My 7900 had been idle for a bit less than three weeks when I received an order from a client to print five of his panoramic images. To start, I printed a nozzle check, as usual. It was perfect. Based on past experience (see my 4 April 2013 posting for an example), and the experiences of others as related on various forums, I waited about ten minutes and then printed another nozzle check. This showed some missing nozzles at the top and bottom of the LLK pattern.
I did a standard cleaning of the LLK/Y pair and then printed another nozzle check. This time, nearly the entire LLK channel was missing. Lovely when a cleaning makes things worse. I did a second LLK/Y standard cleaning, printed another nozzle check, and found no improvement. Finally, after a "powerful" cleaning of that pair, the nozzle check print was perfect.
After that wasted half hour, I printed the client's panoramas, finishing off a 24 inch roll of luster. (By the way, if you've not finished many rolls of paper while printing, here's what to expect: I was standing in front of the printer. The last image had nearly finished printing. Because the printer's roll cover was closed, I could not see the roll. I was startled by a loud "FWOP" sound from the printer, not a noise I normally associate with printing. The print finished as usual, and was cut from the roll. After my heart rate returned to normal I realized what had happened. The end of the paper had come off the roll and whipped against the inside of the roll cover. I knew the roll had just a little more paper left than necessary to finish this print, but hadn't expected the loud noise. No harm done.)
Three days later I made two large prints and several smaller ones of my own work for an exhibit we'll hang next week. I made the nozzle check print, found no problems, and then proceeded to set up and print as usual. There were no problems at all with this print run.
Bottom line: It seems if the 7900 is idle for "a while" (intentionally vague, as I suspect "a while" is quite variable), the first nozzle check may be 100% OK. However, it may be that this uses ink readily available at the nozzles, within the head, very nearby in the ink lines, or otherwise close to the nozzles, and consumes most of that tiny reserve. If a print is then made right away, it won't be acceptable; you'll have wasted time and a sheet of paper. If, instead, a second nozzle check is printed, it will point to the channel(s) which aren't receiving ink. I think this points to an ink delivery problem, rather than nozzle clogs. Perhaps it's air in the lines, as some have speculated. Nobody really knows, of course, leading to lots of guessing and misinformation. In any case, cleanings do eventually clear the problem.
When the printer is used more frequently it seems this issue is avoided. Friend Dean, with his 7900, has reported exactly the issue described above, with the same ink channel (LLK) being problematic. Similar stories abound in the forums.
This has led people to invent test files, designed to print from every channel, which they run periodically (often daily). Some have gone so far as to automate the process. Doing this works for some, doesn't for others, leaving us exactly nowhere with a solution.
Mine is to print a nozzle check, wait several minutes, and then print another, if I think my printer has been idle for "a while". I can then deal with missing nozzles, or get on with printing if there's none.
--Jay
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