Lexmark Optra T Service Manual - Page 62

4069-XXX FRU 9 Engine Board Action Turn the printer off and disconnect all the cables from the engine board. Check for +5 V dc at the engine board test point. If incorrect, replace the FRUs in the following order: engine board interconnect board If correct, turn the printer off and reconnect one cable at a time until you find the defective assembly. Service Tip: A short or low resistance load that is attached to the engine board can cause the LVPS to overcurrent and shut the +5 V dc supply down to 0 V dc. Service Tip: Check the engine board for burn marks or other damage, especially R20,R21, R22 and R23 located next to the upper left engine board mounting screw. If this screw is overtightened it might deform the engine board shield and cause it to short out these resistors. 2-34 Service Manual