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FC-22 TROUBLESHOOTING 4 - 60 January 2000 © TOSHIBA TEC
(4) Background Fogging
Note:
If the main charger and developer bias outputs seem to be abnormal, replace the main high-voltage transformer of the color likely
to be abnormal with another transformer of another color likely to be normal, and then, output the chart again.
If the same color remains abnormal, check if there is any disconnection of harness between the LGC board and the main high-
voltage transformer, disconnection of high-voltage harness, the power supply defect, or stain on the main charger wire.
If the color changes as the result of replacing the main high-voltage transformer, this fogging trouble is caused by the main high-
voltage transformer defect. Therefore, replace the main high-voltage transformer of the abnormal color with new one.
After this checking, return the other main high-voltage transformer back to the original color position.
Cause/Defect area
Step
Check items Measures Remarks
Density reproduction 1 Image density reproduction defect Perform automatic adjustment of Go to step 5
gamma correction. If defects
occur.
Printer 2 Check printer image. Output test print image (04-231) for
each color and check it.
Parameter adjustment 3 Check image processing parameters. Check the value of offset amount of
value processing background.
4 Adjust image processing While checking the above encircled
parameters.
image, remove background fog by
adjusting offset amount of processing
background.
Scanner stain 5 Is the original glass or mirrors Clean them.
or lens filter dirty?
Auto-toner 6 Is the auto-toner sensor normal? Check operation of auto-toner sensor
and re-adjust.
7
Is the toner supply operating constantly?
Inspect motor and circuits.
Main charger output 8 Is the main charger output normal? Check circuits. (Note)
Developer bias 9 Is the developer bias proper? Check circuits. (Note)
Developer unit 10 Is the contact between the drum Adjust doctor-to-sleeve gap and pole
and developer material right? position.
Developer material 11 Is the developer's life finished? Replace developer material.
Drum cleaning blade 12 Is it cleaned properly? Inspect drum cleaning blade pressure.
Toner dusting 13 Is toner accumulated on the seals of Remove toner and clean.
the developer unit?