MAI COMPANY CONFIDENTIAL FIELD INFORMATION BULLETIN SERVICE GROUP(S): MICRO,MINI,LARGE MFG: OKIDATA NACS TYPE(S): N163 MFG. MODEL(S): 520,521 CATEGORY: PRINTER DESC: 9 WIRE MATRIX PRINTERS *** TABLE OF CONTENTS AS OF 09/23/96 *** FIB 00001.GENERAL.INFORMATION...............................(Text Inco12/22/95 FIB 00002.Printhead gap adjustment procedure..........................12/23/95 PRINTER-OKIDATA-520,521-----------------------------Table Of Contents Pg01 of 01 FIB 00002 MAI COMPANY CONFIDENTIAL 12/23/95 *** Printhead gap adjustment procedure *** Okidata ML520/521 & ML590/591 Printhead/Platen Gap Adjustment The ML52x & 59x family of Okidata printers do not have an operator adjustable forms thickness lever. These printers automatically sense forms thickness and adjust printhead distance from the platen to achieve ideal gap setting for best print quality. Automatic adjustment is possible only when Auto Gap is set under Gap Control in the Setup Menu for the Paper path being used (Rear, Bottom & Top Feed). Auto Gap is the default setting for each of the paper paths. Auto Gap automatically determines paper thickness once printing begins on the first page and will continue to recheck for each subsequent sheet fed. Semi Auto Gap performs the same operation but only for the first sheet. If a specific number is selected (1 thru 9), auto sensing is disabled and the specified number gap setting is continually used. Although these printers are capable of automatically adjusting the printhead gap, there is an initial reference gap that must be set and maintained. This manual check and adjustment is always required whenever the printhead, carriage assembly, space motor, gear case assembly or carriage shaft have been replaced or when attempting to resolve a print quality problem. Normal Operation When the printer is first powered On, or when the FF/LOAD button is first pressed, the carriage will move back and forth a few times and then stop at the far left side of the printer. This motion is not the printer attempting to sense forms thickness, but is used to reset the printhead to the maximum distance from the platen to allow the printer to load forms of an unknown thickness in front of the printhead without a paper jam. Remove the ribbon cartridge. View the top left side of the carriage assembly and verify the Gap Change Gear is set with range #9 displayed. Range #9 represents the greatest printhead/platen gap distance (approx .035"). Install single part continuous forms on the rear push tractors and press the FF/LOAD button. Forms will load in front of the printhead and the Gap Change Gear should still be set to #9. NOTE: With Auto Gap selected in the Setup menu for the paper path being used, the printer will not automatically adjust the Gap Change Gear from the initial power On paper load setting of #9 to the ideal Gap setting until some form of actual printing is accomplished. Reinstall the ribbon cartridge, enter Menu Mode and print the Setup Menu. When printing stops, remove the ribbon cartridge and check the Gap Change Gear setting. After printing on standard single part forms the range should have changed to #2. Very heavy single part forms or multi-part forms would cause the Gap Change gear to change anywhere from a range of #3 to #6. NOTE: Printer speed is also affected by forms thickness on these printers: Gap Setting 1~3 = 100% print speed, 4~6 = 80% and 7~9 = 50% print speed. Printhead and Platen Reference Gap PRINTER-OKIDATA-520,521-----------------------------FIB002 Pg001 The reference setting is .014" + .001" with the Gap Change Gear positioned to Range #2 (use a feeler gauge with no paper in front of printhead and no ribbon installed). Reference Gap Adjustment This procedure is also described and illustrated in Section 5 of the ML520 & 590 Maintenance Manuals, however there are additional comments listed here that should help clarify the procedure. 1) The adjustment should only be performed with the printer mechanism mounted on the lower cover (base) of the printer and the printer positioned on a level rigid surface. 2) Power Off the printer and move the Change Lever to the 'Rear' paper feed position. 3) Remove; paper, ribbon cartridge, printer upper cover, pull roller assembly and ribbon protector. 4) Ensure the two Phillips head screws securing the Space Motor Assy to the Carriage Frame are tight. 5) Ensure the Adjust Cam (white nylon lever) located above the right front foot. of the printer is positioned at the red mark set at the factory. 6) Set the Gap Change Gear (located on the left side of the carriage) to range #2 by turning the Adjust Screw (front of carriage) using a small Phillips Head screwdriver. To decrease the range turn the screw slowly counterclockwise while moving the carriage assembly to the left. To increase the range turn the screw slowly clockwise while moving the carriage assembly to the right. NOTE: Do not attempt to disengage the Adjust Gear (outer gear of the Adjust Screw) at this time. Also, the Adjust Screw is reverse threaded and excess clockwise turning may remove the Adjust Screw completely from the Space Motor PCBA. 7) Slide the carriage to the left side of the platen and check the printhead platen gap using a feeler gauge. The gap must measure .014" + .001" between the platen and the printhead wires with the Gap Change Gear positioned at range #2. 8) If the gap is out of tolerance, take a large straightened paper clip to push down on the Adjust Gear to disengage it. The Adjust Gear is the spring loaded gear ring on the outside of the Adjust Screw (located on the front of carriage). NOTE: Care must be taken when pushing down on the Gear to avoid damaging the nylon teeth. 9) While pushing down on the Adjust Gear with the paper clip, place a Phillips Head screwdriver in the Adjust Screw and turn slowly clockwise to increase the printhead gap or counterclockwise to decrease the gap. Remove the screwdriver and paper clip and make sure the Adjust Gear (outer gear ring) has re-engaged with the center Adjust Screw and returned to its normal upward position. 10) Check the gap again with a gauge. If out of tolerance repeat step 9. If within tolerance, move the the carriage to the far right side of the platen PRINTER-OKIDATA-520,521-----------------------------FIB002 Pg002 and test for the same gap setting. If the gap is out of tolerance, move the Adjust Cam clockwise to increase gap or counterclockwise to decrease it. 11) When the left and right gap are within tolerance, move the carriage to the middle of the platen and check the gap. When all 3 platen positions are within tolerance, no further adjustment is required. NOTE: Adjusting the Adjust Cam (white lever) will affect the gap with the carriage on the far right side of the platen, but will have little or no affect with the carriage on the far left side. ORIGINATOR: Mike Ramunni PRINTER-OKIDATA-520,521-----------------------------FIB002 Pg003