HP T790 comes up to 20% on power up and returns 79:04 error

[lh72]

Hi

I have the HP T790 plotter, model number CR649A. The plotter hangs at 20% when opening and then returns the error 79:04. I closed the plotters a few times and the problem continued in the same way.
Condition of the lamps on the shaper:
lamp 1 - flashing
lamp 2-on
lamp 3-on
I tried removing the printheads and print cartridges, something hasn't changed.
While opening the plotter, I made the cancel-home-help key combination. After that, the plotter file system checks and finishes and comes to the same place and returns the error 79:04.
I plug the usb stick into the plotter for software installation and it does not install and gives the same error.
I removed the formatter and installed a new battery, the same error persists.
Can anyone help solve this problem?

[Valsimot]

The 79:04 is related to firmware error.

When you removed formatter there should be HDD on formatter board, that HDD contains LINUX system and firmware, and that HDD is very likely to fail.

Now the bad part is that you can install any HDD instead old one, you need to install HDD that already had firmware on it, you can find them on eBay.