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HP Recommended
Designjet T770 (Hard Disk Version)

I replaced an empty printhead, but the printhead replacement kept failing. The new printhead was again replaced, and it seemed to work, but then machine kept giving a 79:03 error whenever tried to print. After following a few troubleshooting guides I recalibrated the printheads, and then got a error message indicating that a diffrent printhead (that was working previously and was installed 2 months ago) needed replacing. 


I then did a diagnostics test and during the Carriage Assembly Test after removing the printheads (as instructed at that point) the machine gave the error message: ERROR_FIRMWARE


At this point I restarted and updated to the newest firmware on the HP Website with a USB. After the firmware was installed and the machine restarted the error message now showed that the printhead replacement was unsuccessfull.


Please assist!


HP Recommended

Hi,  Thanks for contact with HP Support Forum.



Please unplug the USB/Ethernet cable and perform the below instruction:


                Please download the below link file.


1st Steps: https://support.hp.com/us-en/drivers/selfservice/hp-designjet-t770-printer-series/3980523



Firmware Update Process:


2nd Steps:


  1. The Thumb Drive Plug-in with your computer/laptop.
  2. Format it your Thumb drive on FAT32 (Default)


3rd Steps:


  1. Printer Firmware send into Thumb Drive (Your downloaded file, on 1st steps file)
  2. Unplug the Thumb Drive from PC/Laptop


4th Steps:


  1. Plug in to with your Printer Font Panel or Printer Back side where have to on printer left site. At this printer should be turn off.
  2. Turn on the printer and wait some few minutes.
  3. After some time printer shows it “Update the firmware” on printer control panel.
  4. Click on “Update the Firmware” button on the touch control panel.
  5. After few minutes printer control panel shows it “Un plug your Thumb Drive”
  6. Just unplug in your thumb drive from Printer.
  7. Just wait few minutes for firmware update issue. (After few minutes printer will automatically restart)
  8. After initialized the printer, it automatically came to ready mode. (If raise the any other issue or error, please call to me for below cell no.)


N.B: While update the firmware, please do not turn off / interrupt the printer. So you need to use backup power like: UPS.



I hope that answers will support to concern adequately. Let me know! Good luck 

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