mpc2800 no yellow on prints (rest ok), no error codes

[Mark Bbb]

All colors fine, but no yellow is on the print out.
Toner level indication is at 2 and there is no "add toner message" or ID error code error.
In fact i have checked VSG and VSP and they were fine!
Performed "music" and at the end of it it displays: "failed".
Have cleaned and checked the pcu and developercase, seems fine to me...
The machine was delivered a year ago, but the owner sometimes doesn't print for many months.
Yet, this machine is always in stand by (at power save).
Could that be a issue?
Greetings

[Zeldaman]

Hi there!
Check the ITB-unit, maybe a broken wire, or the roller for yellow is out of position.
Greetings...

[FrohnB]

I agree with zeldaman. Take the transfer belt off of the ITB unit, and look for a broken wire. The one time it happened to me was also missing yellow, and the wire for that had been rubbed and exposed.

[ccchuah]

check the magnetic clutch of the yellow PCU also ..

[Mark Bbb]

After swapping the pcdu it worked fine, untill now...

[Mark Bbb]

Hi there!
Check the ITB-unit, maybe a broken wire, or the roller for yellow is out of position.
Greetings...

I have swapped the pcdu and it worked fine for a month. Now i have swapped the ITB unit and again, it is working fine.
I have taken off the belt of the "bad" ITB unit and i can't see anything wrong. I think you mean with "wires" the white ground wires? They are all in good place and not broken nor twisted. Also the ground plates are in good position. The only thing i can think of is this:
1. the downward movement of the ITB plate to the colour pcu's of the ITB clutch might not be "down" enough (gap).
2. the grounding plates on the left rear side of the ITB unit (one of this two must be removed in procedure to remove the belt) might be at the wrong position. My service manual don't mention the wright position of these grounding plates. Are they underneath the metal removable bracket?
Anyone?