HP DesignJet T730 User guide - Page 154
Random vertical lines, Wrinkles or folds, The problem of vertical streaks cannot always be solved
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Scanner cleanliness is paramount to ensure good image quality. Before proceeding with any troubleshooting, make sure the glass scanbars are clean and in good condition and the pressure sliders (wide, white plastic parts) are also in good and clean condition. See Clean the scanner scanbars on page 109. Some of the corrective actions proposed here require the use of the Scanner Diagnostic Plot, which you can print and scan as indicated in The scanner diagnostic plot on page 165. When copying, to be sure that the defect does not come from the printing function, use this diagnostic plot to detect any scanning issue. Do not use any printed version of this guide to test the scanner, as the resolution of the images included here is insufficient. Use the diagnostic plot when recommended in response to any of the errors described in this chapter. Random vertical lines This is one of the most common issues in sheet-fed scanners. Usually, the vertical streaks are caused by dust particles inside the scanner, or miscalibration of the scanner (in these cases, the problem can be solved). Here are some examples of images suffering from vertical lines or streaks. NOTE: The black arrow indicates the scanning direction. Actions 1. Clean the scanner's glass scanbars and the original to be scanned as described in Clean the scanner scanbars on page 109. Restart the printer and re-scan your original afterwards. 2. If the streaks remain, recalibrate the scanner as indicated in Calibrate the scanner on page 111. Restart the scanner and re-scan your original after the calibration is completed. 3. If the streaks still remain, check the scanner's glass scanbars and sliders visually. If they are damaged (scratched or broken), call HP support. NOTE: The problem of vertical streaks cannot always be solved, due to the technological limitations of CIS technology. If the streaks remain after the corrective actions explained above, then no further action can be taken to improve the image quality, except to buy a more expensive CCD scanner. HP offers HD Scanners with CCD technology for customers with higher quality requirements. Wrinkles or folds Scanners based on CIS technology have a high optical resolution within their focus plane, at the price of a very limited depth of field. Hence, the images are sharp and detailed when the scanned original is perfectly flat against the glass plate. However, whenever the original contains wrinkles or folds, these defects are clearly visible in the scanned image (as shown in the following example). 150 Chapter 17 Troubleshooting copy and scan quality issues ENWW