JV 33 printhead began printing wrong color

I'm searching throught the past forums for answers but wanted to see if anyone has suggestions in the meantime. MYJV 33 printhead began printing the wrong color on one channel. In the middle of printing - it looked liek yellow had dropped out. I stopped the pring and did a test draw - all nozzels fires except one of my yellow blocks is cyan now.

Ink is full - I've cleaned everything and performed multiple nozzle washes and the usual. No luck. I can get maybe 1/2 to turn yellow but they quickly go back cyan.

Any ideas?

 

I let ran a nozzle soak for 4 hours - still no yellow. I replaced the capping station a couple of months ago so it's pretty new, and I just replaced the yellow damper last night to see if that took care of the problem. Before I pulle the old damper I could see the tiniest bit of green inside the yellow damper. After I replaced the damper half of that channel printed yellow for a couple of test prints while the other half remained blue. Now all I am getting is 100& cyan firing from the yellow channel when I perform a test print.

In the pic - the pen marks where I should be seeing yellow. It's printng as if it is a cyan channel.

It looks as if the problem is below the dampers. Mimaki says someone had to put the wrong color cartridge in the yellow slot but I can't see how that would be - if someone inserted the wrong cartridge I would see some shade of green firing in the test print - not 100% cyan. I've checked the lines anyway when I changed the damper.

I'm at a loss - can the contamination be coming from inside the head assembly (below the damper) and what could cause this?

 

Thanks for the tips - of course it happened at the worst time possible. I'll keep trying!

 

It turns out the head was shot. Using a syringe a purged cleaning solution through the yellow damper and into the head - being careful not to apply to much pressure. The fluid never cleared up it just kept leaking cyan. The baffle, or gasket between the cyan channel and yellow channel in the head was broken.

Luckily Mimaki's office is close to our shop. I just finished replacing the head and recalibrating the machine. Finally - it's printing again.