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Troubleshooting
This test allows you to adjust the Y-Axis Scaling.
The scaling (dpi) in the mechanical scan direction (Y-Axis) depends on the
speed of the stepper motor relative to the scanline Exposure Time. The
default motor speed can be changed ± 1%, either from Test 12 or by using
the 'Scanner Setup/Correction factor ...' option of SW copying. The
correction factor is stored in the Flash Memory on the Driver Board.
Test 13: Switch Scanner to Test Mode
This test allows you to switch the scanner back to Test Mode. Useful if the
scanner gets out of Test Mode, e.g. if it has to be turned OFF/ON during
troubleshooting.
Test 20: Noise Test
The purpose of this test is to detect and locate the possible cause (dust, dirt,
scratches,..) of vertical lines running from top to bottom of the scanned
image.
When the test is executed, it scans the White Calibration Area of the
Calibration Sheet and displays, for each color channel, the graytone values
of each separate pixel averaged over the scanned band.
The displayed image of the Calibration Sheet will be superimposed by low
level noise caused by the CCD chip, and larger spikes most likely caused by
dust, dirt, scratches, or similar defects on the Glass Plate. In rare cases,
larger spikes may be caused by dust, dirt, or pixel faults on the CCD chip.
The positions of larger spikes are shown by the numbers (cm or inch units)
opposite to the spikes. The numbers refer to the Sideload-ruler on the
scanner. Larger spikes going downwards are often caused by dust, dirt,
scratches, or similar defects on the Glass Plate and may be removed by
cleaning the Glass Plate. Downward spikes often show up as darker vertical
lines in the scanned image.
Larger spikes going upwards are often caused by dust or dirt present on the
Glass Plate during the last calibration with Scanner Maintenance. These
defects are memorized by the Light Profiles stored in the Flash Memory and
can only be removed by cleaning of the Glass Plate followed by running
Scanner Maintenance again. Upward spikes show up as very bright vertical
lines in the scanned image.
White vertical lines in the scanned image may be found even if Noise Test
shows a perfectly 'clean' scanner. In this case, the cause may be white dust
or particles on the backside of the Glass Plate having the same color as the
white background. In this case, the Light Profiles of SCANtest 6, Test 9 may
show upwards going spikes when a dark original is placed in the scan-area.
Test 21: SCANdump
SCANdump is a tool for remote diagnostic. SCANdump saves the light
profile from the cameras, error codes, and statistics.
When the test is executed, the file SCANdump.con will be placed in the
HP Designjet T1100 MFP, 4500mfp, 4500 Scanner, 820 MFP Service Manual
1-7

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Troubleshooting

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