HP Scitek FB700 Not printing Light Magenta - Replaced thermistor, ink in reservoir - still nothing

[MarkH42]

About 3 days ago the light magenta color stopped printing on our FB 700. Both LM heads stopped immediately and went from firing almost all jets and a near perfect jet health test to zero. The fact that both went out at the same time steered me away from it being the print heads. Initially I replaced the light magenta thermistor with a used one and that didn't help. When you purge or attempt to fill the ink head, light magenta ink comes out of the heads as it should. There is no error message saying the heads didn't fill. When I look inside the thermistor, it is 2/3 - 3/4 full of ink. I ordered a brand new HP thermistor in case the used one was bad, but that didn't help. Vacuum pressure is steady, so it doesn't seem to be a vacuum leak. But a jet health test is completely blank in the light magenta area. A printhead recovery procedure on light magenta is blank also. I am stumped. Any ideas? Thanks in advance for the help!

 

[danno]

It's been awhile since I have operated or worked on a FB series. Check for a white UFO looking filter under the head cover. If memory serves me correct, that filter with clog and not allow the vacuum into the head.

 

[MarkH42]

I know the filter you are referring to, but unfortunately I don't have a replacement. I suppose I can take it out completely just to test the theory......

 

[sonnyphoto]

test your connections to the main board for the print heads