This document describes the Wells-Gardner Electronics 19" In-Line Color Monitors, specifically models K4901, K4902, K4903, K4904, K4906, K4911, K4951, K4952, K4953, K4956, K4956R, and K4961. The manual provides service instructions, performance and operating data, a replacement parts list, oscilloscope waveform patterns, and typical DC voltages with input signals.
Function Description:
These monitors are designed to display color video signals, primarily for use in applications such as arcade games. They feature an in-line color picture tube, which is a common design for achieving color display. The monitors incorporate automatic degaussing coils (L701) that demagnetize the picture tube every time the monitor is turned on after being off for a minimum of 5 minutes, helping to maintain color purity. Some models are designed for vertical mounting of the picture tube, meaning the long dimension of the tube is oriented up and down, but electrically, there is no difference in how horizontal and vertical deflection circuits operate. The manual clarifies that "vertical" refers to the short dimension of the picture tube and "horizontal" refers to the long dimension.
Important Technical Specifications:
- Power Supply: The monitors operate within a voltage range of 108 VAC to 132 VAC and a frequency range of 50 Hz to 60 Hz. An isolation transformer with a minimum 1 Amp capability is required for servicing or testing to prevent shock hazards.
- High Voltage (EHT): For 19"V models, the high voltage is specified as 24.3 ± 0.8 K.V. at 0 Beam and 22.8 ± 0.8 K.V. at 1 mA Beam, under an A.C. input of 120V.
- Circuit Protection: A 4.0A pigtail fuse is mounted on the Main Board to protect the Power Output Circuit.
- X-Ray Radiation: The manual includes a warning regarding X-ray radiation, indicating that parts influencing X-ray radiation in horizontal deflection, high voltage circuits, and the picture tube are marked with a (+) in the parts list and must be replaced with the specified type.
- CRT: The monitors use a 19VLTP22 Pix Tube.
Usage Features:
The monitors are equipped with several controls for setup and adjustment, accessible on both the Main PC Board and the Neck PC Board.
- Main PC Board Controls:
- Vertical Hold Control (VR301)
- Vertical Size Control (VR303)
- Horizontal Hold Control (VR351)
- Vertical Raster Position Control (VR901)
- Horizontal Raster Position Adjustment Jumper (3 positions) - Note: Not provided on Model K4903.
- Screen Control (Part of H.V. Unit, T352)
- Focus Control (Part of H.V. Unit, T352)
- Horizontal Width Coil (L352, or L601 on Model K4904)
- Black Level Control (VR201)
- Horizontal Video Position Control (Horizontal Shift) (VR352)
- Vertical Damping Control (VR302)
- Neck PC Board Controls:
- Video Drive Controls (Red VR401, Green VR402)
- CRT Cut Off Controls (Red VR403, Green VR404, Blue VR405)
Maintenance Features:
The manual provides detailed instructions for various adjustments and service procedures:
- Power Up Warning: Emphasizes the use of an isolation transformer during servicing to prevent shock hazards due to direct connection of the chassis and heat sink to the AC line.
- Product Safety Notice: Highlights the importance of replacing safety-critical components only with manufacturer-recommended parts, identified by shading and (Δ) on the schematic diagram.
- Degaussing: Automatic degaussing occurs when the monitor is turned on after being off for at least 5 minutes. If the CRT shadow mask becomes excessively magnetized, a manual degaussing coil may be necessary.
- Color Purity Adjustment: This procedure involves adjusting purity magnets and yoke position to ensure uniform color display. It is recommended to perform this adjustment in the monitor's final location, facing west or east, after a 15-minute warm-up period. Steps include setting converger assembly, adjusting cut-off controls, pulling back the deflection yoke to see the green belt, adjusting horizontal width, moving purity magnets, and pushing the deflection yoke forward.
- Static Convergence Adjustment: Involves using 4-pole and 6-pole magnets to converge red, blue, and green beams in the center of the screen. A cross-hatch signal is required for this adjustment.
- Dynamic Convergence Adjustment: This precise adjustment uses rubber wedges to achieve the best circumference convergence at the edges of the screen. It involves tilting the deflection yoke and inserting three permanent rubber wedges, fixed with chloroprene rubber adhesive.
- White Balance Adjustment: This procedure ensures accurate gray and white brightness tracking. It requires an oscilloscope, digital multimeter, or VOM. Steps include grounding video inputs, setting drive and cut-off controls, connecting a measurement device to a video output transistor, adjusting black level, screen control, and remaining cut-off controls for best gray uniformity and neutral white.
- Parts List: Comprehensive lists of resistors, capacitors, semiconductors, transformers, coils, and miscellaneous parts are provided for the various models, with specific markings (shading or ★) for safety-critical components.
- Schematic Diagrams and PC Board Layouts: Detailed diagrams are included for different models (K4901, K4902, K4903, K4904, K4906, K4911, K4951, K4953, K4956, K4956R), showing component placement and circuit connections.
- Waveform Patterns and DC Voltages: Oscilloscope waveform patterns at various test points and typical DC voltages for transistors and ICs are provided to aid in troubleshooting and repair.
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