To my joy I noticed that my HP LaserJet 4250 had an ancient FW. Not that the newer firmwares provided anything useful in my case. Neither bugfixes for bugs that I was hit by, or features that I longed for. The process of FW upgradinga HP LaserJet 4250 to a newer FW is actually quite simple. Here goes
zensonic@x230:~/Downloads$ ncftp 192.168.1.242
NcFTP 3.2.5 (Feb 02, 2011) by Mike Gleason (http://www.NcFTP.com/contact/).
Copyright (c) 1992-2011 by Mike Gleason.
All rights reserved.
Connecting to 192.168.1.242…
FTP Server Ready
Hewlett-Packard FTP Print Server Version 3.0.
PORT hp LaserJet 4250
To print a file use the command put <filename> [portx]
or ‘cd’ to a desired port and use put <filename>.
User logged in.
Logged in to 192.168.1.242.
ncftp / > bin
ncftp / > mput lj4240_4250_4350fw_08_250_2.rfu
lj4240_4250_4350fw_08_250_2.rfu: ETA: 0:00 16.68/ 16.68 MB 277.63 B/s
And then the printer rebooted yielding.