2 Canons, MP272 and MP495
Both unused for years, both the same total lack of yellow printing. ,
either m/c even swapping carts. Folded tissue dampened with cleaning
fluid, pressed against the nozzle plate, suggestive of not being a
lock-in "fault".
2 minutes in an ultrasonic bath ,canted over to the yellow side, in
methylated spirits. Both now fine photo-grade output, with refilled carts.