Don't want to drive you away from proon but you might like to post this on...
www.experts-exchange.com
One of the guys on there - Keith - designs the electronics for HP deskjets.
I have his email address at hp.com but you might be better going through the forum so as not to abuse the system.
Failing that, buy an Epson.
Used to have an 870cxi for business use. Too expensive foro the amount of paper I used. Smacked it with a 2lb hammer & threw it on the tip. Bought Epson laser & inkjet and running costs shrank by over 60%. To buy a new printer is same cost as 5 or 6 HP cartridges.