for the longest time printer techs have had a general "tune up" rule for printer repair. similar to when you take a car in for diagnosis. and the mechanic says "let's give it a tune up to eliminate accumulative issues", etc. dampers, wipers, cap tops, etc have been the norm for a pre-diagnostic approach. as well as replacing entire pumps when "rebuilding" only requires replacing a tube that runs through the pump (the pumps are peristaltic). these "tune ups" amount to the demons in each individual printer never being understood. by swapping pump lines, dampers, cap tops, and data ribbons the exact source of the ink supply or data, ... whatever can be pin pointed. whether a printer owner does or doesn't repair the printer, it's good to know the basic fluid dynamics of the machine. when you do get to know the printer, you will see how truly unmagical it is that the ink makes it from the cart' to the jet. and or to the wast bottle. understanding these basic principles will help a printer owner much faster discern just why his machine is clogged and get back to printing. the print test pattern can tell if you have a seal issue, cracked manifold, clogged head, bad capping assembly, bad pump, bad data, bad ink.... just by looking at the pattern. it is the finger print of the machine's state of being. i've found that many techs don't know how to read these tiny clues to the issue at hand. being certified as a printer tech doesn't mean that you are a printer guru. there's only so much training a person can receive in a certification program. the rest comes from that thousandth repair.
as for signs101. if someone does have a pritner out of warranty. post a question there. you will be immediately helped by guys that have long since fired their printer techs.