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Color Printers Can Get Cataracts Too

10 Sep, 2003 By: Steve Geishirt

Color Printers Can Get Cataracts Too

Printers Can Get Cataracts Too By Steve Geishirt

seems printers are like most people-as they get older, more things break, become
more fragile or need to be repaired and maintained. This is particularly true
with the HP Color LaserJet 4500 & 8500 series. The printers were first
released October of 1998, which makes them about five years old. While five
years in human terms isn't all that long, in printer years there appears to be a
multiple of ten in comparison. That puts the 4500s and 8500s into their 50s, and
we are beginning to see some 50s related ailments. I liken one ailment to the
early stages of cataracts-the aches and pains of growing old and symptoms that
look like one thing and turn out to be another. Things are not as clear as they
may seem.

Clear Signals? Tech support has been getting many strange calls on both the 4500
series & 8500 series and it's amazing how similar the solutions are compared
to the symptoms. For instance, tech support recently took a call from a customer
whose 8500 was indicating that no toner cartridges were installed for all three
color toners. The customer was looking at one of two sensors that may be causing
this, PS621 or PS1901C.

PS621 detects the amount of toner in the cartridge, specifically a toner low or
toner out condition. The PS1901C actually detects the color toners to see if
they are in the printer. Notice I said color toners-not the black toner.
Remember, on the 8500 series, black is not located in the carousel but is
positioned separately above the carousel. If there is a problem with PS1901C,
and there was, the machine will not recognize any of the color toner cartridges.

interesting solution to this was not replacing the sensor board, but simply
removing the toner that had built up on the sensor. In essence, much like the
human eye that sometimes gets a film build up over it (cataracts) the sensor
PS1901C had a rather similar situation. (SEE FIGURE 1)

is not the only instance when this type of situation has occurred on these
machines. On the 4500 printers, we've seen the multiple sensors clog up with
toner, which causes false errors. Some common cloggers are PS10 & PS12 (SEE
). PS10 monitors the rotation of the carousel and position of each
color; it will give a 54.2 error should it clog up. PS12 checks to see if there
is toner in each toner cartridge as they rotate into developing position (the
4500 series has the black toner cartridge in carousel unlike the 8500 series).
If the photo sensor is clogged with toner, it will not detect a toner low, or
toner out condition or even a missing toner cartridge. So the issue is not just
the false error that can stop the machine from printing, but also false sensing
of information that can cause the printer to not produce a message when it

reported false errors due to toner building up in the photo sensors on the 4500
series have been related to PS2 registration sensor (SEE FIGURE
), which would
cause a 13.0 input jam error with paper stopping at the registration roller.
This false error can also mimic another common failure symptom of the old
"paper stuck in the connector". Paper in the connector keeps the
electronic signals from getting to and from the tray, causing the constant jam
at the registration rollers. The male and female connectors are located under
the registration roller and corresponding inside of the printer. Another common
toner collector is PS301 (overhead transparency sensor), which is located right
next to the registration sensor. Symptoms of toner build up include a 54.6 error

the 8500 series, the registration sensor-surprise-PS1 (SEE FIGURE
) also tends
to build up with toner and causes a "clear paper jam" message and a
13.00.02 error in the event log. The sensor is under the registration assembly
in the registration frame assembly and can be accessed by removing the
registration assembly (see manual for removal procedures). Right next to the
registration sensor (PS1), there are two overhead transparency sensors, also
located below the registration assembly on the registration frame assembly.
Toner clogging up the overhead transparency sensors creates the second type of
false error - not indicating a problem when there is one. The job of the
transparency sensors is to detect their presence so two important things happen:
they fuse at a lower temperature and speed to fully impregnate the toner into
the transparency, and secondly, keep the transparency from going through the
duplex unit should duplex be turned on. For those of you who are clearing out
transparencies from duplex assemblies, this should help you determine where to
look to fix this.

we are talking about false errors that are created when toner gets into the
photo sensors, there is one false error I've had several calls on related to the
photo sensors, but is not an issue of toner clogging it up. The "Toner
(color) Out" error has happened to us when trouble-shooting a machine, and
in training; "color" refers to the color the printer is looking for:
cyan, magenta, yellow or black. What happens here is when the left side panel is
removed and a fairly bright light is shining directly down on that side of the
machine, the photo sensor that detects toner low/toner out conditions, PS12 may
see the ceiling lights instead of its proper feedback, causing a false toner out
error. Sometimes the lights are bright enough that it takes a couple of minutes
to reset the sensor and the machine will continue to insist it has no toner to
print with for several minutes.

Clearly Again An important issue of discussion is how to clean out toner-clogged
sensors. Most service technicians I talk to still like to use canned air and,
while canned air does a great job of cleaning out the photo sensor, it also
tends to send a cloud of toner dust in the air. At the customer site this is
unacceptable. Back at the shop, it creates a mess and is still unacceptable. I'm
a firm believer in the use of toner vacuums which are designed to filter out
particles down to the 0.5 micron level. Toner particles for these machines are
down to five microns in size with smaller particles likely to come down the
road. To give you an idea of how small five microns is, smoke particles are
around one micron - now that's small!

a standard vacuum only circulates toner through the collection bag and back out
into the air again-use a proper toner vacuum! Even when using a toner vacuum, it
may not get all the toner out of the photo sensor. The use of a good cleaning
brush is a realistic solution and a valuable tool to have in your tool case. In
the worst case, after vacuuming out the printer, a technician may have to use
canned air to clean out the sensor. Since that air will go everywhere inside the
printer, you will either want to remove the photo sensor to blow it out or make
sure you have cleaned the machine well. If you don't, you may find yourself
apologizing to your customers for the mess.

good question I hear from service technicians is why these machines are so prone
to toner flyaway? Techs often state how dirty the machines get compared to
others they have worked on and that's after having cleaned them only a week or
so before. As most of us have learned, the toner particles in these machines are
different than other color and monochrome printers. The 4500 and 8500 series and
now the 2500, 4600 and 5500 series are using Canon's "S Toner," which
is not a ground up mono component toner (plastic resin & iron oxide bonded
together). "S Toner" is chemically manufactured and has a wax core.
The wax takes the place of the silicon oil many other color printers use in the
fusing process to mix different color toners together and keep toner from
sticking to the fuser rollers.

Toner" is a great toner technology, but its one downfall appears to be that
it's lightweight. Since there is no iron oxide forcing "S Toner" to
stick to the magnetic developing roller, this toner floats all over the printer.
The 4500, 8500 & 2500 printers utilize a carousel system to move toner into
position with the image drum, rotating them around and around. Toner tends to
flake off the cartridges and float all over, thus our clogged sensors. This is
why the toner tends to get into the photo sensors on these machines, as well as
everywhere else.

the positive side, the new single pass color technologies utilized by the 4600
& 5500 series leave a lot less of an opportunity for toner to float around
the printer. Paper moves up a transport belt and toner is placed directly onto
the paper from each image drum cartridge before being sent to the fuser. There
is much less chance of toner getting all over the inside of the printer with
this straight shot paper path and non carousel rotating toners.

will tell how effective the new inline color 4600 & 5500 printers are at
keeping toner where it belongs and out of the photo sensors. I suspect it will
do a better job, just looking at them. I've seen printers introduced become
discontinued, replaced and begin the aging process all the way back to the HP
LaserJet II series. From those years of learning, I can promise this-the new
printers will also grow old as all printers do and have their aches and pains
show. We, service techs, will grow older with them, but hopefully once these
printers are ancient technology and at the end of their life cycle, we the
service technicians won't be the ones with the cataract issues.

Geishirt has been providing laser printer training and technical training for
PARTS NOW! for over ten years. PARTS NOW! is a major printer parts wholesaler
for HP, Canon, Lexmark and Okidata. To contact PARTS NOW! call 800/886-6688 or
visit www.partsnowinc.com. Steve can be contacted at the above phone number of
send e-mails to sgeishirt@partsnowinc.com.


Figure 1: Shown is a CLJ 8500 printer with the front door open. The enlarged
area shows the location of PS1901C, which detects toner cartridges in the

Figure 2: Shown is a 4500 printer with the left panel removed. PS10
detects carousel rotation & positioning of colors. PS12 detects toner in the
toner cartridges as they rotate into position.

Figure 3: The lower drawer of a 4500 printer is pulled out with the transfer
belt removed. Red arrow points to the registration sensor PS2. The yellow arrow
points to one of the connectors that sometimes gets paper stuck in it mimicking
a sensor failure.

Figure 4: This right side view of the inside of the CLJ 8500 with the transfer
drum removed shows the registration roller with PS1 just before it. The overhead
transparencies are located to the left and right of PS1.

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