so lately im having issues with an 4000 inkjet plotter.
the plotter has 4 ink stations and 8 printheads to work with. the ink station has 4 relatively full bags of ink.
the carriage has printheads new and old oldest must be dating from end 2017.
it was working just fine until a few months back when i started noticing a few things were going wrong.
the plotter would print but it would calibrate itself right when asked to.
calibration reported cancelled due to scanning issues etc even though all patterns were printed.
plotter would print b/w autodesk drawings and would stop half way mentioning a black printhead error.
both sensor and printheads were replaced with brand new ones. though problems went away for a while they quickly came back worse. long story short the printer was still having problems spitting out 79:04 or 21:13 occasionly. techs came and went not finding out why this is happening. in the meantime something odd is happening. i began to see small air pockets once every now and then in the tubes, which prompted a really close examination of the printheads. apparently, some are still recognised as hp printhead blah blah, but they are wayyyyy too light. it seems that although the printer looks OK it isnt.
there is no ink flow form the station to the head. the printer is using the small amount of ink in the head while its new, and somehow wont flush it with new from the bag. when the ink runs out, the problems begin. this happens with original and not ink bags. new or old firmware. new and used heads. trying to research this mystery, i got the service manual for it and a new tech. the tech guy says we should just re - replace printheads (a cost of several hundred euros only to repeat the error in the future) and the on site service tests the printer has all show up to PASS.
there is even a test to pressurize the system and this passes as well.
as an attempt to call hp directly to have an actual tech guy from the company guide me through, they gave me company X, which is an authorised service center, who came over, did the same exact things as me with no solution... oh yeah, he also wanted payment of about 130 euros per hour just to tell me what i already know.
for now, the printer, boots up with no error at all but when something is sent to print no matter the mode it sends out a 79:04 which is just a generic error.
any ideas, other than "replace printheads"? seriously, with what they cost, i would rather buy a new canon or epson.....