System Fault Shutdowns

One of the most elusive problems in the Docutech Family of system printers is the PO6-250/251/357 system shutdown fault because there are so many things that can cause this condition in the system. Hopefully you have the latest copy of the field service manual as your reference guide and you have followed the RAP to its conclusion and replaced any components that have failed. If the PO6-250/251 is still present, then we have to drop back ten yards and punt! Keep in mind that PO6-250 indicates that at least one Start of Scan signal was missing and/or not detected by the SOS PWB, and PO6-251 indicates that at least one End of Scan signal was missing or not detected by the EOS PWB. Replacing these boards, in most cases, will not fix the problem. Remove the top cover and check the video cables, making sure they are properly connected to the PWB and are not damaged in any way. Enter diagnostics and make sure the following MIN NVM locations are correct: Location 152, Value 60, and Location 153, Value 85.

Everyone you talk to seems to have a solution or a super fix for this phenomenon and maybe they are all correct in his or her logic but as you will discover, there is a high price to be paid for the free advice. Before we consult any Docutech expert on the PO6-250/251 system fault shutdown we may want to do a few tests first. Start off with the following: ROS Patch Exposure Adjustment in DC-951. Consult the Adjustment section of the service manual for this procedure before you do it. If the RAP and the above information do not resolve your PO6- Output Imaging problem, then electrical ‘Noise’ may be causing the ROS faults. Consult the SCP Printer Fault History; if you notice any PO3-xxx faults are occurring at the same time stamp as the PO6—ROS faults, go to the electrical Noise Procedure in the service manual (Section 1NRD).

ROS Video Driver PWB. A vendor problem was identified (in 1995) on the image data driver PWB. In this situation, the video delay modules on board can cause a scan line to be intermittently short and thereby not sensed by the scan detector boards. A number of these components are on board and are located at U9, U10, U12, and U13. (These boards may have been used in ROS’ manufactured between June 1994 and January 1995. The vendor has corrected the problem and the new improved video driver board has been cut in: New ROS serial number #11258, remanufactured after January 25, 1995. NOTE: If any of the delay modules are labeled with a 4 –digit number from 9428 to 9450, they are suspect to cause this problem. If the letter “S” is followed by the serial number then the component has been screened and is not likely to be defective. NOTE: Whenever you replace an image data driver PWB, match the dipswitch configuration at U8 with the old board, if applicable.

Image Data Driver PWB: 140K47832

Repair kit: 600K28511 PWB and P-197 Label.

ROS Video Driver PWB

PO9-203/213 Faults with very ight images.
Cause: The process control has detected an extremely high dark decay value. No ROS faults were detected. This could be one of two situations:

Situation 1, the scan beam is constantly on. The developed images, including process control patches, appear as if they are very undertoned. Actually, every other scan line is white and the images exhibit a “corduroy” effect when viewed with a magnifier glass.

In Situation 2 the process control patches are not being created. The scan line does not turn off in the patch area. However other image areas appear normal when developed.

Solution:

Replace the Image Data Driver PWB.
Replace the Video Cables: From the Card Cage to the ROS.
Replace the Coax Cables: From the Image Data Driver PWB to the Modulator PWB.
Replace the Image Data Driver PWB and perform the PO6-701 RAP.
NOTE: When replacing the Image Data Driver PWB, match the dipswitch configuration at U8 with the old PWB, if applicable.
Requirements for field resolution:
Image Data Driver PWB: 140K47832
Repair Kit: PWB and P-197 label 600K28511.
117K7950 Video cables (2)
117K3071 Coax Cable channel 1
117K3081 Coax Cable channel 2

PO6-250/251/357 Intermittent.
Electrical noise in the IOT can generate PO6-xxx faults. Spikes on 115 VAC Phase A can cause an unfiltered ROS HVPS to operate erratically, resulting in various faults. If you see prints with a narrow black band or if they are half black and half white, the new power supply has a line filter installed on the AC input wiring.
Solution: Install the new style ROS HVPS. TAG P-269. Part number 105K10480.

Half White / Half Dark Print
Chain 6- printer (output) imaging:
If you notice half white / half dark intermittently (with or without PO6-250 / 251) system faults, the Modulator inside the ROS assembly may be defective. This modulator is not spared and you will have to replace the ROS assembly. Always keep in mind that the problem could be caused by noise. Look for a broken metering roll ground strap, bad dicorotron, bad metering roller, etc. The bearings inside the metering roller could cause a noise problem. Look at the following MIN location: 125— it should be at 80. MIN location 125 is fault masking. Install the new style ROS HVPS 105K10480 (with P-269).

PO6-357 at power up.
If you are experiencing PO6-357 at power up sequence, check the following MIN value. Look at the value in MIN 430 if it is 249 or 251, and use the PO6-351 RAP to troubleshoot. However if the MIN 430 is 253, use the PO6-352 RAP. For all other values in MIN 430, use PO6-357 RAP.

Noise Generators

As a technician that has run into a brick wall in troubleshooting a PO6-xxx problem, I have to consider noise contributing to the problem. It’s a little bit frustrating because noise is something we really can’t hear or see, but the Docutech is affected by it in a big way. Almost any electrical device can produce a noise that will have some sort of effect on the operation of the Docutech. I have compiled a list of a few documented examples that should be checked out.

(1) Fuser Metering Roller Ground Strap. The ground strap should be in contact with the metering roller bearing assembly and ground. If you remove the metering roller for closer examination, use your OHM meter to see what the resistance is between the bearing and the metering roller body. The resistance should be zero or close to it. If you notice high resistance between the metering roller and the bearing assembly, then it’s time to replace the metering roller.

(2) Bindexer Door Ground. Make sure the Bindexer Door is properly grounded in the finisher. With the door un-grounded there will be a lot of noise generated, as paper is stacked in the Bindexer assembly.

(3) Printer Left Rear Panel. Don’t ask me why this could be a problem but I have noticed that if the panel is not grounded properly, noise will be generated and then weird stuff will happen. (Do you like that technical talk?)

(4) Top Transport Idler Shafts Grounding Tabs: PL3-F5, item 10, and 115E861 idler ground strap and nip shaft assemblies.

(5) Paper Tray elevator motors and the windings in them.

(6) Paper tray interlock switches and the wiring.

(7) Cleaner assembly arcing internally.

(8) Cleaner assembly housing Vacuum Duct, grounded rib arcing.

(9) K403 relay at cycle up or cycle down.

(10) K105 relay, severely burnt contacts on phase ‘A’.

(11) Active Heat Vent, poor connection at rear panel.

(12) Check and examine all male and female pins on the lower AC panel in back of the Docutech. Check all the pins in the LVPS as well. Make sure that all pins are free from fretting, corrosion, and foreign contamination or just plain dirty. Replace all male and female connectors and pins with the new gold plated pin kit.

Next month we will examine Measuring Raw Output Power of Helium – Neon Laser Tube and The ROS Patch Exposure Routine. Something that I am sure will really excite you or maybe put you to sleep. Meanwhile if you have any thoughts on problems you have had in troubleshooting or repairing any PO6-xxx system faults, please feel free to submit your ideas. I can be reached at: VillageCopierNY@AOL.COM.