Mutoh VJ 426 adds yellow to prints

[aboostani]

I'm using a Mutoh VJ 426 to print gifts on different materials like iron, copper, wood, and fabric. The printer started adding yellow to the design sometimes in places that even didn't have a design.
- We had a technician change the CR board. But after a day, we noticed the problem is still there.
- The printer works ok when there is light usage. When it's being used more heavily and it prints larger items, the problem starts again.
- We noticed when the problem starts, after the printing is over, the fan (not the suction) stays on for ~20 seconds instead of the normal ~3 seconds. We've also felt inside is warmer than usual.
- When we send the nozzle check test, the yellow prints are half correct and half a full block of yellow.
- Since we don't see spots on the prints, we think the problem can not be the head but I almost don't know anything about printers and would love to get your input on what could be the source of the problem.
- I've attached some pictures so that you can see the problem.

Really appreciate your help to diagnose the problem.

 

[netsol]

check/change ribbon cables
BE CAREFUL.
fully power down, unplug machine WAIT 15 minutes for capacitors to discharge

lets not turn this into blown fuse/shorted transistors

i think any time you disconnect a ribbon cable to check it, you might as well replace it

we had an issue on my sc545-ex where one of the yellow canles had a burned. spot. one of the straps that holds the cables flatbwas loose, (yellow is on top) and was just touching a piece of metal at the far end of carriage travel

 

[Solventinkjet]

I agree with above. You have an electrical issue and it's usually bad cables. It could be a failing head and/or other electrical part though.

 

[netsol]

I agree with above. You have an electrical issue and it's usually bad cables. It could be a failing head and/or other electrical part though.

hopefully just cables, although i have had 2 different heads on my sc545-ex go bad that way

 

[aboostani]

Thanks @

hopefully just cables, although i have had 2 different heads on my sc545-ex go bad that way

Thanks, Netsol for the suggestion. Are the ribbon cables the flat ones that go into the head?

 

[unmateria]

Yes, i agree too. Try replacing those cables first (the flat ones to the head). Look the connectors are ink free and connect them with no force at all.