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HP Officejet G85 (and others) "Scanner faliure" repair guide

Discussion in 'Electronic Repair' started by [email protected], Apr 3, 2007.

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  1. Guest

    Hi,

    Recently just fixed an HP Officejet G85 which had the dreaded "Scanner
    failure" message on the screen whenever it was asked to copy, scan or
    fax, or whenever it went onto power save. When it got the error
    message, it would sometimes still print, but often it "locked solid",
    and none of the buttons on the front even beeped like they normally
    do.

    I solved the problem, and thought I'd share a diganosis guide with you
    since a lot of other people seem to have this problem and no solution.

    In summary, common problems are:
    dirty mirrors
    dirty glass (bottom)
    failed bulb
    wonky alignment strip
    jammed head
    bad belt
    failed motor.


    Do each suggestion below, and after each test it and see if the
    problem still occurs.

    First, press the # key and the 6 key at the same time as plugging in
    the power cord and switching it on. This will do a full reset, and
    may fix the issue.

    Next have a look inside the scanner through the glass while you turn
    it on or while pressing copy. Do you see the scanner head move? If
    you don't, then there's a problem with the motor or it's jammed - see
    below. Do you see the light come (evenly across the whole length)?
    If you don't, you probably need a new scanner bulb. Do you hear any
    "grinding" noises while it's moving? If you do, see below. If you
    havn't got any of those problems, it will be worth trying the
    procedure below as well, because dirt inside can often stop it
    working.

    Next we're going to take it apart. It's quite easy to get apart as
    long as you're careful, although If you're not sure about dismantling
    things, print this page out and ask someone techy to do it... As
    always, I can't guarantee it won't be broken by you doing this, but I
    fixed mine this way, and you havn't got much to loose taking apart an
    already pretty useless thing (out of print, copy, scan and fax, only
    print works). You will need a set of torx screwdrivers.

    To take it apart, fully lift up the scanner lit and lift it off.
    There's a cable attaching it to the main scanner base you'll have to
    unclip and unplug.

    Next, remove the piece of plastic on the button pannel - you should be
    able to do that with your fingernails round the edge. It has lots of
    clip-like things, so you need to pull quite firmly to detach it.

    Next fully remove the buttons themselves. Do that by pushing back the
    clip at the bottom edge of the button panel and sliding the whole
    pannel left, then lifting it out. Remove the little wire attaching
    it, remembering which way round it fits in.

    Now you need a torx screwdriver (this is a special type of screw, so
    if you havn't got the right type of screwdriver you won't be able to
    undo it) to get the scanner glass off. Remove the two screws at the
    back of the scanner, down two deep holes on the top surface. Now
    unclip the front edge of the top surface, with the two large clips
    down where the buttons were (these are hard to unclip - use a small
    screwdriver to "lift" each clip while lifting the surface a bit). Now
    lift the entire surface off and put it somewhere it won't get
    damaged. While you're at it, clean both the top and bottom with glass
    cleaner.

    Now you're in. Check all these things:

    On the scanner glass, there is an alignment strip glued to it. Check
    this is exactly parallel with the edge of the glass. If it's at an
    angle with one edge more than about 3 mm out, the scanner won't work.
    If it's not, remove the glass from the plastic and heat the strip with
    a hairdryer and peel it off. use glass cleaner to remove the glue,
    and then put the strip back on where it was, but straight. Do not
    reglue it with new glue, because the middle of the strip is
    intentionally not sticky so the scanner can calibrate colours better
    without the glue getting in the way.

    Check that the scanner "head" isn't rubbing on anything. It should
    move from end to end freely when you rotate the wheel on the little
    motor. Watch out for it touching the white pulley at the rightmost
    end - this will cause it to misalign, and can be fixed with a tiny
    piece of folded paper under the right end of the metal bar to raise it
    slightly. If you came here because the scanner head wasn't moving at
    all, but yet it didn't seem to be rubbing on anything, it may be the
    motors failed. Check all it's connections, or otherwise you may need
    to get a new one. Alternatively, a failed motor driver in the lower
    half of the scanner could also cause that, but thats out of the scope
    of this guide.

    Make sure that the little clear plastic wheel on the motor (back left
    of the scanner) is very clean. Clean it carefully with a kitchen
    towl. If it's got printer ink on (quite likley), clean it off with a
    slightly damp kitchen cloth, but don't let anything get wet. Also
    clean the little sensors either side of the wheel. This wheel is used
    for detecting the position of the scanner, and if it's dirty it won't
    work.

    If you found anything bad and fixed it, now would be a good time to
    put it together and test it before delving deeper as to why it doesn't
    work. Otherwise carry on with taking apart the scanner "head".

    To remove the scanner head, de-tension the belt by moving the white
    leaver at the back right (on the "floor" of the scanner bed). by
    slightly lifting the leaver you can detension it a lot. Now remove
    the belt from both pulleys. If the belt has any badly worn parts (ie.
    where it is no longer toothed), then you'll need a new one, which
    should fix the problem.

    Next remove the flat white data cable from the head. Do do that,
    unclip the top cover with the clips at either end of it, and carefully
    pull the white cable out of the circuit board. Now you should be able
    to fully remove the head, complete with metal bar, to a new place to
    work on it.

    If you came here to find out how to fit a new bulb, this is the place
    to fit it. unplug the bulb from the smaller circuit board, and remove
    the whole bulb assembly by carefully rotating it to get it free of the
    black plastic housing. the bulb itself can be wiggled out of the
    aluminium, but it's very fragile. The reflector is supposed to have
    black edges - thats not a defect.

    Otherwise, you next want to take off the bottom of the "head". You'll
    need a normal cross head (maybe philips) to do that. When you're in,
    you should see a load of pieces of glass. they're mirrors, and they
    must be squeaky clean. If any aren't, then clean them carefully.
    They can easily get dirty, as the printer below puts a lot of ink dust
    into the air, which drifts into the scanner section.

    If your scanner suffers from light leakage (where copying a portrait
    black sheet would give it coloured or white vertical bands), then
    solve it by filling the gaps round (a) the mirror thats visible from
    the outside of the scanner head (the shortest one), and (b) the back
    edge of the aluminium housing for the light, with black tape.

    You can also take off the circuit board and clean the actual scanning
    sensor, but It seems fairly sealed, so I don't think it would get
    dirty.

    Next put everything back together, doing the above instructions in
    reverse, making sure every wire is firmly plugged in, and test. When
    you're testing, if you don't touch it, you can switch it on while it's
    apart. The whole scanner, with the exception of the flourescant
    light, is a safe low voltage. Note that the light and motor should
    work with everything apart, but it will still come up with the scanner
    error since it can't find it's alignment mark on the scanner glass.
    To fully test you need to reassemble at least the scanner glass, and
    it should then copy. You don't need to put the hinged lid back on.
    You do need the buttons plugged in for all tests so you can switch it
    on.



    If the above guide helped you, reply or email me so I know peple
    actually read and use these guides I make, to encourage me to write
    more.
     
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