Recently my TR8660 started missing horizontal black lines. Cleaning the PGBK ink fixed it for a time, then if the printer wasn't used for a few days the missing lines came back until another clean was done.
I've changed the PGBK ink cartridge (genuine Canon) and done a clean and deep clean, aligned the print head both automatically and manually. There are still horizontal streaks about every inch - even the head alignment instruction sheet had streaks through the printer pictures at the top.
