Colour Issues Laserjet700 MFP M775

[NEILFCNF]

Hi All,

I have a Laserjet 700 MFP M775. All the parts in the printer are genuine HP but I am having an issue with colour printing especially reds and yellows.

See a picture of the colour band prints below.

All supplies are 75% or higher it has a new transfer belt and fuser roll in it too.

Can anyone advise how I can fix this issue.

Many thanks

Neil

[Samrit26]

Hello,

This is a classic color calibration / developer contact issue seen on the LaserJet Enterprise 700 Color MFP M775 series (M775dn, M775f, etc.), even when all consumables are genuine and supplies are healthy. Let’s go step by step — I’ll explain why each check matters, because this model’s color path can be sensitive to component alignment and toner contact pressure.

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1. Verify the color plane alignment

When red and yellow are distorted, it usually means the magenta or yellow plane is not aligning properly on the ITB (Intermediate Transfer Belt).
Let’s run a calibration first — it often restores color density and alignment.

Steps:

1. On the printer’s control panel, go to:
   Administration > Troubleshooting > Calibration / Cleaning > Color Calibration

2. Choose Full Calibration Now (not Quick).

3. Allow it to run completely — it can take several minutes.

Why:
Full calibration recharges the color density sensors and adjusts timing for each color plane (CMYK) against the ITB’s reference marks. When new belts or fusers are installed, calibration is mandatory before normal use.

After it completes, print a Diagnostics Page:
Administration > Reports > Configuration / Status Pages > Print Quality Pages
Check if red and yellow are still faded or uneven.

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2. Check toner contact and developer drive

Remove and reseat the magenta and yellow toner cartridges:

• Open the front door.

• Pull out each cartridge, gently rock it side to side 5–6 times to redistribute toner.

• Reinsert firmly until you feel solid engagement.

Why:
If a developer gear isn’t fully meshed or the toner is compacted, it leads to low density in one or two colors (often magenta and yellow).

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3. Inspect the ITB contacts and sensor windows

Since you’ve replaced the transfer belt, make sure:

• The ITB contact springs (right-hand side of the assembly) are not bent or misaligned.

• The ITB sensor window under the belt (near the primary transfer roller) is clean — even a light toner film on that sensor can cause inaccurate color registration.

Use a lint-free cloth slightly dampened with water (no alcohol) to clean the sensor window.

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4. Run “Color Plane Registration”

From the control panel:

• Administration > Troubleshooting > Color Plane Registration

• Select Adjust Color Registration Now

Why:
This synchronizes the laser timing for each toner plane so colors align correctly on the belt and page.
Misregistration between magenta and yellow directly affects red/orange accuracy.

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5. Check environmental / firmware factors

• Firmware: Confirm the device is running the latest firmware (available from HP Support site under “Firmware – FutureSmart”).

  • Older revisions can mis-handle calibration tables after fuser or belt replacement.

• Environment: Excessive humidity (>70%) or cold (<18°C) can reduce charge consistency, making reds/yellows appear weak.

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6. If still no improvement

Print the “Image Quality Troubleshooting Page” from:
Administration > Troubleshooting > Image Quality Menu

That page divides CMYK patches per plane, which helps isolate which color path is failing.
If either magenta or yellow bands are visibly streaked or missing:

• Suspect HVPS (High Voltage Power Supply) or DC Controller PCA — both control developer bias voltages.

• If both colors are affected simultaneously but cyan/black are perfect, the secondary transfer bias or ITB ground contact could be weak.

Those are not field-repairable without parts isolation — at that point, it becomes a depot-level service case.

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