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Hp designjet 500 plus firmware upgrade A.05.01 problem

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Hp designjet 500 plus
Microsoft Windows 7 (64-bit)

Hi there! Just upgraded Hp designjet 500 plus firmware after error code 79:04. Used the firmware upgrade tool for windows and, after installing, the printer is no longer recognised via USB with the "Unknown device connected" message apearing every time.

Does anybody know how to fix this?

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Can you access to the FP?

if yes : perform EEROM Setup then install the firmware following below article :


I am an HP Employee.
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Check the print head Guaranty date. If all print head are out of guaranty. Change all and that is it. Believe me. 


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