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Color LaserJets: Don't Sweat the Small Stuff

19 Mar, 2004 By: Steve Geishirt imageSource

Color LaserJets: Don't Sweat the Small Stuff

Sometimes the bigger problems aren’t the ones that drive you crazy—it’s the
little things that get to you. After working on the newer HP Color LaserJet 4600
and 5500 printers, we fixed on two relatively small issues that are causing big
headaches for techs. Although small, these problems can lead techs scratching
their heads in confusion and spending way too much time trying to figure out a

Don’t Raise the White Flag

The first issue has to deal with the flag on the outside of the CLJ4600 fuser.
If you’ve changed out the fuser in a CLJ4600 printer before, you’ve likely found
this flag. You may have witnessed, as I have, a technician pulling a fuser from
a CLJ4600 printer with following scenario:

one hand, the technician picks up the fuser by the center of the unit and begins
to pull it out of the printer. As they are picking it up, they find the fuser is
a lot heavier than they first anticipated and it begins to slip from this one
handed grip. This slipping is intensified if the fuser is hot, and increases
proportional to the temperature of the unit. As the fuser slides out of the
technician’s hand, the tech reaches out with the other hand to keep from
dropping the fuser unit. Before the second hand is able to help out, the first
hand, desperately grasping the fuser, comes across this flag we were talking
about earlier. The technician’s fingers catch the flag which begins to slow the
slipping. A glimmer of hope reaches the distressed tech, who has already
pictured the fuser in 4600 tiny pieces on the floor. This hope is short-lived
when the tech hears a little “snap” and one of the pins holding the flag in
place breaks off. The flag and its supporting pins were not engineered to
support the weight of the fuser has snapped under the pressure. Yes, the fuser
has been saved but at what cost. The damage is done.

this may seem a bit far fetched, this is not an uncommon scene. In fact, our
tech support professionals tell us they usually get a couple of calls a week on
this issue. With the flag broken off, the printer will power up and print but
with no flag to sweep into the photo sensor, the printer comes up with a
13.0A.00 error. This tells us that the bin full sensor is also used to detect
paper jam conditions in the fuser. Placing tape in the photo sensor causes the
printer to automatically come up with a “standard output bin full” message and
not print. One way or another, the fuser must be repaired, or replaced, for the
printer to work again.

repair of the fuser is not too bad. Normally the flag itself is just fine, but
one of the covers is broken. The pins that hold the flag in place are molded
into the left and right side covers. One pin breaks, and the flag won’t stay in
place. You simply need to know which pin, or should we say cover, is broken and
replace it—it could be either. For your reference, the left cover is part number
RF5-3774-030 and the right cover is part number RF5-3775-030. Note the last
three digits of “030” which denotes an upgrade has taken place. This is a recent
change, which is why this issue is all the more important.

Remember what I said earlier about the little stuff getting to you? The covers
and flag have been re-engineered to better deal with the stresses of being
removed. The covers now have larger pins so they don’t break as easily. These
new covers are available on the market. However, at the time this article is
being written, the flags, which have also been re-engineered to accommodate the
larger pins, are not yet available. This has created a mismatch situation for
some customers who ordered the new covers but still had the old flag—the two
don’t work together. Not to fret! By the time this article is printed, the new
flags will be available with their new upgraded part number RB2-8498-020. Once
again, the “020” refers to an upgraded part. The “020” version will have the
larger holes to accommodate the larger pins in the covers. Also, don’t forget,
you will need to order one of each part so they all work together:

1 -
RF5-3774-030 Left Cover

1 - RF5-3775-030 Right Cover

1 - RB2-8498-020 Flag

Alignment Issues

This second problem is becoming a more common scenario and often causes image
problems on the CLJ5500 rather than the CLJ4600. The problem relates to the ETB
(Electrostatic Transfer/Transport Belt) and its relation to the density sensors.
When a printer is first powered up, it calibrates the colors to keep them in
spec. In doing this, color squares or swatches are written onto the ETB in full
and half density. These swatches are rotated up to the top of the belt, the
density sensors just under the display. The density sensors check the density of
the swatches and make high voltage power supply adjustments to keep the
densities within their specified range.

key part of checking the density is the alignment of the belt to the sensors.
Too close or too far and the readings will be incorrect. To keep things
consistent with a belt that opens and closes on a hinge, there are two aligner
arms, or tabs, at the top of each ETB. The tab on the right is black while the
one of the left is white. When the ETB is in the closed position, these two tabs
guide the density sensors into proximity with the belt for consistent alignment.

appears to be happening is that one or both of the tabs will break, allowing
them to rotate instead of staying in the up position. When they rotate, they
will incorrectly point toward the printer (see Figure 1 and Figure 2). When this
occurs on the CLJ4600, the ETB will not shut fully because the tabs are pushing
it out. The end user will not be able to get the top door closed which typically
means a service call. While broken tabs will be noticeable to the educated eye,
an end user will not likely pick up on this as they hadn’t noticed previously if
the tabs should rotate or not. While this is a relatively small challenge that
can be fixed by replacing the ETB on the CLJ4600, it’s a more difficult problem
on the CLJ5500.

tabs break on this printer too, but if only the left tab (white) flips down as
the door closes, the rest of the covers will close too. And, when the printer
does calibrate, the left side of the belt is farther away from the right side.
The obvious results are messed up colors. Besides that, there is an ever bigger
problem. Since the ETB is bent, or warped, in the printer, when the belt rotates
it moves to one side of belt unit. The belt shows its unhappiness by grinding up
against the edge of the ETB, damaging the belt. It actually sounds more like
paper crinkling (see Figure 3).

Customers complaining of a crinkling noise when the printer runs and color
problems (this may not be a complaint because it depends upon their level of
color pickiness) can be given a short term fix right over the phone. Have the
end user open the top and bottom doors and, grabbing the green handles top left
and right of the belt unit, pull open the ETB. The white tab on the left is
usually the culprit as the right tab tends to keep the covers from completely
shutting. The white tab should be pointing straight out the top of the ETB. If
it is pointing toward the printer at a 90 degree angle, the end user should be
instructed to straighten it out (pointing straight out the top of the ETB) and
carefully close the ETB door. The top of the ETB should look flush with the top
of the printer if properly installed and the customer can begin printing again
(see Figure 4 and Figure 5).

biggest concern here is how bad the belt is damaged from the machine running
wrong. The belt can become damaged enough that it will not image the print
properly on that edge of the page. If your customer is running letter sized
paper, the bottom of the page will have print problems. The ETB will likely have
to be replaced regardless, as the end user will likely forget about the tabs and
cause more damage to the belt again.

the CLJ5500, you can see how this color issue and damage to the belt could get
you on a hunt that could take you a lot more time to troubleshoot. Now that you
know a couple more quick checks/fixes, keep them handy for the day you have a
CLJ4600 fuser to replace or cover closing issue on one of these printers.

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