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

Discussion in 'Electronic Repair' started by W. Curtiss Priest, Apr 6, 2007.

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  1. 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
     
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