Need Help Mystery JV300 - yellow head channels won't print

hybriddesign

owner Hybrid Design
Hi Everyone, I've got a mystery JV300 issue and this is actually the second time that this happened.

Our JV300 is running the 2L sublimation bags and using Mimaki ink.

About a year ago (1 month after the warranty expired of course) the yellow ink ran dry in both heads due to a incorrectly seated ink bag. We couldn't get the yellow channels to work again no matter what we did. Hard ink fills, new capping stations, etc, nothing worked. The most obvious answer was a problem with yellow ink delivery, lines, solenoids, etc. The strange thing was that if we pulled the ink lines from the dampers we could pull yellow ink via a syringe. Then we swapped dampers around and yellow ink prints just fine out of the magenta head channel but we can't get magenta to print out of the yellow head channel so it seems to be the head that's the issue and not the ink delivery.

We ended up buying two new heads and after 3 hard fills it worked.

Now 6 months later we've got the same issue. There was no unseated cartridge but the yellow dropped in both heads and again, new capping stations, trying everything we can and we can't get the yellow to print. BUT after swapping the ink lines yellow prints just fine out of other head channels so again it's a head issue and not a ink delivery issue.

Does anyone have any ideas on this? The JV300 is in excellent condition and we used it minimally but and I'm trying to figure out if I just give up and buy a new printer or keep trying on this. I don't really want to buy a two new heads... Debating giving up and switching to either an Epson or one of the newer Mimaki sublimation printers. We have 2 other mimaki's btw as well as other printers and I'm pretty well versed in working on the printers. This just has me stumped as it seems almost like a circuit board issue or something.
 
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