re problem when replacing cartridge wiper blade in Canon PC-10, etc. or CX laserprinters

Newsgroups: sci.electronics.repair

Subject: re problem when replacing cartridge wiper blade in Canon
PC-10, etc. or CX laserprinters

Applies to most Canon-based copiers and laserprinters including
PC-10, PC-15, PC-20, PC-25, Apple LaserWriter, and many HP laser printers
with the Canon CX or PC print engine

W. Curtiss Priest, Director, CITS
Center for Information, Technology & Society
466 Pleasant St., Melrose, MA 02176
Voice: 781-662-4044
http://www.cybertrails.org

Technical Repair Note #5
April 4, 2007

Laser/Copier Printers and Copiers

Reassembling the Cartridge

I. Introduction

This is the fifth in a series of technical repair notes for
these machines.

Incredibly rugged, there is little that goes wrong with these
Canon designed devices.

In an era where prices of new machines are low, and where
service costs are high -- re-use and repair has become a lost
art.

Yet, there is hardly anything as rewarding and engaging as
taking a known and loved machine and breathing life back into
it.

And, often, the time to do this is a fraction of the time it
takes to either have the item repaired or go about the process
of discarding one and purchasing another (with the attendent
relearning and "infant mortality" problems associated with
acquiring something new).

It is in this spirit that these repair notes are written.

Problem: Paper jams. Location of the jam is at the black
pin that has the plastic band resting on it, back side of
unit, 5 inches to the right of the inside green felt pad
over the fuser roller.

Fyi, repair of the plastic band appears in the news groups as:

Date: 2000/01/07
Subject: re: REPAIRING plastic paper feed strip in Canon PC10,
etc. or CX laserprinters

[Note: In subsequent manufacture of the feed strip I note
two improvements:

1. use a "pencil torch" -- this small flame is easily
brushed on the pee-wee clip where the jaw arms
overlap -- allowing even heating of top and
bottom of the clip jaws

Do observe heating only to discoloration, and
douse immediately with water. If the (yellow) plastic
shows any black, rather than a dark brown, the
loop is likely to break

2. to improve the weld, I now apply the clip
twice -- vertically near one side and then
vertically near the other side. This reduces
failure due to torsion

Strain test the final result using two pins and, say, a postal
scale -- apply 16 ounces. The spring, when in use inside the machine
applies about 8 ounces of tension

I note that the original Canon band is superior to using plastic
sheet used as report covers. The original band behaves like the
plastic used to hold a six-pack of cans together. The kind,
that if stretched, narrows and becomes clearer to light.
Unfortunately the plastic from such six-packs is too thick. We
need 4 mil

Consult the original note for more information

]

[Note: After years of cutting a hole in the top of the toner
hopper to refill I note that there is a fill plug. That
plug can be accessed by cutting a rectangular window into
the right side wall at the rear, just in front of a plastic
tab that identifies the cartridge to the machine. Place
cartridge level with the counter window facing you. Now
rotate the cartridge 1/4 turn, clockwise. To the far
right are two indents, a tab is typically in the lower
indent. Now, 1/8" in from the indent cut a rectangle with
a Dremel cutoff wheel that starts just above the "rub"
protrusion near the bottom, 1 1/4" high and 7/8" wide.

You will see fill cap for the toner. Pop the cap and
put a barrel made out of paper, about 3/8" I.D. to guide
toner to the opening. Then use a funnel (taped paper, again,
is fine -- disposable, only flair the end wide enough for
the toner bottle.

Always remember to remove "spent toner" via 2 other cut holes.
Symptom of a full "spent toner" receptacle are random drips
of black on the print.

Continous black streaking is always a bad silicone wiper
blade. Unit must be pulled apart. I've published how to
do this as an earlier tech note.]

***

Even a twenty-five year old Canon PC copier or laserprinter never
jams. Paper pick-up remains reliable even with well over 100,000
pages.

Yes, fuser rollers are no longer used. Heat must go through the
paper, making the use of thick stock difficult as the toner
rubs off. I compensate by taking a catalytic propane heater
(used for removing paint) and waving that heater over the toner
if the stock is thick. This also applies to the use of Avery-like
self-stick address labels. Also, the feed fingers do score
the fuser roller. Toner collects on the tips and abraids the
light coating on the aluminum fuser drum. However, one can
lightly feather these thin grooves fine carbide paper and the
quality is fine. (I used to replace these rollers ... not worth
it.)

Only recently did I find one rubber part that goes gooey.
There is a tiny roller that is spring loaded against the plastic
band (above). That presses on a rubber sleeve on a shaft that
turns. To replace this rubber, take a strip of rubber that is about
..1" thick, about .4" wide and the circumference of the plastic
hub located there. Wrap the hub, mark the overlap, cut to
fit. Now take 2 pieces of 25 lb. mono filament fishing line
and tie the "wheel" into place. Put the 2 lines about 1/16"
from each side and tighten so that they just pull into the
rubber enough to be flush. As this is a feed assist roller
between the 3 main paper rollers (before the cartridge drum)
and the fuser roller, this wheel helps keep the paper taut
as it moves to the fuser. Position the knots to fall into
the gap. Also use contact cement as a secondary attachment.

I checked two other machines. The PC-10 copier has a rubber
sleeve that is still firm. An Apple LaserWriter lost that
sleeve and I never noticed. As for the PC-10, this is a
splendid copier and because it doesn't use complex optics
like the PC-25, the xerographic prints are remarkably clear
to the point that it is difficult to tell the copy from
the original! It is the back-up copier and also the one
I use for very precise reproductions.

***

With the cartridge removed, the paper would not jam. One
can easily watch the paper move, by removing the cartridge
door, two clips and one screw.

Cause: in reassembling the cartridge after replacing the
silicone wiper blade, the problem started.

If I left the drum cover off (pop two clips from a
guide wire), there was no jamming.

In disassembling the unit the plastic arm that moves that
guide wire had become unclipped from it. I noticed it
was floppy, but didn't connect to the fact that it should
have been held to that wire.

Removing the two 10 mm. torque screws on the counter cover,
that arm could be pulled away and then pressed to latch
onto the guide wire. (I don't have torque star bits with
center holes, so I always grind away the security pin in
the center of such screws with a 1/32" diameter chishel
tooth carbide cutter.)

When the cartridge is inserted and then the cover of the
machine is pressed to latch, there is a sloped plastic arm
(often brown) that presses on this lever, opening the
drum cover. Of course, the unit could be run without the
cover but, while CX toner is non-abrasive and these drums
"last forever" -- a single scratch of the drum will make it
inferior.

The Canon PC-25 is such a wonder. Elsewhere I have a technical
note covering the only serious repair needed -- grease, deep
inside the mechanism to change the lense position for reductions
and enlargements, gets too stiff -- yes, it is a three hour
project to disassemble and reassemble -- but, you need only
do this once!


--


W. Curtiss Priest, Director, CITS
Center for Information, Technology & Society
466 Pleasant St., Melrose, MA 02176
781-662-4044 http://Cybertrails.org