Lexmark W820 Service Manual page 109

Step Actions and Questions
2 +5VDC CHECK
Measure the voltage between J400-1 and FG and J400-2 and
FG on the MCU PWB.
Is there +5VDC between J400-1 and FG?
Is there +5VDC between J400-2 and FG?
3 MCU PWB REPLACEMENT
Replace the "Engine Board (MCU PWB)" on page 4-92
Does the error code appear?
4 ESS PWB REPLACEMENT
Replace the "Controller Board (ESS PWB)" on page 4-94
Does the error code appear?
5 The following printer FRUs and areas are associated with this
specific problem. One or more of these FRUs or areas may
have failed partially or completely. If you cannot isolate this
problem using the steps in this Service Check, replace each
FRU or troubleshoot each area listed below, one at a time, until
you isolate and solve the problem.
•
Wiring and connectors linking the FRUs
•
I\O PWB
Error Code 904
There is an unnamed problem with non-volatile memory.
Logic Control on the MCU PWB had a problem with NVRAM.
Step Actions and Questions
1 RESET
1. Switch off printer main power.
2. Wait one minute.
3. Switch on printer main power.
Does the 904 error code appear?
4025-XXX
Yes No
Go to step 3 Go to the
"Printer
Wiring
Diagrams"
on page 5-14
to
troubleshoot a
loss of +5VDC
Go to step 4 Problem
solved
Go to step 5 Problem
solved
Yes No
Go to step 2 Suspect an
intermittent
problem with
the MCU
PWB, the
LVPS, or the
connectors
and wiring
linking these
FRUs.
Diagnostic Information
2-13