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How to Fix OKI C711dn Error 390 (Transfer Belt)

Error code 390 on the OKI C711dn indicates a transfer belt unit error. It is triggered when the internal control system fails to detect correct belt speed, calibration markers, or proper physical installation.

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Common causes

  • 1Dirty or oxidised copper contacts on the transfer belt or the internal spring pins.
  • 2Toner dust coating the reflective optical sensors inside the printer.
  • 3Drive gear slipping or broken drive motor linkage.
  • 4Physical wear, stretching, or misalignment of the transfer belt.

Solutions

Diagnostics and Resolving the Transfer Belt Error

The 390 error usually stems from dirty contact points on the belt assembly, waste toner obstructing the reflection sensors, or a mechanical clutch failure.

Step-by-Step Technical Instructions:

  1. Power Down: Turn off the printer and pull out the power cord. Let it cool down to avoid contact burns near the fuser.
  2. Remove the Belt: Open the top cover, extract the four drum/toner cartridges (keep them in a low-light area to protect the drum surfaces), and lift the transfer belt out using its designated handles.
  3. Clean the Contact Pins: Use a lint-free cloth or a cotton swab dampened with isopropyl alcohol to clean the metallic connection plates on the left side of the belt unit.
  4. Clean the Reflection Sensors: Locate the small optical sensor lenses inside the printer chassis beneath where the belt sits. Gently wipe off any toner dust.
  5. Check the Gears: Manually rotate the drive gear on the belt unit to ensure smooth and uninterrupted belt movement.

Steps to follow

  1. 1

    Safety First

    Turn off the OKI C711dn and disconnect the main power cable from the wall outlet.

  2. 2

    Clear the Drum Path

    Open the top cover and pull all four drum units out. Store them safely away from direct light.

  3. 3

    Inspect and Clean Sensors

    Remove the belt unit. Carefully wipe down the copper terminals and the optical sensors located on the floor of the printer using a dry, lint-free cloth.

  4. 4

    Reinstall and Test

    Slide the transfer belt back until it clicks firmly into place, reinsert the drums, close the cover, and power up the machine.

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Frequently asked questions

No. This is a hardware status error. The main controller board must read valid sensor signals from the belt during boot-up to clear the status.

If cleaning the copper contacts and optical sensors does not clear error 390, or if you visually notice tearing or wrinkles on the black belt surface, a new belt assembly is required.

How to Fix OKI C711dn Error 390 (Transfer Belt) | Vimazdev