Drum heater lamps

There are three possible solutions.
Try running the 'remove print smears' routine from the print quality troubleshooting menu. You may have to run it 5 or 6 times to completely clean the drum.
It may be that the drum maintenance pivot plate is cracked, this causes the plate to press the maintenance kit on to the drum unevenly. You will hear a ripping sound as the paper exits the printer, this is due to it literally ripping the ink off the drum. Being an 8400, if your pivot plate (the assembly that your maintenance kit slides on/in to) is white (off white) in colour, my money is on that being cracked.
The third possibility is that the cam shaft that pushes the pivot plate up to the drum has loose/spinning cams which again, will cause the plate to press unevenly.
Hope this helps.

There are 2 ,, 150 watt halogen lamps in the machine that heat the drum. One of both have burnt out.
To verify that, turn the machine on and look into the fan slot and look for glowing lamps. If after a minute or so , you don't see any light in the machine, one or both lamps have failed.

Hi outonalimbwi:
Here is your problem.
37,006.42: PEST - Drum disconnect. The drum heater is not drawing the expected power from the supply.

Troubleshooting Procedure
Step Questions and Actions Yes No
1 1. Run the appropriate diagnostic test:
37,002.47 = Left Jetstack Heater
37,003.48 = Right Jetstack Heater
37,004.40, 37,005.41 = Reservoir Heaters
37,006.42 = Drum Heater
37,008.44 = Preheat Heater
37,009.45 = (8500/8550) All ink melters
= (8400) Ink Melt 1
37,010.46 = (8500/8550) Ink Melt 1
= (8400) Ink Melt 2
37,011.47 = (8500/8550)Ink Melt 2
= (8400) Ink Melt 3
37,012.48 = (8500/8550)Ink Melt 3
= (8400) Ink Melt 4
37,013.48 = (8500/8550)Ink Melt 4
2. Did the test pass?
Go to Step 3. Go to Step 2.
2 1. Check the wiring running from the component to the printhead.
2. Is the wiring damaged or not working properly?
Replace the wiring harness.
Replace in the following order:
■ Drum assembly
■ Preheater
■ Printhead
■ Ink loader

you have to change lamp (or rezistance) heater located under drum ink, down drum film.
if you now what i are saying probably you can do yourself servicing . just ask for your printer model lamp heater (or rezistance). if not get your printer serviced befor destry him.

When you replace the drum open the front door of the machine where thr drum and toner is.
Hit the clear/back button. Press 1
That resets the drum count after you replaced the unit.

No, If one lamp goes out they both will not function. They do not have anything to do with print quality.
You may have a bad maintenance kit. but more than likely you have a bad print head.
Run the cleaning , eliminate stripes and eliminate smears modes. But more than likely the print head is bad. I would say a bad print head is about a 95 percent chance of causing your problem.
The halogen lamps only heat the drum, and if one was bad the machine would fault out with a 15,004 code.

nope its not a drum problem, That drum never goes bad. You are having a problem with some blocked jets in the print head.
You can scroll through your menu to troubleshooting and there are cleaning modes to eliminate light stripes and to eliminate smears.
Run the eliminate light stripes maybe 2 or 3 times. If that doesn't work, then try the jet substitution mode.
That is better described at Xerox.com, click support, then enter phaser 8400 in the search box, click support again and then enter
"jet" in that search and follow the directions.
If those do not work then your print head is most likely bad. Thats more likely if you have used non xerox ink sticks.Being low on ink should only give you a message that its low.

Most of the time it is the paper heater assembly not being hot enough.
Althoug that is a problem most associated with the paper your using.
If heater is out, normally the machine faults out. But still as seen in the documentation , a heater may not be in position or functioning properly.
1
Check the media type and finish.
If the media appears glossy, replace the media and reprint.
Does the problem persist?

2
Check the Preheater and Drum temperatures.
Run the Service Diagnostics Temperature test.
Are the temperatures within specified ranges (approximately 60 to 62 degrees Celsius)?

3
Check the position of the Drum Temperature Sensor.
Is the sensor positioned properly?

Problem:
The machine displays the Replace Maintenance Kit after the Maintenance Kit has been replaced.
Cause:
There may two causes for this issue.

1. The machine does not recognize that the Maintenance Kit was removed. This would likely be caused by a defective Drum Maintenance Pivot Plate.
2. The machine corrupts the CRUM on the new Maintenance Kit. This may be caused by a defective Drum Maintenance Pivot Plate or IO Board.

Solution: Fixed! Did not fix.

1. While the Replace Maintenance Kit message is displayed, remove the Maintenance Kit. If the displayed message does not change to "Maintenance Kit Missing," replace the Drum Maintenance Pivot Plate and install a new Maintenance Kit.
2. While the Replace Maintenance Kit message is displayed, remove the Maintenance Kit. If the displayed message changes to "Maintenance Kit Missing," replace the IO Board and then install a different NEW Maintenance Kit. If the problem persists, replace the Drum Maintenance Pivot Plate and install a different NEW Maintenance Kit.

ETI v1.3.20.0 610606.Replace Maintenance Kit Message after it Has Been Replaced 2007-11-18 21:37:39

The 8400 has a known issue with the plastic that was used for the tilt mechanism on the oiling roller. If you look inside where the cartridge is removed you should see a crack that opens when pressure is applied. The high heat causes this unit to crack. You need that part. Or some good super glue. I have fixed 3 of my 8400's with this same issue.

Good Luck