HP Officejet Pro 7740 ADF Scanning Issues: Why You See Vertical Lines on Every Other Page and How to Fix It

Customer Question 

My HP Officejet Pro 7740 All-in-One Printer scans perfectly when using the flatbed. Still, when scanning multiple pages through the Automatic Document Feeder (ADF), every other page comes out with vertical lines. Copying, printing, and single-page flatbed scans are fine. What could be causing this? Is this a hardware or software issue?

Answer

What Causes Vertical Lines When Scanning Through the ADF?

Based on your description and the scan samples you provided, this is a classic case of ADF-specific scanning failure. The issue does not affect the flatbed or printing functions, which suggests the malfunction is isolated to the ADF scan path. Let’s break it down:

Likely Diagnosis: CIS Sensor or Calibration Failure in the ADF

• The presence of colored vertical bands (especially when scanning multiple pages) strongly suggests a CIS (Contact Image Sensor) issue within the ADF unit.

• A dirty or obstructed scan strip can trigger vertical lines during ADF scanning, but the multicolored nature and recurrence every other page point to something more profound, likely signal interference or degradation at the hardware level.

Troubleshooting Steps You Can Try

Before considering hardware replacement, here are a few steps to isolate or potentially resolve the issue:

1. Clean the ADF Scan Strip

• Open the ADF lid and locate the narrow glass strip next to the flatbed.

• Use a lint-free cloth and isopropyl alcohol to clean this strip gently. A single speck of debris, ink, or adhesive can cause streaks or lines.

• Ensure it is scorched before testing again.

2. Test with a Single Page Through the ADF

• Run a single-page scan through the ADF. If that page comes out clean but problems arise during multi-page scans, the issue might relate to timing disruptions or vibration sensitivity during feed transitions.

3. Inspect the ADF Ribbon Cable (if comfortable doing so)

• Open the top cover of the scanner (this may require some disassembly).

• Locate and examine the flat ribbon cable connecting the ADF to the main logic board.

• A loose, pinched, or oxidized connection can cause corrupted scan data and introduce patterns or colored artifacts.

Is It Hardware or Software?

Given the consistent symptoms, we can confidently say this is not a software issue. Driver updates or firmware refreshes won’t fix this kind of hardware malfunction. Your flatbed scans and printing remain unaffected because they use a completely separate imaging sensor and processing path.

The most probable culprits are:

• A failing CIS sensor in the ADF scan module.

• A damaged or degraded ribbon cable that transmits image data from the sensor to the mainboard.

This problem is especially likely to show up intermittently at first and then become persistent, which aligns with your "every other page" observation.

Recommended Actions

• If your printer is still under HP warranty, contact their support to request a replacement ADF assembly or potentially a full-unit replacement.

• If out of warranty, it might be possible to replace the ADF's CIS module, but this depends on your comfort level with printer disassembly. Unfortunately, these parts can be challenging to find and may not be cost-effective to replace.

• For now, continue scanning using the flatbed, which remains functional and unaffected by this issue.

If you decide to dig into a DIY repair, let us know. We can help you source a replacement CIS module or walk you through the disassembly steps for checking internal connections.

Final Note

Printer hardware issues like this can be challenging to troubleshoot remotely because they require hands-on inspection. That's why we’re not able to provide remote support or repairs. However, we do offer in-person diagnostics and printer servicing through our local repair facility (https://bchtechnologies.com/printer-repair-service). Please note that service slots fill quickly, and we operate on a first-come, first-served basis, so that drop-offs may involve some wait time. While our rates may not be the lowest, we focus on quality and transparency. If a visit isn’t feasible, we recommend exploring self-repair options through online research. A great place to start is our YouTube channel homepage (https://youtube.com/@bchtechnologies). Use the search function near the "About" tab to find specific troubleshooting videos—we’ve published hundreds over the years, and YouTube’s suggestions can also guide you to related content from other experienced creators.

Thanks again for trusting BCH Technologies with your technical questions. We appreciate your commitment to maintaining your equipment and are here whenever you need us!