Ac And Dc Power Service Check - Lexmark C78x Service Manual

5061

AC and DC power service check

Before proceeding with this service check remove or disconnect any options that may be installed. Turn the
machine on. If it operates correctly, reattach one option at a time until the failing option is located.
Note: Set the voltage range switch to the proper power setting for the geographic area you are in.
Note: Before proceeding with this service check, turn the printer on, and check to see if the Power on LED on
the system board is turned on.
Step Actions and questions
1 Is the LED turned on?
AC power service check
The printer appears to be inoperative when turned on with the Power on/Status LED off, the LCD
display is blank, the fuser lamps do not come on, and no motors turn.
Step Actions and questions
1 Main AC power—Make sure the printer is receiving
main AC power.
Is the printer receiving AC power?
2 AC power check (wall outlet)—Check the AC line
voltage at the AC outlet.
Is the AC line voltage correct?
3 AC power cord
Is the power cord in good condition and correctly
installed?
4 AC power check (AC line cord)—Check the AC line
voltage at the end of the AC line cord.
Is the AC line voltage correct?
5 Low voltage power supply—Turn the power off, and
disconnect the LVPS at J18 on the system board.
Measure the voltages on J18-3 and J18-4. The voltage
should measure approximately +5 V dc.
Is there approximately +5 V dc on any of these
connector pins?
2-76
Service Manual
Yes No
Go to "AC power Go to
service check" service check"
on page 2-76. on page
Yes No
Go to step 2 Inform the
customer that AC
power to the
printer is
incorrect.
Go to step 3 Inform the
customer that the
AC line voltage is
incorrect.
Go to step 4 If the cord is in
poor condition,
replace the cord.
Go to step 5 Replace the line
cord.
Replace the Replace the
system board. LVPS assembly.
See "System See
board removal" assembly
on page 4-90. removal" on
page
"DC power
2-77.
"LVPS
4-53.