Seems there is a problem with the cartridge retaining mechanism on the 7150
/ 5550 printers after going thru' 3 printers 2 7150's and a 5550 the problem
persists.
If the #56 or the #57 catrs are inserted genlty and latched properly the
sceanrio is the cartridge(s) are either faulty ie the carriage parks at the
BAD position with priner lid up OR are accepted but the 4 3 tap test shows
missing nozzle

((
IF when inserting the #56 or #57 you apply firm pressure so the contacts
are made firmly ie push the cart. against the cadel firmly and then close
the latch all is well

Seems to be an inherent design problem here
Compared with the 9XX series printers the latching contact method is FAR
more Reliable
Great printers the 7150 and 5550 but something is wrong here.