Yellow suddenly missing, print-head is fine

[bauatelier]

We have a recurring problem with our T790 (secondhand, out of guarantee), where the yellow simply and suddenly disappears in the middle of a large print (after 80 cm or so). When plotting narrow formats like 90x30cm, then typically the first two will be fine and yellow will fail during the third. If we turn the machine off for the weekend (and do absolutely nothing else) it will usually be fine on Monday morning - for the first 80 cm or so.

There is plenty of ink in the cartridge, which is nearly new (well within its expiry date). Genuine HP ink too.

Print-head nozzles are all fine. The test diagnostic print from HP Utility (mac) is absolutely error-free, not a single spot or splodge or stripe anywhere in it — except that sometimes all the yellow is missing.

It seems like the plotter "forgets" to pull yellow ink from the cartridge.

Has anyone seen this before? What is the cause, and what is the solution?

Thanks in advance

John / Bauatelier Architekten

[jasonmiamifl]

Your yellow printhead is not fine, if missing color, even you have plenty of inks.

Do a printhead alignment test  or do a diagnostic print... you will know right away.

[bauatelier · Accepted solution]

Sorry for the delay in replying.

Diagnostic tests were always fine a day after the yellow failed, which is what puzzled us. In the end we said "WTH" and just bought a new printhead, and the problem seems to be solved.

Thanks for the tip.

[jasonmiamifl]

Be cautious, you might better check the yellow inktube with syringe & make sure no air inside. use a syringe to draw out ink & make sure no bubble.

if inktube has air & printhead could not get inks. With new printhead, printer might work , then ink inside dry up & problem
again start up.

I messed up a brand new expensive m/y printhead few days ago.  see my recent post. I still can not fix it yet.