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LaserJet III Paper Jams

Discussion in 'Electronic Repair' started by Shawn D'Alimonte, Jan 6, 2005.

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  1. My old LJIII has started jamming again (13 PAPER JAM) and I am stuck
    figuring out what the problem is.

    The paper either stops right before the transfer assembly roller, or a
    bit before the fuser. If it passes the rollers a loop tends to form
    between the pickup roller and transfer roller and sometimes it starts
    feeding a second sheet. I don't see why it feeds a second sheet since
    the engine test is only one page. The paper feed mechanism seems to
    have gotten noisier as well, but I can't figure out the source of the noise.

    What I have tried so far (based on Google searches and previous repairs):
    - Checked and cleaned pickup roller and separation pad (Fairly new,
    printer not used a lot).
    - Cleaned transfer rollers (These were filthy)
    - Checked all gears for missing teeth
    - Tried another toner cartridge
    - Disassembled, cleaned and greased clutches on pickup and transfer
    roller shafts (Grease was gunked up)
    - Cleaned gummed up pads on clutch solenoids (Temporarily replaced pads
    with tape until I can find something better)
    - Checked drive motor connector
    - Cleaned gears attached to motor (Grease was gunked up)

    Have I missed anything obvious or is it time for a new(er) printer?
  2. Here, too:

    And, you have searched Google Groups for this, haven't you?

  3. Thanks for the hint.
    I did. That is where I got the idea to check the clutches and try a
    different cartridge.
  4. Neil Preston

    Neil Preston Guest

  5. I have looked at that site since they do have good FAQs as well as
    repair kits.

    I did some more debugging and found that the motor sometimes has trouble
    turning even when removed from the gears. You can feel it vibrate but
    the shaft doesn't turn much.

    When turned by hand the shaft turns smoothly. The coils measure okay
    with an ohmmeter (~4ohm to centre tap, no short between coils, all coils
    have same resistance). I also hooked the motor up to my scope and got a
    slightly distorted sine wave from each coil when I spun the shaft. All
    four coils had the same shape and voltage (using centre taps as ground).
    I think the motor itself is good.

    I tried putting a scope on the motor terminals and one of them does look
    different. Maybe the driver IC is bad, which probably means a new DC
    power supply. I need to do a little more debugging on this or start
    shopping for another printer.
  6. rb

    rb Guest

  7. Pcaorwb

    Pcaorwb Guest

    Just have to say, the LaserJetIII are real work horses, just like their
    predecessors, the IIs. Great for text and simple black&white images. I bought
    my first one from Computer Shopper back in 1990 four about $1,100. Picked up
    another one just a few months ago for $25.00.

    Tucson, AZ
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