HP M4345 4345 Display Hangs in boot sequence memory count or HP logo 6/6
Robert Bohacek
A hung display is one that is stuck with the screen
displaying “initializing,” “warming up,” “calibrating,” or sometimes
nothing but a row of asterisks or blocks. Essentially,
the printer has failed to initialize. Th is article will off er an
effi cient way of tackling a particularly challenging case: the
LJ 4345 MFP. First, we will describe the procedure for most
other HP Laserjets.
General Hung Display Troubleshooting
For most Laserjets, failure to initialize can be traced
to a bad formatter or something plugged into this board
(fi rmware, memory, network card, hard disk drive, etc.). Th e
normal troubleshooting sequence is to remove everything
from the formatter that isn’t absolutely necessary for basic
operation, leaving you with a formatter
board with nothing plugged in it
except perhaps the fi rmware DIMM.
If it now comes to “Ready,” one of the
removed items is bad, and you can fi nd
out which one by re-installing them
one at a time. If the formatter/fi rmware
combination still “hangs,” then one of those two items
is defective, and the only solution is to replace them one at
a time, since the printer cannot function at all with either of
them missing.
In a few specifi c cases, hung displays can be caused by
other parts. Fuser warm-up issues can cause it in the Laser-
Jet 9000 series, as we pointed out in the Fall 2009 Service
Edge.
LJ 4345 Hung Display
After the memory count, the normal initialization
display is a small HP logo that grows and shrinks in size for
about three minutes before displaying “Ready." If it continues
cycling for much more than three minutes, the printer probably
has an initialization problem.
Th ere are two main types of problems that cause hung
displays on the 4345. On the one hand, it could be the formatter
or something plugged into the formatter. On the
other hand, it could be caused by the engine power supply or
the FN101 fan. Th e following troubleshooting sequence will
help you discover which part is causing the problem.
Ideally, you would have all parts available that are listed
at the end of the article. If not, the procedures described in
this article will probably require two service calls:
1. Troubleshooting, to determine which parts are needed.
2. Repair (installing the parts). If the printer is at a remote
site, much of the troubleshooting can be done over the phone
with the customer. Alternatively, you may want to treat this
as a depot repair, where the printer is brought to your shop.
I. Is it the Formatter/Formatter Plug-ins or the Power
Supply/Fan?
A. Observe the “heartbeat LED” (visible just below
the parallel port, or on the M4345, below the USB
port – see figure 1). In a working printer, this LED
will flash briefly on power-up, turn off during the
memory count, and then pulse on and off in a
regular pattern while the HP logo is cycling. If this
LED is not pulsing while the logo is cycling, the
problem is formatter-related. If the LED is pulsing,
it’s hard to be sure, so we need to run an engine test.
Go to step B.
B. Running an engine test on the 4345 mfp
Remove the formatter ( 1. with all its accessories
and plug-ins), and power up without it.
2. Let it warm up a few minutes.
3. Make sure there is paper in all cassettes.
4. Press the engine test button.
a. Th e engine test button is accessible through
a small single hole on the back of the printer
(see fi gure 2). Use a long, thin, non-metallic
object to reach through and press the
switch.
b. Th is may require several attempts, as you
may miss the switch if you don’t go straight
in.
5. If the printer prints an engine test sheet (a
page containing just lines), then the fan and
power supply are working. Th e problem is with
something that plugs into the formatter or the
formatter itself. Go to II.
C. If the printer does not print an engine test sheet,
either the fan or the power supply is defective. If
you have a voltmeter, you should be able to tell
which part is bad by observing fan rotation and/
or measuring the voltage going to the fan. This will
require some disassembly. You will find instructions
on page six.
II. Is it the formatter or one of the plug-ins?
A. Hard Drive.
1. Turn the printer off
2. Unplug and remove the cable that connects the
hard drive to the formatter.
3. Turn the printer back on.
4. In a normally working printer, you may get a
message that tells you that copy & send functions
are disabled, and/or that the internal disk
was not found, but you will still be able to print
from the menus or from the computer. If it still
hangs or will not print, go to 2B. If it prints,
there is a problem with the hard drive. You can
sometimes cure this by initializing the hard
drive.
a. Hard drive initialization
1. With the hard drive installed and connected,
turn the printer on and watch
the display.
2. When the memory count begins, press
and hold the right side of the “Start”
button until all three LEDs are lit,
then release it.
3. Press and release the “5” key. “INITIALIZE
DISK” should appear on
the display.
4. Press and release the “6” key. A row of
asterisks should appear on the display.
Wait for the printer to complete the
initialization sequence.
b. If initialization of the hard drive does not
work, replace it.
B. Other plug-ins.
1. Remove the formatter from the printer.
2. Reseat the compact fl ash fi rmware and base
memory. Th ese are the only two plug-ins that
the formatter requires to function.
3. Remove all other accessories (fax card, extra
DIMMs, etc.).
4. Reseat the “daughter card” that connects the
formatter to the copy processor.
5. Th en re-install the formatter and power up. If
the machine now works normally, one of the
removed items is bad. Re-install them one at
a time (cycling power each time) to fi nd out
which one. If you still have a hung display with
all those items removed, one of the remaining
items (formatter, fi rmware, base memory) is
bad, and all you can do is replace them one at a
time. But before doing that, there are two more
resets you can try.
a. Cold reset
1. Turn the printer on and watch the
display.
2. When the memory count begins, press
and hold the “6” key until all three
LEDs are lit, then release it. Th e display
should show “Select Language.”
3. Use either the “3” key (up arrow) or the
“9” key (down arrow) to scroll the display
until “Cold Reset” is highlighted.
4. Press and release the “6” key to select
the cold reset, and wait for the printer
to complete the initialization sequence.
b. NVRAM Initialization reset
1. Turn the printer on and watch the
display.
2. When the memory count begins (on
the M4345, before the memory count
begins), press and hold the “9” key until
all three LEDs fl ash once and then stay
on (this may take up to 20 seconds),
then release it.
3. Press and release the “3” key, and then
the “Start” key.
4. Press and release the “3” key as many
times as needed, until “NVRAM
INIT” appears on the display.
5. Press and release the “6” key to select
this, and wait for the printer to complete
the initialization sequence.
6. If neither reset solves the problem, replace the
fi rmware DIMM, then the base memory, then
the formatter (if necessary).
NOTE: Almost everything in this article applies equally to
the LaserJet 4345 and the LaserJet M4345. However, note
that the NVRAM initialization procedure is slightly diff erent
on the M4345. Also, it does not have a separate fi rmware
DIMM or base memory
Shortcut: How to Tell if the LJ 4345 Power
Supply is Bad
When troubleshooting a hanging display on a
LJ 4345, once you have ruled out the formatter, that
leaves either Fan 1 (FN101) or the Engine Power
Supply. We at Liberty have found a way to test the
power supply without swapping parts, saving time
and money.
Th is will require removing the front cover. Th is involves
manipulating hidden plastic tabs and removing screws.
Some of these tabs may break when you remove the cover.
Do not worry, this does not cause problems, as the screws
hold the cover in place perfectly well.
A. Pull the control panel away from the printer to release
the upper locking tabs. Th en rotate it away from the
printer and unplug one connector from the back.
B. op cover fl atbed fl ange with a pick or small fl at screwdriver, then remove it.
C. Remove two screws with a long Phillips screwdriver.
D. Open the top cover and remove one screw along the left side of the front side
E. Remove Tray 2 and remove two screws above the tray
F. Slide the output bin from the MFP.
G. Release the retaining tab on the left side of the front
cover. Th is one seems prone to breaking.
H. Remove two locking tabs on the right side [just in front of the bypass tray 1 (1 of 2).
J. We now quote frome the manual: "Flex the bottom
of the (front) cover away from the MFP to release the
locking tab at the mid-bottom, and then push up on the
cover to raise it slightly. Pull the front cover away from
the MFP to remove it."
Once you have gotten down to where the fan is visible,
you can observe whether or not it is turning during the
time that the HP logo is pulsing. If the fan is turning,
the power supply is the bad part. Go to O. If the fan is
not turning, further tests are required. Go to M.
M. Testing voltage.
1. Remove one screw (photo, right) and unhook the
thermistor. Move it to the side.
2. Remove two screws (large arrows in photo below)
and remove the power supply shield. (Later, if
you replace the fan, you will squeeze two tabs (small
arrows) and pull the fan out.)
3. To check the voltage, unplug the fan connector from
the board below it (do this with the printer powered
off ), and look at the connector on the board. It
should have three pins, as in the photo above.
4. Turn the printer back on and use the voltmeter
to measure across the outermost pins (see fi gure).
You should see something between 15 and 25 volts
DC while the HP logo is pulsing. If you do see this
voltage, the power supply is probably OK and the
fan is bad. If you do not see the voltage, the power
supply is bad. NOTE: Make sure that the voltmeter
is set to the proper range
(at least 25 VDC, or
better yet, set it to autoranging),
and that the voltmeter probes are touching the connector pins. Th is requires a good eye and a steady hand.
