Docutech NP-135 printer Ros system faults

By Raymond Cote

Probably one of the most disturbing fault codes you will ever encounter on a Xerox Docutech Printer is the fault code PO6-250 / 251. This fault code indicates that there was at least one end of scan that was not detected by the End of Scan PWB.  Take note of the initial actions before you jump into the Repair Analysis Procedure (RAP). Check all communication lines (video and bus) for proper connections and insure they are not damaged in any way. It might be useful to use Deoxit on the connectors if they appear to be contaminated in any way. Before you start troubleshooting this fault code check the following MIN Locations: 152 value should be 60, and MIN Location 153 should be 85. With these MIN values set properly we can start to troubleshoot this system fault. Keep in mind that if the RAP does not fix the system fault (and it usually doesn’t) then you can assume there is an electrical noise causing the problem. PO6-250 / 251 are, in my opinion, disturbing because, in most cases, electrical noise was the cause. Take a close look at the SCP Printer fault History were there any PO9-xxx or PO3-xxx system faults that occurred at the same time as the PO6- ROS faults?

     After replacing all the dicorotrons and reseating all the communication lines and you still have the ROS faults you are back to square one.   That’s when you should consider going back to basics and use the NRD2 Electrical Noise procedure RAP in the service manual. Look in the section 1NRD for additional information.

     Like most technicians when we dive into the rap we usually end up replacing whatever component that the rap recommends. We change the parts and that seems to fix the problem, then a day or two later the original problem returns. If you have an unlimited budget you will eventually replace most, if not all, of the PWB’s in the circuit, the polygon motor or the whole ROS assembly without success.

     The first time I ever saw this system fault I was at an account that had three Docutechs in the same room. In a way it was a blessing because I was able to swap parts till the problem went away. The problem never “went away” even after swapping all the components in the RAP for PO6-250 / 251. That includes the ROS assembly as well. When you run out of things to change and you run out of patience the technician in you starts to examine (seemingly) almost anything.  The first Docutech NP-135 printer that displayed this problem was caused by a faulty Plug / Jack connector to the Fuser Drive motor (MOT 402) 127K9360 (PL1-G11). I had swapped almost every component in the Docutech printer and almost 30 hours later found that the problem was a few (really) burned and pitted pins in the connectors (P/J264 and P/J 273 figure 6 in the wiring data) to the MOT 402.  One connector was so badly damaged from arcing it had to be replaced along with most of the pins. One of the P/J connectors was responsible for that electrical noise and once it was fixed the problem was resolved.

     Almost two years later I ran into a similar situation and instantly went for the connectors I mentioned before. The fuser developer drive motor (MOT 402) connectors were in fine shape and didn’t appear to be causing the problem. The fault code PO6-250 / 251 was persistent and would not go away. The RAP led me nowhere and I was at square 1 once again. The electrical noise could be from almost anywhere and I started to examine all the connectors in the processor, especially the connectors that were close to the ROS assembly. This time the probable cause was the High Voltage connector to the HVAC Power supply. It appeared to be somewhat pitted and discolored from arcing. There were a few 09-xxx system faults but none of them were at the same time stamp as the PO6-xxx faults. On close examination to the Plug 289 / Jack 5, I noticed two pins badly pitted and burned. When the pins were replaced that resolved the PO6-xxx problems.

     At team meetings fellow tech reps reported problems with many other Plug / Jacks in the processor that caused the PO6-xxx system faults. When examining P/J Connectors near the MIM Compressor Motor make sure the power is off and the main power cord is unplugged (for safety). Check the following Plugs and Jacks for burned or pitted pins: P218, P272 / J1, P209, P/J 292, P10 / J2, P270 / P1, and P/J 256. Check figures 9 MIM Right Rear Wiring Data for Plug Jack locations.

     Another team meeting exposed bad HVDC PWB’s and HVAC PWB’s that caused the system fault code PO6-250 / 251. In my career with Xerox I only saw this one time. For the most part, all Power Boards used on the Docutech are extremely reliable. The HVAC and HVDC PWB’s that did fail were directly related to a pin that was damaged from vibration and had pitted, this caused a noise which triggered the above system fault.

     Personally my favorite is the AC Distribution Panel located on the rear of the processor. The AC distribution panel is usually responsible for a wide host of faults both intermittent and hard failures.  There are always a few pins that are damaged from the vibration on that panel. Check the wiring data figure 20 in the manual for the location of the following components: P269 / J1, J285 / P1, and on the left side of the AC distribution panel J4211 / P3, and P2 / J377. Replace all the pins that show any sign of arcing or pitting. When repairs are complete use two (2) 6” ty-wraps to secure the Plug Jacks from vibration.  Incidentally, this information is also applicable to the entire 5090 family as well.  It could be the root cause of almost any intermittent system fault in the 5090 and Docutech family. 

     A fellow technician from the mid west submitted a fix for a message on the Docutech printer that would not clear. The message was: “Touch screen has been disabled”. The most logical approach is to clean the bezel on the touch screen. When this doesn’t work try removing the bezel and cleaning it the old fashioned way.   Always power off to access the bezel. On the Docutech. Lower the front of the UI bezel. Slide the bezel to the left to get it off the hinges. Locate the four 5.5mm screws in the far corners and remove the screws. Remove the four 7 mm screws that secure the hinges to the bezel on the rear of the bezel. Carefully lift the black plastic (protective) inner cover off the bezel; this will reveal the LED PWB and Phototransistor PWB’s. Clean all LED and Phototransistors with a soft cloth and film remover. Clean the translucent part of the bezel that the LEDs shine through. And then reassemble the unit.

     In real life, we don’t always have that luxury of swapping parts with another printer, nor do we have the unlimited budget to replace all the parts we think are bad. We actually have to fix the beast as quickly as possible with the smallest repair budget possible.

If you have information that you would like to share with the field, please feel free to submit your ideas to VillageCopierNY@aol.com and I will place your suggestion or fix in the next issue of ENX. From what I hear in the field, it seems that many ex-Xerox technicians miss the field engineering team in Rochester, N.Y. Somehow it was always reassuring to hear a voice on the other end of the phone and a field engineer making a suggestion for a fix on your problem