D081 Aficio C6501 light pale yellow background

[stephend]

It looks like you don't have any luck with this new machine.
Last week the preflight tech asked for my help regarding a brand new MPC 6501 that he was preflighting it. Everything went OK, he preflighted the machine, tested it, ran the ACC & CR and he turned off to install the fax unit. He installed the fax unit, tested it and after he placed a color chart on the glass to do some test copies.....Surprise...everything was good except...a complete light yellow background...He couldn't believe his eyes, tried more copies, on different formats...same thing. He sent test prints from computer and he tried internal print from the engine....Everything had this background light yellow.
I attached pictures to see exactly what was going on. Will be 2 copies of the C4 chart, one good with no background (after the fix) and one with the yellow background. The reason I placed them one on top of the other is to be able to see the difference.
Machine recorded the following SC codes 439 (15 times), SC 496 (2 times)
Last Procon was 99999916.

I checked and cleaned with alcohol the MUSIC sensor, checked the Y unit, reinstalled everything and I redid the 3820-2....and the problem run away.
The SMC's before and after are way different regarding the TD sensors in 2263 Vt 0.75 (Y) and 5.00 after.
Same major differences in the Potential sensor values.

[E Winter]

Strange - I'd say that something went bad during the ACC but the yellow scale on the faulty test print looks fine (as far as I can see it on the photos). I'm still amazed how sensitive these machines are. Even a "trial and error" TD init or a non-successfull dev fill may break your neck.

[stephend]

You are perfectly right Jan,
something definitely happened during machine calibration or better said during the first auto process control because the first prints and copies were perfectly OK.
When my coworker called me and I printed the first SMC report I saw TD Vt for every color out of wack ~0.80V. Same thing about the potential values. Everything went back to normal after I cleaned the MUSIC sensor with alcohol (was not dirty) and redo all the calibration process starting with a forced manual Procon with density adjustment.