I have a printer given to me that does not print properly from the black print
head. There are regular horizontal gaps in every printed head, which I think
indicate plugged jets in the print head. I'd like to manually clean the face of
the head with ammonia water like I have previously on other printers, but this
unit does not seem to offer any easy access to the actual print head. Can anyone
suggest the easiest way to get to it, perhaps with a cotton swab?

I have tried multiple cleaning cycles, and printing pages of all black with no
improvement. They print well except for about 1/8" gaps horizontally every 1/2".