M750 no yellow

[redcow]

A buddy of mine is troubleshooting an Enterprise M750. Starts printing good. After a few pages the yellow drops and all yellow printing is now white in appearance.
Here are the parts that have been replaced so far:



Toner drive motor
Formatter board
ITB
Scanner Assm
DC controller

When cartrtidge disable test is run, the cartridge in the yellow slot starts out good and then "white".
There are no error codes or messages.
Firmware is up to date.
I'm leaning towards one of the HVPS - primary or imaging.

Any thoughts??

[ptjeff1]

I'm assuming you tried a different toner in the yellow slot and got the same result?
Our lead tech is on vacation right now otherwise I'd ask him if he has seen this; we usually find these are mechanical problems, e.g. solenoids sticking and failing to engage an assembly, bad ground or HV contact, broken linkage, etc. Also, make sure you don't have 2 bad ITBs.