ROS CHECK OUT -  SET UP PROCEDURE

FOR DOCUTECH FAMILY OF LASER PRINTERS

 

By Raymond Cote

One of the most mysterious devices in the Docutech family of laser printers is the ROS Assembly.  It’s almost like a mental block with many techs because of the lack of information available to the field, and the fear that this device is something we know little about. In a way I can sympathize with technicians in the field as we sort of shy away from the ROS Assembly.  We go through the Raps, and try one fix after another, with the hope it will resolve the ROS’ faults.  In many instances the ROS Assembly is not the root cause of the PO6- 250 /251 system’s faults, and ultimately it’s due to noise that is generated in some other component or device in the machine. When I worked for the manufacturer it was easy to order all the components in the RAP, and replace them one at a time until the problem was resolved. I think it would be safe to say that most of us independents do not have that luxury and actually have to fix the device at an economical price.  If you determine the ROS is defective and beyond the repair of this check out procedure, you can order kit number 604K24800 through Xerox for $ 3,605.00.

Use this procedure for random PO6-250 / 251 and other ROS related faults. The Raps should always be used as a first step for all ROS related system faults. However, when an ROS related system fault cannot be resolved, this baseline adjustment will restore the ROS to factory specifications. 

CAUTION!

Power off the Docutech printer when working on the ROS assembly. The High Voltage Power Supply will deliver 2,400 volts DC., more than enough to curl your toes.

BEFORE YOU START THIS PROCEDURE!

     Check all six (6) black Molex connectors on the ROS assembly. The Black AMP connectors may have loosened up due to machine vibration, and might not be properly seated. In several instances, un-plugging the connectors and re-mating them sometimes help to improve the contact.

            J301 SOS PWB

            J302 EOS PWB

            P205 Distribution PWB

            P206 Distribution PWB

            P303 Modular DIP Switch Bank

            P304 Image Data Driver PWB

The ROS is extremely sensitive to electrical noise.  When you are troubleshooting intermittent ROS faults, be sure to rule out all high voltage arcing, especially in the Xerographic module. All motors and connectors in the photoreceptor belt cavity should also be closely examined for any signs of fretting or dissimilar metal corrosion.

Check K403 contacts on the AC panel (only if at cycle-up or cycle-down). This relay’s burned or pitted contacts have been known to generate an arc (electrical noise) when energizing.  The arc will induce an electrical noise directly into Phase “A” 115 VAC which is the supply for the ROS HVPS. Without a line filter, this arc will always cause the power supply to reduce its output momentarily and the laser tube assembly will “blink.”

• Check all the top transport idler grounding tabs.

• Tray ½ elevator motor wiring rubbing on frame

• Tray ½ interlock switch> CAN side intermittent.

• P256 on Photoreceptor Drawer: Loose connection Phase “A” to ROS.

• Cleaner Assembly internally binding / arcing.

• Cleaner Housing Vacuum Duct to Toner Filter (grounding rib arcing).

• Severely worn Developer Roll Bearings.

• K105: Burnt contacts arcing on Phase “A.”

• Heat Vent Installed?  Check the electrical connector at rear panel.

(A)  Check all Dicorotrons (PL4-B9), connectors (PL4-B3) and shields. Look for fretting, discoloration and any abnormal conditions of the components. Repair or replace as necessary.

(B)  Check all ground straps (PL3-D7) in the fuser area. Make sure the metering roller bearing is in contact with the metering roller ground strap.  Remove the metering roller and check the bearings on both ends to see if they are binding up.  Check the resistance with your Ohmmeter. It should be lower than 25 Ohms between the roller (surface) and the bearing assembly.

(C)  The Fuser / Developer drive motor (PL1-G11) has been known to generate electrical noise as well. In DC-330, main drive, check for any unusual noise coming from the Fuser / Developer Drive motor.

(D)  The pins in the connectors that live on top of the Fuser / Developer dive motor are also known to generate electrical noise when they become burned and pitted. The burning and pitting is contributed to machine vibrations.

(E)  Check the ground strap on the Bindexer door in the finisher (PL7-D9) item 27.

(F)  Try swapping the EOS and SOS PWBs (PL4-G3) to see if the problem code changes. If it does change to another system fault, it could be a bad PWB.

(G)  As a last resort before doing the ROS baseline adjustment, do the 1NRD electrical noise procedure. More times than often this procedure will resolve the intermittent PO6- 250 / 251 and related ROS system faults.  

NOTE!

All ROS units that were manufactured from December 1991 to November 1992 might have a defective shutter ribbon cable. Look for the date the ROS was manufactured. It’s stamped between the EOS and SOS PWBs on top of the ROS assembly.  When the ROS is on the workbench remove all seven, 7 mm screws to open the ROS assembly for inspection. Check the Liquid Crystal Shutter Ribbon Cable to see if it’s installed and connected properly.  To remove the ROS assembly, refer to PL6-B2, and the ROS cover removal PL6-B11 in the Service Data Fiche.

SET UP PROCEDURE!

The set up procedure should only be used when the problem cannot be resolved using the Rap’s 1NRD electrical noise procedure, or swapping the EOS with the SOS PWB.  Without the proper laboratory test tools, it’s almost impossible to measure the actual output from the laser tube.  However, the laser output is measured as it is seen by the SOS and EOS PWBs. The set up procedure is presented in four steps and once the procedure is started, all the steps should be completed, including the final adjustments.

LASER TUBE ALIGNMENT!

(1)  We will start with the laser tube alignment to insure the beam is straight. This can be done using an Allen wrench to adjust the maximum beam output.

(2)  The Shutter will be set to factory specifications and we will check that the EOS and SOS PWBs are both set to the same known value.

(3)  Check the laser tube and insure it is still providing maximum output.

(4)  Factory (standard) adjustments: When anything is changed in the ROS, all adjustments should be done before returning the printer to the customer.

Align The Laser Tube!

Turn the printer on and enter diagnostics. Remove the printer top cover and make sure all doors are closed. Use several sheets of 11 x 17 inch paper under the ROS assembly to protect the photoreceptor belt. Use a good quality voltmeter to check DC voltages. Connect one lead (-) to the connector on the laser tube that goes to ground, and the other lead (+) to TH 20 on the Distribution PWB (W TAG 198) (PL4-G3 item # 7a), or to pin 3, P302 on the EOS PWB (W/O TAG P-198).

Enter DC-330, select chain six (6) and then select Laser Write. Select start (right mouse button).  You will see three flags change state (on the screen) when you select start. Make a note of the voltage readings. 

Step One!

The next step is to physically move the laser tube (PL3-G3 item 5) to the best position. Insert the 3 MM Allen wrench to move the laser tube. The Allen head screw is located on the left side of the tube (when you are facing the rear of the ROS assembly with all the PWBs). The adjustment screw we are interested in is located on the mounting bracket that is close to the spring (PL4-G3 item 6) that holds the laser tube in place. Turn the Allen Head screw on the mounting bracket counter clockwise and then clockwise until the maximum voltage is obtained.  Compare this voltage reading with the original voltage reading.  It should be much higher.

Step Two!

Use “Power Off” in Diagnostics to power down the printer. Look at the switch matrix label on the cover of the image data driver PWB, (PL4-G3 item 9b) and copy the value of R36 on the label, we will need it for future reference. If the tag is not readable (which happens quite often due to the age of the matrix tags) then the ROS assembly has to be removed from the printer and the black cover.  It’s held on with seven, 7mm screws, and has to be removed to expose the shutter PWB (PL4-G5, item 5). Before the measurement is made the LCS ribbon cable has to be unplugged. Use a good quality meter to measure the resistance between TP1, and TP10 on the shutter PWB. The resistance should equal what was written on the Matrix Label. If not then adjust the value with the R36 (blue) potentiometer until the value is the same as the matrix. When the adjustment is made on R36, use a nonferrous screwdriver.  Plug the LCS ribbon cable back in after the adjustment procedure. While the cover is off, use a “Q” Tip to clean all mirrors and optic lenses. Replace the black cover(s) and reinstall the ROS assembly in the printer.

Step Three!

Power the printer “ON” (in diagnostics) and let the printer fully “Initialize” before proceeding. Make sure that you have 11 x 17 inch paper under the ROS assembly and then select DC-330, Chain 6, (and) Select “Laser Write” output, press “Start.” Use your DC voltmeter to measure the following voltages:  black lead (Ground) to the connector on the laser tube Ground (near the spring). And the positive lead to TH 20 on the Distribution PWB (With Tag P-198) if your printer is without Tag P-198 use Pin 3 of P302 (mounted on the EOS PWB) Record the value.  It should be about 1.4 to 1.6 Volts DC.  Use the potentiometer on the EOS PWB to adjust the value if necessary.

Caution !

DANGER WILL ROGERS !

Never remove any PWBs while power is applied to the printer. Never remove any PJ connectors while the power is on in the printer or major damage will occur. The potentiometer is accessible through a very unique (secret) access opening on the ROS Assembly.  To find this sneaky little access hole start by looking for the Distribution PWB (as a point of reference). On the Distribution PWB (upper left hand corner) P/J connector, just one inch to the left of this P/J connector, you will find a black plastic 10MM Hex Cap. This Hex Cap, when removed will allow access to the potentiometer. This black plastic Hex Cap is almost one inch below the EOS PWB.  While the power is on and you are in DC 330 with “Laser Write” on, use a nonferrous screwdriver to adjust the potentiometer clock wise to raise the voltage. Gently raise or lower the potentiometer until you obtain the correct voltage (1.4 to 1.6 Volts DC).

Laser Tube Output

Use this procedure to check it out!

(1)  Power off the printer (in diagnostics) and remove the ROS Assembly from the printer. Remove the cover assembly by removing the seven, 7mm screws (PL4-G5 item 4a). Un-plug the LCS ribbon cable at the Shutter PWB (PL4-G5 item 5).

(2)  Reinstall the ROS assembly (with the cover assembly off) and power on the printer.

(3)  Place a sheet of 11 x 17 inch paper on the photoreceptor belt under the ROS assembly to protect the belt.

(4)  Use your (DC) volt meter connected to the following test points:

• (-) black lead to the ground wire that is attached to the Laser tube assembly.

• (+) red lead to TP 20 (With Tag P-198). 

                        Or if you do not have Tag 198

• (+) red lead to Pin 3, P302 on the EOS PWB (W/O TAG P-198)

• Enter DC-330, Select [Chain 6], Select [Laser Write], Press “Start.”

• Record your voltage reading on a piece of paper.

• The voltage reading should be at least 10 VDC.  If it’s not then the laser tube may be defective and should be replaced. 

(5)  Power off the printer and remove the ROS assembly. Replace the LCS ribbon cable on the shutter PWB and reinstall the ROS cover assembly.  Remove the 11 x 17 inch paper from the photoreceptor.

(6)  Power up the printer in diagnostics and wait until the machine initializes. When ready, select DC-106 and verify that prints can be made.

Perform the following basic adjustments

Before returning the printer to the customer, please make sure that all the basic adjustments are within factory specifications.

A)        ROS Magnification Setup (Adjustment   6-D6)

B)        Side to Side (Slow Scan) Registration Setup (Adjustment 6-D9)

C)        Top to Bottom (Fast Scan) Registration Setup (Adjustment 6-D10)

D)        ROS Automatic Xerographic Setup (Adjustment 6-D12)

If you have information that you would like to add to this procedure please feel free to e-mail me at VillageCopierNY@AOL.COM and I will edit the information into the repair procedure for future reprints. All reprints of my articles are available to the field, so if you have missed something of interest to you please let me know what you need. u

Raymond Cote can be reached at Village Copier Service, 718-931-2830 • email: VillageCopierNY@aol.com