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Samtron SC-726GXL Service Manual

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COLOR MONITOR

SC-726GXL
1. Precautions
2. Reference Information
3. Product Specifications
4. User Controls
5. Disassembly & Reassembly
6. Alignments & Adjustments
7. Troubleshooting
8. Exploded View & Parts List
9. Servicing Diagrams
9-l. Block Diagram
9-2. Wiring Diagram
9-3. PCB Layout and Electrical Parts List
9-4. Schematic Diagram

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Summary of Contents for Samtron SC-726GXL

  • Page 1: Color Monitor

    COLOR MONITOR SC-726GXL 1. Precautions 2. Reference Information 3. Product Specifications 4. User Controls 5. Disassembly & Reassembly 6. Alignments & Adjustments 7. Troubleshooting 8. Exploded View & Parts List 9. Servicing Diagrams 9-l. Block Diagram 9-2. Wiring Diagram 9-3. PCB Layout and Electrical Parts List...
  • Page 2 It is essential that service technicians have an compartment cover or shields, isolation accurate high voltage meter available at all resistor-capacitor networks, mechanical times. Check the calibration of this meter insulators, etc. periodically. SC-726GXL...
  • Page 3 AC voltage drop across the resistor. Any reading of 5.25 Volt RMS (this corresponds to 3.5 milliampere AC) or more is excessive and indicates a potential shock hazard. Correct the shock hazard before returning the monitor to the user. SC-726GXL...

  • Page 4: General Servicing Precautions

    AC plug and accessible conductive parts (see above) should be greater than 1 megohm. Never defeat any of the B+ voltage interlocks. Do not apply AC power to the unit (or any of its assemblies) unless all solid-state heat sinks are correctly installed. SC-726GXL...
  • Page 5 1 Precautions l-3 Electrostatically Sensitive Devices (ESD) Precautions Some semiconductor (solid state) devices can be easily damaged by static electricity. Such components commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated circuits and some field-effect transistors. The following techniques will reduce the incidence of component damage caused by static electricity.

  • Page 6: Reference Information

    Separate Separate Separate Separate Separate Separate Remark Separate Sync A : Line time total 0 : Frame time total P : Sync width C : Back porch Q : Back porch E : Front porch S : Front porch SC-726GXL...
  • Page 7 2 Reference Information Chart Continued Table 2-l. Timi Apple Mac. VESA SIGMA Mode Timing 1280x1024 800x600 832x624 1152x870 1152x900 79.976 49.726 68.681 71.713 76.923 12.504 13.000 20.110 14.560 13.945 A usec 1.067 1.117 1.280 1.100 0.909 B psec 1.837 1.400 3.910 1.440 1.970...

  • Page 8: Semiconductor Lead Identification

    2 Reference Information 2-2 Semiconductor lead Identification DG3, DG4, DG5, DG6, DG7, DAl,...
  • Page 9 2 Reference Information 2-2 Semiconductor Lead Identification SC-726GXL...

  • Page 10: Product Specifications

    Storage Temperature : -4°F to 113°F (-20” c to 45” C) Humidity : 5 % to 95 % 897 25013OAA (Hitachi) : ASC Coating CRT Code No. SC-726GXL complies with SWEDAC (MPRII) recommendations for reduced electrostatic fields. Designs and specifications are subject to change without prior notice.
  • Page 11 3 Product Specifications 3-2 Dimensions 428 mm 428 mm 439 mm Swivel angle SC-726GXL...

  • Page 12: Pin Assignments

    Composite sync can be applied separately, or combined with the Green video signal (commonly referred to as “composite sync-on-green”). If composite sync-on-green is used, then only 3 of the 5 BNC connectors are used. The connectors are Figure 3-3. BNC Signal Input Type labeled accordingly. SC-726GXL...

  • Page 13: User Controls

    4 User Controls 4-l Front View and Cotitrols 4-l-2 SC-726GXL Front Control Panel 4-l-l SC-726GXL Front View Description Symbol Power Button (Push) Power Indicator LED (Dual Color1 Contrast Control Brightness Control Adjustment Controls Degauss Button Push once: Recall Push twice: BNC/D-SUB...
  • Page 14 4 User Controls This monitor requires a cable adapter for Note I: use with a R/iacintosh computer. The MacMaster Cable Adapter supports all monitors an?I all Macintosh, Centris, Quadra, Duo Dock, and Power Macintosh computers. If you do not already have a dealer.

  • Page 15: Disassembly And Reassembly

    5 Disassembly and Reassembly This section of the service manual describes the disassembly and reassembly procedures for SC-726GXL monitor. WARNING: This monitor contains electrostatically sensitive devices. Use caution when handling any components. 5-l Disassembly 5-l-l Removing the Cabinet With a pad underneath it, stand the monitor on its front with the screen facing downward and the base closest to you.
  • Page 16 5 Disassembly and Reassembly in the PCB Bracket, remove the power shaft and 5-l-3 Removing the Main PCB lift the Main PCB out. If you have not already done so, remove the Set main PCB on a smooth, level surface which Video PCB.

  • Page 17: Replacing The Main Pcb

    5 Disassembly and Reassembly 5-2 Reassembly With the CRT facing downw-ard on a protective pad, use the steps that follow to reassemble the monitor. 3. ‘Replace the CRT PCB 5-Z-l Replacing the CRT 4. Position the Main PCB Ass’y on the front cover With the front cover assembly lying face down (see figure 5-5) and hold it secure with two on a protective pad, position the CRT so that the...

  • Page 18: Alignments And Adjustments

    Adjust VR601 to DC 1 95 V+l V at Q406 heat sink Center Raster and GND. Adjust SW401 so that the back raster comes to the center when you apply a signal of 60 kHz/75 Hz. 6 - l SC-726GXL...
  • Page 19 6 Alignments and Adjustments 6-3 Using the Microcomputer Control Jig Table 6-l. Micom Control Jig Function Keys LCD PANEL _ General Control Color Control Key Function Key Fllnction Horizontal Position Right R-Gain Increase Horizontal P&ion Left R-Gain Decrease Parallelogram Right ACL Increase Parallelogram Left ACL Decrease...

  • Page 20: Horizontal Size Adjustment

    6-3-2 Color Control 6-3-l General Control Use general control to test and adjust the shape color control to test and adjust the color and size of the display. coordinates the monitor displays. 1. Simultaneously press buttons 28 and 23 to Simultaneously press buttons 28 and 23 to toggle between General Control and Color toggle between General Control and Color...
  • Page 21 79.976 kHz/75 Hz Factory Preset Timing Modes Difference Standard Mode Each block (5%) adjacent blocks (4%) 18.2 - 20.1 Vertical Less than 0.8 Horizontal 17.1 - 18.9 Horizontal: Less than 0.7 m m : 18.2 - 20.1 Vertical Less than 0.8 SC-726GXL...
  • Page 22 To delete the picture data from user’s modes, press the degaussing button for 5 or more seconds. 6-4-13 Save the Data With microcomput$r control jig: To save the picture data for a mode, push the mode save button (5). Figure 6-5. Pinchshion SC-726GXL...

  • Page 23: Color Adjustments

    6 Alignments and Adjustments 6-5 Color Adjustments 6-5-3 Color Adjustments for 9300°K color adjustmentsyoumusthave make one of the following configurations: 6-5-3 (a) Adjustment of the Back Raster Color Micom Control Jig and Signal Generator. (60 kHz/75 Hz, Back raster pattern) 1.
  • Page 24 Display a full white pattern. If the white balance differs from the above Turn the contrast and the brightness controls fully clockwise. When correct, press buttons 5 to save. Using buttons and 12 set the R/B gain data td x=0.313&.02, y=O.329&.02. SC-726GXL...

  • Page 25: Focus Adjustment

    6 Alignmenmts and Adjustments 6-5-4 (e) ACL Point Adjustment Refer to the procedure for 9300°K on page 6-7. Refer to the procedure for 9300°K on page 6-7. 6-6 Focus Adjustment Adjust the focus control of the FBT to display Display the H character pattern so that the the sharpest image possible.

  • Page 26: Convergence Adjustments

    These Unlock the rings and rotate the individual wedges were installed by the CRT rings (change the spacing between tabs) to converge the vertical red and blue lines. for this CRT. Removal may result in damage to the CRT. SC-726GXL...
  • Page 27 6 Alignments and Adiustments - - - Figure 6-10. Magnet Configuration Red and Blue Alignment Red, Blue and Green Alignment Crosshatch Pattern Figure 6-l 1. Magnet Movements 6-10...
  • Page 28 Display Image: Crosshatch pattern mixed with RGB colors. Bow convergence adjustments are not available for any of the CRTs used in the SC-726GXL. While all the CRTs have bow convergence magnets, they are Figure 6-14. Horizontal Line Balance Misconvergence sealed in the CRT factory and are not user or service technician adjustable.

  • Page 29: Troubleshooting

    7 Troubleshooting Notes: 1, If picture does not appear, fully rotate the brightness and contrast controls clockwise before inspection. *High voltage develops but no raster appears: Video output circuits. *High voltage does not develop: Horizontal output circuits. Horizontal line on raster Check the power supply circuits.
  • Page 30 7 Troubleshooting Check the horizontal drive Does drive pulse appear circuits. (IC401) Does drive pulse appear Check the push-pull circuits. at emitter of Q402? Replace Cl401 or check its Does drive output pulse related circuits. (D407, 0408, appear at drain D409 and T401) of Q401? Check flyback pulse at collector...
  • Page 31 Power indicator is green. Does the pulse appear at Check C&02. Q503 and Q505. Power indicator is orange. Check signal cable connection Does H/V sync output Check MICCIM (IC201). appear at pins 26 and 30 of ICZOl? Check IC401. SC-726GXL...
  • Page 32 7 Troubleshootino No Video Power indicator is green. Does DC 12V appear at Check DC 1% line pin 11 of IC104 or Pin 6 of IC601. Pin 8 of CNlOZ? Check signal cable Does the video pulse signal source, IC102 appear at pins 4,6 and 9 and IC109.
  • Page 33 Does DC 5V appear at Does the OSD video pin 9 of IC105 or signal appear at pins Pin 7 of CN102? Y e s Check IC105. Check DC t5V line on IC601 and the related circuit. Check Ql14, Q115, Q116. SC-726GXL...
  • Page 34 7 Troubleshooting No specific color appears The raster color is light green Note: Removing the signal cable displays a self raster screen. This screen displays the message “check signal cable” along with red, g:een and blue boxes. Use these boxes to check whether each individual color (R, G, B) is operating or not.
  • Page 35 Mode Active Green Active Normal Active Blanked Orange Active Inactive Stand-By Orange/Green blanking Blanked Active Inactive Suspend Orange blanking Blanked Inactive inactive Note: If signal cable is removed, DPMS function does not operate and a self raster is displayed. SC-726GXL...
  • Page 36 oes DC level change at p Check the buttons 18 and 19 of IC201 when you ush the front panel butto Table 9-I. Front Panel Button Location Function Pin 8alance Tilt C214 Vertical Linerity c215 C216 Horizontal Size Vertical Size c217 Horizontal Position C218...
  • Page 38 8 Exploded View and Parts List Memo...

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