Need Help Very fast partial nozzle clog SP300V

[Ecoline]

Hello
I run a pretty old (14y) SP300V which had his first printheads until last week. I replaced both the CK and eventually also the MY Printhead, which worked perfectly. I also changed the Dampers, Wipers, Scraper and both Captops with Roland OEM parts, and the pump is also visibly working (even inkflow is noticeable from both caps, replaced the tubes with clear ones to be able to check that). Nozzle test is 100% without any deflection or even missing nozzles. Running OEM Roland ESL3 Ink in all heads which is NOT expired.

The problem is:
the M row is operating fine, as long as its printing. The moment i shut of the printer overnight and run it the next day, some of the Magenta nozzles show significant deflections. Its not the same nozzles everyday, they interchange.The only remedy for this a thorough manual head clean or 1x powerful headwash.
Its ONLY on magenta, yellow running in the same head and nozzleplate is not showing this phenomenon. The time it starts to gradually show up is about 6-8h without printing. Both printheads are genuine replacement parts and visually show no defects ( microscopically on the nozzleplate) Ink tubes are also fine ( tested with a syringe, no bubbles no leaks, oring at the dampers are changed). They were no head strikes or similar events.
The deflection on the nozzles are so bad, it sadly affects the print quality. poor perfomance for a mint head with 3000kShots.
Can i try to change the Y and M line on the head to rule out any other things then the head?


i run out of ideas what to do, may someone help please

 

[damonCA21]

There are a few reasons can cause it. It could be the captop is not sealing against the head properly, allowing it to partly dry out. It could also be an ink supply problem to the head. This can be from a bad cartridge, partly blocked ink line or blocked needle in the cartridge dock.
When you changed the dampers, did you also fit new o-rings onto the ink lines as these can cause small air leaks. Also check very closely the head manifold as these can easily crack and let air into the head when it is sitting idle
The easiest way to tell is to swap over the lines to the head. Unplug the dampers and swap the whole thing over. If the problem moves to what used to be the yellow head ( that is now connected to the magenta supply ) you know it is a problem with the ink supply, if the problem stays with the magenta head you know it is a cap top problem

 

[netsol]

and, as vanderj often tells us, be sure to cut 1/8" off each hose as you replace the orings

 

[cornholio]

On such a old geezer, there could be a pinhole in the tubing. (Roland suggests to replace it after 3000h printing time.)