During the two months that lasted my attempts to resurect my 4900, I had it moved onto a clear area, where I could freely take it apart. Now that I received 6 new 200ml Epson ink cartridges, I reassembled all the covers and proceeded to move it back to its place in my office. All the days leading up to my "pledge of allegiance" to Epson, deciding to plough $600 for 6 new ink cartridges, I kept printing spotless nozzle checks.
But right after moving it back to its original place, after loading in the 6 new cartridges, Photo Black started to act out.
I tried different cleanings, not strong ones to begin with. So I did 4 or 5 normal ones with marginal improvements. I then tried one power cleaning, just on the BK/pair. No improvements. Hmmh, I thought. I was beginning to entertain the thoughts of, what, opening the printer again but instead, I let it sit there overnight, and shut it down. That was on a Friday night, late.
The next day, Saturday morning, I flipped the power switch on the printer and tried my luck with another Nozzle Check : perfection!
And it has stayed that way ever since. I now make sure I print everyday, without fail, to the printer, if only a nozzle check or a small image, just so that I keep the lines active and the head alive.
Will follow up at a later date...