My 9900 is now six years old and has been used for less than 100 44X30 prints a year.
I used to get the occasional clog that would go away with one or two cleaning cycles, and an occasional power clean. I admit I sometimes did not print for two weeks or more. On this occasion it was probably a month since I printed anything.
Now I get banding which is subtle but definitely there especially in gradients like sunset/sunrise or if there is a single color that is predominant. Nozzle check shows variable number of nozzles that are dropped from 6 of the 10 channels. I ran multiple cleaning cycles in pairs and even through the maintenance mode, the nozzles are still dropped but they are never the same, sometimes it is only 4 or 5 missing sometimes it is as many as 20 in a single channel.
I figured it is not a clog. Cleaned the wiper, did the paper towel and ammonia trick, read all I could at Eric's site (myx900.com) and elsewhere. I thought it is air trapped in the channels so I did single color purge prints at maximum quality, 2880dpi for each channel. What is interesting is that on the purge prints, there is slight banding in the upper 1 inch (I did 36X5 inch prints) of the suspect channels, the rest of the print is absolutely fine. After doing several such purge prints, a nozzle check shows the same variably missing nozzles.
I ran the AID test in the Maintenance mode and it does give the NG error on the nozzles.
To me it seems that when a particular channel is called for, there is misfiring or leak or whatever initially and then it prints fine if forced to do so. In normal prints though, there is usually no sustained demand for a particular channel hence the banding continues to happen.
I've changed all the suspect carts, shaken them and replaced them but it's the same issue. I tried the paper clip thing to see if I can release trapped air, but nothing comes out, not even a drop of ink, don't know if that is normal.
In my limited knowledge, it is not the ink carts, probably (hopefully) not the head, but something in the ink supply somewhere.
I've read that the dampers/ink selector need to be changed every 2-3 yrs, mine are the same from 6 yrs ago. Does it seem like this may be the issue? If so, I can hopefully change the parts myself.
Thanks in advance
Pradeep