Solutions to PO6-250 / 251 System Faults

                                            By Raymond Cote

All too often I hear ongoing complaints from the field concerning PO6-250 / 251 system faults and the agony to resolve this issue. From my own experience there are two types of PO6-250 / 251 system faults that you will encounter in the field: one is the hard failure and the most common one is the intermittent fault. The hard failure is almost always solved with the RAP’s but the intermittent problem can, in some instances, take several days to resolve.  It may seem like this system failure is the hardest one to resolve and let me tell you it sure is. Many techs, and customers alike, have complained that they have done so many things to resolve the issue that they have forgotten what it was exactly that they did that resolved the issue. And in some situations the problem refuses to go away and they just deal with it. From my experience with this product, there are a number of components that can attribute to this system fault and in some situations it could be caused by more than one component.  My first suggestion is to go to the PO6-250 / 251 RAP in the field service manual and start with the Initial Actions, and make sure that the MIN NVM locations have the correct values:

Once you start the RAP continue with it to its conclusion. If the Rap does not resolve the issue of PO6-250 /251, then try the following home remedies. I would like to thank all the service techs and customers that have sent in their comments and repair tips on what to look for and what they found that fixed this problem.  Every time I go through this Rap, I discover something that I May have overlooked the previous time and it’s almost like I am learning something new all the time. In my experience, the first few times I went through this RAP it was strictly by the book, but as time went on I was gaining a deeper knowledge in the imaging process. Don’t limit yourself to just the RAP on this system fault.  Open the Wiring data (section 7) and follow along with the BSD’s to see where the signals are coming from and where they are going.  As you become more aware of how the Output Imaging works in this family of printers you will become more comfortable and confident in the troubleshooting of this phenomenon, and in effect you are learning something new all the time. It was and still is my experience that when the PO6-250 / 251 system fault is a hard fault, it was easier to troubleshoot and repair.  But in most cases the fault could be an intermittent problem that shows up to annoy and pester the customer at the worst possible times during a job. 

The ROS Assembly is, for the most part, very dependable and requires very little maintenance.  Once a year, as a precaution, you may want to remove the ROS from the printer and clean all the mirrors inside with a soft “Q” tip device.  In several instances dusty lenses and mirrors inside the ROS was causing PO6-250 / 251 system faults. After cleaning the components and re-assembling the ROS it worked fine.  The polygon motor has a few mirrors inside that may have some dust on it and a clean “Q” tip used on these mirrors will eliminate future problems.  Make sure that when you re-install the ROS assembly, it is seated (exactly) in the same position it came out of.  There are two bayonet pins, one on either side of the ROS that have to travel in a guide. When the ROS is seated tighten up the two 10 mm nuts and re-connect all plugs / jacks, communication cables and the laser tube connection. 

A hard failure is usually easy to troubleshoot and repair, but in the scheme of tricky system faults, the intermittent ones are the most challenging to resolve.  In most intermittent situations an electrical noise is usually the culprit, and that “noise” can come from almost anywhere in the machine.

With the power off and the printer unplugged, remove the rear panel and drop the AC Distribution panel (PL5-A11) in the back of the printer. Get comfortable on the floor because you will be checking all the Plugs and jacks on the AC Distribution panel. To the right of K402, (Main Drive Run Relay) you will notice P269 and J1. Cut the ty-wrap (if it has one) and disconnect the P/J connector assembly.  Check all the pins in both halves and use the gold plated pins that are supplied in the 605K11850 “Connector Reliability Up-Grade Kit”. Replace any pins that are damaged, burned, pitted, or rusted.  When the P269 / J1 is repaired check J285 / P1 that is located to the left, and replace all the pins that need attention and then re-assemble both P/J’s and ty-wrap them in position. Vibrations from a running machine will cause fretting of the pins and ty-wraping the housing together will sometimes reduce the vibrations that cause the fretting. Almost always you will find one or two pins completely destroyed and if you check the wires to see where they came from and where they are going, you will discover that they are in the interlock circuit.  Could an intermittent interlock cause PO3-xxx system faults? You betcha! When you loose the +24 volt dc line all kinds of weird stuff happens even PO6-250 / 251 magic.  While you are on the floor, disconnect the other two P/J’s on the left side of the AC Distribution Panel Assembly.  J4211 and Plug 3 and P2 /J377. In most instances they were found to be in pretty good order. Once in a while they show signs of fretting due to a loose connection or machine vibrations. Repair or replace any burned pins and ty-wrap the PJ’s.  Also while you are down there, replace the ROS Power Relay K 109, part number 109P662 with a factory fresh (new) relay (PL5-A11).  K102 Interlock Relay and K403 Main Drive Relay 109P397 should also be replaced at this time.  Re-assemble the printer, power up the system and test it by running a few jobs.

Once the AC Distribution Panel has been attended to the next area of concern could be anyone’s guess. That’s what makes this job so interesting. Another area of concern is the Developer drive motor. Open the top left hand cover of the processor to expose the developer fuser drive motor assembly. Take a close look at the two P273/J273 and P264/J264 on top of the motor assembly. In several instances they have been noted for generating an electrical noise that will affect the ROS assembly. Examine both P/J’s and replace any burned, pitted, or damaged pins with the gold plated ones from the kit.  When the repair is completed use ty-wraps to secure the connectors.  While you are in this area, check all the connectors that you see and replace any pins that need to be replaced.       

The next area of concern that should be examined is the Dicorotrons assemblies. If you are getting PO9-201’s at the same time stamp as the PO6-250 / 251 replace all the housings. Sometimes the PO9-201’s do not get recorded in the shutdown log and it is my opinion that they should be replaced because they may have been damaged over time with wet rags that are used to clean the housings. Arcing from the Dicorotrons will cause a noise and the result will be a PO6-250 /251 system fault shutdown.  Order (5) Dicorotron assemblies (new) 125K1081 and one 125K1450. Make sure the new shields are being used in all positions. Remove, clean, and examine all Dicorotrons Connectors (PL4-B5). If you see any signs of arcing, or discoloration replace the Connectors. Check out the High Voltage Cable (PL4-B5) part number 117K6370 for signs of discoloration, or damage to the protective wire cover. If you even think the HV Cable is damaged replace it with a new one. Why take a chance with a used one?  Pitting and discoloration is a sign of arcing which will generate an electrical noise.  By the way, while the rear panels are off  take a good hard look at the HVAC  Output Module (PL5-B1) 105K1382 for signs of arcing at the connector or the P/J assembly. This could be a source of noise that will give you some grief. It’s difficult to see the white connector unless we remove the HVAC Output Module from the machine. If you notice any discoloration or arcing inside the connector then it’s time to replace it. Cleaning the contact will buy you enough time to get out the door, but for long term fixes the connector should be replaced.  

Last but not least is the Low Voltage Power Supply (PL5-B5) 600K13535. Shut down the printer and un-plug the power cord. Remove the LVPS from the machine and open the rear cover to expose the two DC relays.  K103, 34 Volt dc interlock relay and K104, 24 volt dc interlock relay (part number 109P397) should always be replaced with two store bought, brand spanking new relays only. For some unknown reason when you examine the old relays you will never find anything wrong with them (visibly and electrically) but the fact remains they do not work in the LVPS.  I can’t tell you the number of times I have used a little scotch brite to polish the contacts and re-install the same relays in the LVPS only to find that the problem still is with us.  What makes it so frustrating is the fact that the (used) relays check out electrically and appear to be in good condition and the intermittent  PO6-250 / 251 still remains with us.

If you have any information about PO6-250 / 251 system faults and you would like to share it with the field,  please do not hesitate to contact me with the information and I will gladly pass it along to the field. I can be reached at: VillageCopierNY@AOL.COM u by Raymond Cote