reseat and recheck the voltage at the +5 V dc test point on the system board. If test point does not measure +5 V dc, go to step 5. Unplug the AC line cord from the LVPS and disconnect the LVPS cable to the system board. Reconnect the AC line cord and measure the voltage on CN2-1 on the LVPS. The voltage should measure approximately +5 V dc. 6 Features or option installed on the interconnect card assembly 7 LVPS fuse F1 (primary power) 8 Loads connected to the system board If the voltage is correct, go to step 6. If the voltage is incorrect, replace the LVPS assembly. See "Low voltage power supply removal" on page 4-54 Warning: Observe all the ESD precautions and turn the printer off before any feature or option cards are removed or replaced. Remove one option/feature at a time to help isolate the failing part. Replace the faulty part. Unplug the AC line cord, remove the LVPS from the printer, and check the continuity of fuse F1. See "Low voltage power supply removal" on page 4-54. If continuity is correct, replace the LVPS assembly. If the voltage is incorrect, replace the LVPS assembly. Turn the printer off and disconnect each cable connected to the system board and each option installed on the system board until the problem is located. Warning: When removing any card installed on the system board observe all ESD precautions when handling these options. Diagnostic information 2-81