Welcome to Justanswer.com, my name is ***** ***** I will do my best to assist you.
This is for a similar machine.http://support.brother.com/g/b/faqend.aspx?c=us&lang=en&prod=mfc6490cw_all&ftype3=1964&faqid=faq00000565_011
Do you see where it shows the encoder strip and tells you not to touch it.. Both the paper jam error and the print unable 76 error are from the encoder strip being either dirty, or out of place.
So check your encoder strip and if its bent, damaged, let me know.
if its dirty or slid out of place, try to gently clean it and slide the encoder strip back into place and it will fix the issue.
I strive to provide great service, and greatly appreciate a 5 star rating clicked and submitted when you are satisfied.. I always answer follow up questions.Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.