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HP Recommended
HP Designjet T790

Hello! I'm an agent of the US Postal Service, and I've been tasked with repairing an HP Designjet T790 Plotter Printer we have at site.

Originally, this device was showing an "error 08:18 When printer is restarted, it will not work until firmware is updated", and was not responding to any input, as you can see below: Designjet T790.jpgInitial errorI fixed this by going to HP's website and downloading new firmware (Reference: Support.HP.com was the website I got the firmware from) and moving Firmware onto a USB drive, then migrating it to the plotter using the USB port you can see in the image above.

And it worked. Pretty perfectly. It recognized the firmware, installed it, rebooted it, and everything looked like it would work.

Except now the dash shows "Initializing: 20%" and won't proceed beyond that:

I did some research. Some other threads that talk about this device freezing at 94% suggest turning device off, removing paper, print heads, and toner cartridges, and then turning it back on and reinserting these bits when the printer prompts you for it. I tried that, but the printer never asked for these materials to be reinserted. It just froze at "Initializing: 20%" again.


I also tried removing the formatter, turning the device off, then removing the two screws on the lefthand side of the device and removing, then reinserting it and tightening the screws again. Upon powering the device back on, it did the same thing. Still no luck resolving that.


Lastly, out of desperation, I tried initiating a master reset using a method recommended to me online, pushing the buttons of "Cancel, Home, then Help" on the digital dashboard in that order, when it first starts up and the buttons light up. This also didn't work, the device did not respond.

So I'm a bit out of ideas at this point. Any suggestions for how to fix this issue?


Information regarding this device:

The Serial Number is [edit]

This device is on a network

It cannot be pinged, nor can I access an Administrative page for it online.

HP Recommended

If you do a google search for the Designjet T790 Service Manual, it should bring up a link to it that you can download.


This is what I've found in the service manual:


If the printer freezes while initializing, the following explanation can help you understand at which
point of the initialization process it stopped and what could be the cause of the problem:
● 1%: This is equivalent to a system error 08:11, perform the troubleshooting procedure for 08:11.
If there is a communication failure between the Touch Control Panel and the Engine PCA, the
following message will display “Time out initialization”. If the communication is lost for more than
24 seconds, the system error 08:04 might display. In this case, perform the troubleshooting
procedure for 08:04.
● 2-20%: Initializing Touch Control Panel. If the printer freezes between these two percentages,
replace the Touch Control Panel see Touch Control Panel on page 547
● 20%: Linux Operating system starts up. From this point on, other parts of the printer besides the
Touch Control Panel could be causing the problem.
● 32%: Communication between the Touch Control Panel and the printer is checked again. If the
connection fails it might show system error 08:04 but it might be hidden and just freeze. NVM is
also initialized at this point. If the printer freezes at this point, check the HDD, Encoder PCA and
Touch Control Panel, and follow the troubleshooting for system error 08:04.
● 34%: Initializing printer I/O. If the printer freezes at this point, try starting up without any external
connections (USB/network). Usage counters are initialized. Replace HDD, see Hard Disk Drive
on page 389 and Formatter see Formatter on page 381.
● 94%: Initializing printer processes: mechanical movements, sensors, scan axis, web server. Start
the printer without printheads, supplies and external connections. Parts to be replaced are multiple
at this point, please check what the printer is doing just before it freezes to get more information
about what could be failing.


You might not have to replace the touch screen.  I'd try unplugging and replugging it first.


Hopefully that will help.  Let us know how it goes.

HP Recommended

I unplugged and plugged the cords to the touchscreen back in, but no luck. T.T

Still, it was a very useful suggestion, and I didn't have a copy of the service manual, so thank you for cluing me into it's existence.

Anyone have any other thoughts, or should I look for a replacement touch screen?

HP Recommended

The master reset should start with combination of Cancel -> Home -> Eject try that combo to see will it enter Diagnostics menu.

You can get a free service manual for download.


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HP Recommended

It's very unlikely that it is a control panel issue, I would place my bet on failed HDD. The HDD contains data like on a computer, and it's not loading printers operating system from HDD.

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