Error 79 on hp printer?

79:xx Error- general firmware error- look at this fault the same way you look at windows blue screen of death - theres usually noting wrong apart from corrupt data in a print job- disconnect the printer from all network sources cycle the power with no network connection to clear fault then clear all print queues from the workstation (PC) before reconnecting network. also you might want to try a config page print test before reconnecting network..
if unfortunately the printer will not come to ready when the network has been removed, then the formatter is likely to be the cause .

79 errors are often fatal. Your only hope is to get it back to READY, then update the firmware before it reverts back to 79 ERROR. The other option is to replace the formatter, but it would be about the same cost to replace the whole machine.