Contents Chapter 5.19 568X Ten Inch Sunlight Viewable Monochrome Monitor GENERAL DESCRIPTION INTRODUCTION The 10 inch sunlight viewable monochrome monitor operates as a VGA compatible video display in NCR 568X Automated Teller Machines (ATMs). The cathode ray tube (CRT) comprises a 10 inch tube with a yellow/green P43 phosphor and a clear glass screen. The monitor automatically senses positive and negative polarities of both horiontal and vertical sync pulses in order to display the following three modes or display formats: Mode Resolution Sync. Polarity Horiontal Vertical 1 640 (H) x 400 (V) Negative Positive 2 640 (H) x 350 (V) Positive Negative 3 640 (H) x 480 (V) Negative Negative The monitor operates at a horiontal line rate of 31.5 kh and a vertical rate of 60 H or 70 H depending on the mode chosen. It is powered from an external stabilied voltage source of +24 ± 0.2 Vdc and has a maximum current consumption of 1.5 A. The 24 Vdc source is supplied by the host terminal through a 2 pin Molex connector on the top of the monitor. Brightness Sensor A brightness sensor, implemented using a resistive photoconductive cell located in the facia of the terminal, automatically adjusts the brightness level of the display depending on the luminance level of the ambient light. The sensor is connected to the monitor via a 2-pin connector. 5.19-1
FUNCTIONAL DESCRIPTION The monitor comprises a metal enclosure containing the following components: 10 Inch CRT Video pre-amplifier board assembly Video amplifier board assembly (including brightness sensor) Scan board assembly, comprising: Horiontal deflection circuit Vertical deflection circuit Dynamic focus circuit. Refer to the diagram below and the schematic diagram on fold out FO-1, at the end of this chapter, while reading the following description. 5.19-2
- - - - 568X TEN INCH SUNLIGHT VIEWABLE MONOCHROME MONITOR 5.19-3
10 INCH CRT The monitor uses a 10 inch high brightness monochrome CRT which has a 28 mm neck diameter. Three voltages are required to give a sharp, focused pixel at the centre of the screen: An anode voltage (EHT) of 20 kv A focus voltage of 4 kv to 6.5 kv A screen grid voltage (G2) of 600 V to 650 V. The brightness of the CRT is controlled by applying a variable voltage at the screen grid, G1. A stabilied voltage of 6.3 Vrms at 230 ma, derived from the secondary winding of the line output transformer on the scan board, heats the cathode heating filament. The CRT cathode is driven from the video amplifier. VIDEO PRE-AMPLIFIER An analogue video signal of 0.7 Vp-p is applied through pin 2 of the 15 pin D- type connector to the inverter TR3. The signal input impedance is 75 ohms, given by R20, as the impedance of the inverter is about 10 kohms. The inverted signal is fed to pin 6 of the transistor array IC1, which has a high transition frequency (typically 550 MH). The gain of the amplifier is governed by the ratio of R15 and R16 to R31 at maximum contrast. Potentiometer VR1 controls the contrast and varies the emitter current of Q1. A low impedance output signal of 2.5 Vp-p (maximum contrast) is provided at pins 10 and 14 of IC1. TR3 and IC1 both invert the signal and as a result there is no overall signal inversion. A beam current limiter circuit provides protection for the CRT. A correction signal, BCL, formed at the cold side of the EHT winding (pin 7 of T2 on the scan board) and by the network of C33 and R29 (on the scan board) is applied to the base of the transistor TR2 where it is buffered and inverted. TR2 is biased at the base by R7 and R8, and at the emitter by R9 and R10, so that when the beam current exceeds 200 microamps, Ic through TR2 starts to reduce, its collector voltage increases and applies increasing current through R5 and therefore to pin 4 of IC1. This decreases the contrast level and therefore limits the beam current. A keyed horiontal clamping pulse is applied through TR5 to the video pre-amplifier clamping output transistor (TR4) for dc restoration of the IC1 output signal. The pre-amplified signal is fed to the video amplifier from the emitter of TR4, which provides a low output impedance. Series resistor R19 protects TR4 from any CRT arcing. Brightness Sensor The contrast of the display is automatically controlled by a photoconductive cell, PR1, connected between the base and ground of the buffer transistor TR1 on the video pre-amplifier. The cell is mounted on the brightness sensor board which is located in the facia of the terminal so that the cell is exposed to the ambient light. 5.19-4
The resistance change of PR1 is inversely proportional to the intensity of white light shining on it. Therefore, as the resistance decreases, the current through R4, and therefore to pin 4 of IC1 decreases and the contrast increases. The trimmer, VR1, on the brightness sensor is connected in parallel to PR1 to adjust the sensitivity level of the sensor. CAUTION The CRT and the brightness sensor are a matched pair and if either the CRT or the sensor fails then both components must be replaced. VIDEO AMPLIFIER At maximum contrast, and with a 0.7 Vp-p input signal, the video amplifier develops a maximum output swing of 70 Vp-p to drive the cathode of the CRT. The supply voltage of 105 Vdc is obtained by rectifying the positive horiontal flyback pulse from the line output transformer (LOPT), T2. Transistors TR5 (common emitter stage) and TR4 (common base stage) are connected to form a cascode circuit with relatively high input impedance, extended bandwidth and return isolation. The video signal is applied to the base of TR5 through resistor R21. A stable bias voltage of +5.1 V is applied to the base of TR2 through the diode D1. The overall gain of the amplifier is formed by the ratio of collector resistors R6 and R7 in parallel, and the resistor on the emitter of TR5 (R20). Series collector coil L1, and the emitter network, R19 and C9, form the peaking networks for improved bandwidth. The complementary output emitter followers, TR1 and TR3, reduce the effective load capacity across the load resistors R6 and R7, thereby extending the frequency response. D3 and D2 are the biasing diodes. R10 and R15 serve as current limiting resistors. The output signal directly drives the cathode (K) through the protection resistor R9. The Ekulit neon lamp, LA1, provides protection by conducting when there are any high voltage spikes caused by arcing. Horiontal and vertical blanking is applied to the video amplifier at the emitter of TR2 using an emitter follower circuit, TR4. R11 and R12 bias the base of TR4, and the bias formed by R17 and R18 makes TR4 conduct only during the horiontal and vertical blanking periods. The focus voltage, G4, of 600 V to 650 V is applied to the grid (G2) through the protection resistor R4. This voltage is derived from VG2 (approximately 840 V) and the resistor divider of R2 and R3. 5.19-5
SCAN BOARD Horiontal Deflection Circuit The four gate EX-OR chip, IC1, operates as a horiontal and vertical sync polarity sensor. The horiontal sync output from gate D (pin 11) remains positive when the horiontal sync input signal is either positive or negative. Similarly with the vertical sync output from gate A (pin 3). R4, C1 and R3, C2 form an integrating network with a long time constant compared to the horiontal and vertical sync polarity time period. The output levels of gates B and C (pins 4 and 10 respectively) change from low to high when the horiontal or vertical sync polarity is positive; with negative sync polarity the gate outputs are low. The main functions of IC2 are: Horiontal oscillator (pins 14 and 16, VR1 and C14). Sync separator (if composite sync is applied). Two phase loops (pin 1 and pin 2). Open collector drive pulse with constant duty cycle (pin 4). X-ray protection circuit for switching off the horiontal drive output. The first phase loop (pin 17) compares the phase of the incoming horiontal sync pulses and the oscillator. The free running frequency of the oscillator is set at 31.5 kh and is adjusted by VR1. The second phase loop (pins 2 and 3) compares the phase of the oscillator and the horiontal flyback pulse applied to pin 2 through R23 and R18. This loop compensates for storage time variations of the horiontal deflection transistor, TR3. VR2 adjusts the phase by injecting an additional current into the phase shifter (pin 3). IC2 contains an internal protection circuit which turns off the output drive if the voltage at pin 8 falls below 4 V or rises above 8 V. This provides over-voltage protection, and therefore X-ray protection, for the line output stage. A voltage proportional to the peak value of the line flyback pulse is applied to pin 8 of IC2 via the trimmer VR1 on the EHT filter board. The flyback voltage from the collector of TR3 is applied through R23 and rectified and filtered by D1 and C1 on the EHT filter board. The trimmer is set for exactly 7 Vdc at pin 8 of IC2 so that the voltage is below the upper trip threshold of the protection circuit under normal operating conditions. If the flyback peak voltage increases above the threshold, which means that the EHT exceeds 21.5 kv, the voltage at pin 8 operates a trigger circuit which inhibits the oscillator and turns the line output stage, and hence the generation of the EHT, off. The circuit continues to block the oscillator until the cause of the failure has been rectified, and can only be reset by completely switching off the monitor and switching on again. R19 is the collector resistor of the open collector transistor TR2. The horiontal output pulse from pin 4 drives the driver circuit which consists of the driver transformer T1 and the driver transistor TR2. The driver stage operates in the non-simultaneous mode; TR2 is off when TR3 is on. R22 and C19 added across the primary winding of T1 reduce the voltage peak on TR2. The flyback tuning capacitors, C22 and C23, and the horiontal deflection coil are connected directly across TR3. C22 and C23 give a nominal flyback time of 4 microseconds (measured at the ero crossing points). 5.19-6
Asymmetric scan linearity correction (the left edge with respect to the centre) is achieved with the horiontal linearity coil L2, and symmetric lineariation (both edges with respect to the centre) is obtained from the S- correction capacitor, C32. L1 adjusts the horiontal width of the raster and is connected in series with L2 and the horiontal deflection coil. The network formed by R24 and C21 in parallel with L1 and L2 acts as a damper to avoid ringing. D16 acts as a damper diode and is connected to the collector of TR3. To avoid ringing, booster capacitor C30 is connected to pin 4 of T2 through a snubber network of L5, C31 and R28. The supply voltage of +24 Vdc is connected to pin 10 of the LOPT (T2) through the diode D8 and the decoupling filter network of L4 and C24. T2 incorporates a three diode unit generating an EHT voltage of 20 kv with low internal impedance. Potentiometer VR11 (FOCUS) is mounted on the transformer. A bleeder resistor is incorporated at the output of T2 which acts as a pre-load on the EHT, and also discharges the CRT after switch off (for safety and to reduce spot burn-in). A high voltage C-Block capacitor, CE, on the EHT filter board is connected between the EHT lead and ground. The capacitor avoids any dynamic distortion of the display at high beam currents. Several auxiliary voltages are generated by rectifying the flyback pulses sourced from T2, these are: B+ -VG1 VG2. The CRT filament voltage of 6.3 Vrms is sourced from pin 1 of T2 and applied via R35. The brightness is adjusted using the G1 potential of the CRT. The brightness control is formed by the resistor and potentiometer network of R32, VR9, VR10 and R34 connected across B+ and -VG1. Filter capacitor C36 is also connected across B+ and -VG1 to avoid spot burn-in of the CRT. The horiontal flyback pulses from the collector of TR3 via C26, R26, C25 and D4, and the vertical flyback pulses from pin 13 of IC3, via R49 and D13, are summed to produce the horiontal and vertical blanking pulses. Diodes D3 and D5 limit the horiontal flyback pulses to 0 to 12 V. IC4 is a 12 V voltage stabilier which supplies 12 V to the video preamplifier, and IC2 and the driver transistor TR2 on the video amplifier. 5.19-7
Vertical Deflection Circuit The vertical deflection circuit generates a sawtooth or ramp current which is applied to the vertical yoke to produce vertical scanning in sync with the external sync pulses applied to the monitor. This is performed by IC3 which incorporates the following functions: Synchroniation circuit Precision oscillator and ramp generator Power output amplifier with high current capability Flyback generator Voltage regulator Precision blanking pulse generator Thermal shutdown protection CRT protection, which blanks the beam current in the event of loss of vertical deflection current. The vertical sync pulses are applied to pin 5 of IC3 from gate A of IC1, via the network formed by D2, R47, R46 and C42. The oscillator frequency is determined by the RC network of R58, VR8 and C48. The vertical hold potentiometer, VR8 (V.HOLD), adjusts the oscillator frequency. The supply voltage of +24 Vdc is applied to pin 14 through the filter network of R52, C44 and C45. C43 is the flyback capacitor which connects the output of the flyback generator (pin 15) to pin 2 which is the supply voltage of the power output stage. During trace time the supply voltage is obtained via D12, while during retrace time it is obtained from the flyback generator. The output of the power amplifier (pin 1) drives the vertical windings of the yoke. Pin 12 is the inverting input of the amplifier. The network R59 and R62 defines the dc level across C50 to allow the correct centring of the output voltage. The series network of R63 and C51 in conjunction with R62 and R59 applies a small part of the parabola available across C50, and the ac-feedback voltage taken across R64, to the feedback input of pin 12. For vertical shift, a dc current is injected at the cold side of the vertical coils. This is obtained by means of a resistor divider, VR3 (V.SHIFT), between the vertical supply voltage and ground. The linearity control, VR7 (V.LIN), is obtained by applying feedback between the output of the buffer stage, pin 10, and the tapping of capacitors C46 and C47. C47 is connected to pin 9 of IC3, which is the input to the buffer stage. Vertical height is adjusted by VR6 for mode 3 (60 H). The vertical height compensation for modes 1 and 2, VR5 and VR4 respectively, are switched on by output gates B and C of IC1. NOTE: VR6 must be adjusted before adjusting VR4 and VR5. Vertical blanking is obtained from the output of the vertical blanking generator, pin 13, and is summed with the horiontal blanking at the junction of D13 and D4 to produce the blanking signal. 5.19-8
Dynamic Focus Circuit The defocussing action of the deflection process and the difference between the path lengths of an axial electron beam and one which is deflected to a corner of the screen produces a change in focus requirements between the centre and edges of the CRT. This is compensated by a parabolic focus voltage waveform of approximately 350 V in the line direction and 100 V in the field direction. The focus voltage increases as the deflection angle increases. The line frequency parabolic waveform is obtained directly from the S- correction capacitor C39. The field frequency parabolic waveform is obtained by integrating and shaping the sawtooth voltage across the feedback resistor R64. The integrating circuit is composed of C38 and R40. The same amplifier circuit is used to amplify both waveforms to the correct level. Two series connected output transistors, TR4 and TR5, are used for the dynamic focus voltage requirements. The final dynamic correction waveform is ac-coupled through high voltage capacitor CF on the EHT filter board to the CRT focus electrode, G4. 5.19-9
DIAGNOSTICS SERVICE AIDS Level 0 Level 1 Linearity There are no Level 0 diagnostics for the CRT. The level 1 Graphics/Video diagnostic tests enable the monitor to be tested and calibrated. The tests offered are as follows: Linearity Colour Blocks B/W Blocks Contrast Beep With the exception of the Beep test, all the tests can be cancelled by selecting the CNCL option. Looping is only allowed on the Beep test. When the Linearity test is selected the H character is displayed in all positions on the CRT. Colour Blocks The Colour Blocks test is used to verify the overall graphic colour quality and displays colour bars on the CRT. NOTE: As the CRT is a monochrome CRT, the colour bars appear as different intensities of greyscale. B/W Blocks The B/W Blocks test displays four alternate black and white blocks on the CRT. Contrast Beep The Contrast test displays a white screen and black border, and is used to set up balance, brightness and tint. The Beep test emits a beep tone. ERROR REPORTING There is no error reporting applicable to the CRT. STRAPPING All the jumpers on the monitor are implemented with ero ohm resistors and should not be removed. FUSE There is one fuse on the monitor, F1, which is located on the scan board and is rated at 2.5 A, 250 V. 5.19-10
ASSEMBLY AND DISASSEMBLY SAFETY Read the following safety notes carefully before attempting to service the monitor. The scan board generates extremely high voltages for the CRT, in particular: 20 kv for the final anode 5 kv to 6 kv for the focus grid (G4) 700 V for the screen grid (G2). The anode and focus voltages are applied through the EHT filter board, and the screen grid voltage is applied through the video amplifier, therefore great care must be taken when handling the scan board, EHT filter and video amplifier. WARNING The CRT anode retains a potentially lethal voltage even when the monitor is turned off. The following procedure must ALWAYS be observed prior to disconnection of the EHT cap or any other task which requires the CRT to be handled: 1. Connect a clip lead or heavy gauge wire to chassis ground. 2. Connect the other end of the lead to the shaft of a flat blade screwdriver that has an insulated handle. 3. Keeping well clear of both the wire and the screwdriver shaft, insert the blade of the screwdriver under the EHT cap and make contact with the anode terminal. Depending on the amount of charge present on the anode, a distinct snap may be heard as the CRT discharges. 5.19-11
It should be noted that despite correct performance of the CRT discharge procedure, the CRT bulb capacitance can accumulate charge as the discharge stresses are relaxed. Therefore, ELECTRIC SHOCK HAZARD IS ALWAYS PRESENT WHEN HANDLING THE CRT. The following guidelines must also always be observed: Do not dispose of the CRT by breaking it, unless wearing safety glasses and protective clothing. If it becomes necessary to remove the CRT from its mountings within the monitor, under no circumstances should leverage be applied to the CRT. Never apply pressure or leverage to the tension band. If the tension band is moved it will reduce or remove the implosion protection. NOTE: Before opening any part of the monitor, remove the power cable from the connector on the top of the monitor. The monitor includes critical mechanical and electrical parts which are essential for X-radiation safety. Replace all critical components (marked with a 1 ) only with the exact replacement parts named in the Parts Identification Manual. Refer to the exploded view of the monitor assembly on fold out FO-2 at the rear of this chapter, and the interconnection assembly diagram shown below, while following the removal procedures. Numbers in brackets refer to the interconnecting wire numbers as shown in the diagram below. 5.19-12
NOTE: Assembly of the monitor is the reverse of the disassembly procedures. 5.19-13
REMOVAL OF TOP COVER Unscrew the six screws located on the top of the monitor and lift off the cover. Removal of the CRT 1. Disconnect the power to the monitor. 2. Remove the top cover. 3. Discharge the anode by following the CRT discharge procedure detailed previously. Remove the EHT cap from the anode of the CRT. 4. Unscrew the four screws which attach the left hand plate to the monitor. Slide the plate to the rear of the monitor and remove it by tilting it outwards from the front of the monitor. 5. Remove the video amplifier board from the CRT base. Remove the CRT ground wire (6), connected to the CRT braid, from the video amplifier board and the EHT filter ground wire. 6. Disconnect the deflection yoke wiring harness (1) from the connector D on the scan board. 7. Unscrew the four hex nuts, one in each corner of the CRT, and lift the CRT out of the casing. CAUTION As the CRT and the brightness sensor are a matched pair the brightness sensor must also be removed. The replacement CRT must have its matched brightness sensor installed. Removal of the Scan Board The scan board is removed as follows: 1. Disconnect the power to the monitor. 2. Remove the top cover. 3. Discharge the anode by following the CRT discharge procedure detailed previously. 4. The scan board is attached to the left hand plate. Unscrew the four screws which attach the left hand plate to the monitor. Slide the plate to the rear of the monitor and remove it by tilting it outwards from the front of the monitor. 5. Using pliers, remove the EHT lead from capacitor CE on the EHT filter board, by turning cap A counterclockwise and pulling the EHT lead out of the EHT filter board. 6. Disconnect the following wires: The focus lead (11) from capacitor CF on the EHT filter board The wiring harness (1) from the connector D on the scan board The wiring harness (5) from the connector C on the scan board The wiring harness (4) from the connector A on the scan board The wiring harness (2) from the connector B on the scan board The ground lead (3) from the GND tab on the scan board The wiring harness (8) from the connector A on the EHT filter board. 7. Remove the scan board by lifting it off the three stand-offs on the left hand plate and unscrewing the fourth stand-off which is attached to the LOPT, T2. 5.19-14
Removal of the Video Amplifier Board The video amplifier board is removed as follows: 1. Disconnect the power to the monitor. 2. Remove the top cover. 3. Discharge the anode by following the CRT discharge procedure detailed previously. 4. Unscrew the four screws which attach the left hand plate to the monitor. Slide the plate to the rear of the monitor and remove it by tilting it outwards from the front of the monitor. 5. Remove the video amplifier board from the CRT base, and disconnect the following: The wiring harness (5) from the connector C on the scan board. The ground lead (3) from the GND tab on the scan board. The ground lead (6) from the ground tab on the video amplifier board. The focus lead (12) from capacitor CF on the EHT filter board. 6. Lift the board out of the monitor. Removal of the Video Pre-amplifier Board The video pre-amplifier board is removed as follows: 1. Disconnect the power to the monitor. 2. Remove the top cover. 3. Disconnect the following: The wiring harness (4) from the connector A on the scan board. The wiring harness (7) from the connector A on the video pre-amplifier board. 4. Remove the two locking screws which hold the 15 pin D-type connector to the top of the rear plate. 5. Lift the board out of the monitor. Removal of the EHT Filter Board The EHT filter board is removed as follows: 1. Disconnect the power to the monitor. 2. Remove the top cover. 3. Discharge the anode by following the CRT discharge procedure detailed previously. Remove the EHT cap from the anode of the CRT. 4. Using pliers, remove the EHT lead from capacitor CE on the EHT filter board, by turning caps A and B counterclockwise, and pulling the EHT lead out of the EHT filter board. 5. Disconnect the following: The ground lead (9) from the CRT braid (6). The wiring harness (8) from the connector A on the EHT filter board. The dynamic focus lead (10) from the pin DF on the EHT filter board. 6. Unscrew the two screws, one holding the EHT filter board to the monitor and the other screwed to capacitor CE. Lift the board out of the monitor. 5.19-15
ADJUSTMENTS In the event of repair and/or revision to the monitor, the adjustment procedures detailed below should be followed. NOTE: The adjustable parameters are to some extent interactive and it may be necessary to repeat sections of the procedure to obtain optimum results. The interconnection assembly diagram shown previously, shows all the adjustable devices and their locations on the assembly boards. The metal plates diagram below shows the locations of the controls and the connectors. NOTE: For proper adjustment of the monitor, disconnect the photoresistor board from the PHOTORES connector on the top of the monitor and replace it with a 3K3 1/4 W 5% resistor. 5.19-16
Test Equipment To carry out the adjustments, the following equipment is required: Digital multimeter to measure up to 2000 Vdc Quantum colour character generator, model 801C Non-inductive screwdriver and insulated screwdriver for adjustments where required Stabilied power supply +24 ± 0.2 Vdc capable of providing 2.0 amps Dual trace oscilloscope with 10:1 probes Photometer with a 127 mm (5 in.) field of view. NOTE: For adjustments with the monitor installed in the host terminal, the character generator and the power supply will not be required. In this case, the three modes of operation are obtained by running the diagnostics tests for the monitor to produce the most appropriate test pattern. Set Up of the Character Generator The Quantum character generator is set up to obtain the following data: Mode 1 (640 x 400) Horiontal: Dots/char. = 8 Total chars. = 100 Displayed chars. = 80 Drive delay = 82 Drive width = 12 Vertical: Lines/char. = 12 Total lines/char. = 453 Displayed rows = 32 Drive delay = 34 Drive width = 9 H = 69.48 kh = 31.475 MH = 25.176 Horiontal sync = -ve Vertical sync = +ve. Mode 2 (640 x 350) Horiontal: Dots/char. = 8 Total chars. = 100 Displayed chars. = 80 Drive delay = 82 Drive width = 12 Vertical: Lines/char. = 12 Total lines/char. = 453 Displayed rows = 28 Drive delay = 32 Drive width = 9 5.19-17
Warm Up H = 69.47 kh = 31.475 MH = 25.176 Horiontal sync = +ve Vertical sync = -ve. Mode 3 (640 x 480) Horiontal: Dots/char. = 8 Total chars. = 100 Displayed chars. = 80 Drive delay = 82 Drive width = 12 Vertical: Lines/char. = 12 Total lines/char. = 525 Displayed rows = 39 Drive delay = 40 Drive width = 2 H = 59.95 kh = 31.475 MH = 25.176 Horiontal sync = -ve Vertical sync = -ve. Apply power to the 2 pin power input connector. Apply the cross hatch test pattern, mode 3, to the 15 pin D-connector. Allow the monitor to warm up for 5 to 10 minutes before making any adjustments. Set the CONTRAST control (VR1 on the video pre-amplifier board) to 75% of it's maximum, and the BRIGHT control (VR9 on the scan board) so that no background raster appears (it may be necessary to adjust the SUB BRIGHT control (VR10 on the scan board)). If no image is obtained, refer to the section headed TROUBLESHOOTING INFO. Horiontal Hold 1. Short together the two pins marked P1 and P2 on the scan board. 2. Adjust VR1 (H.HOLD) on the scan board, until the entire display drifts slowly across the screen. Vertical Hold Adjust VR8 (V.HOLD) on the scan board, so that the display gets locked when it is rolling from the top to the bottom of the screen. Horiontal Phase This adjustment can be used to centre the display horiontally on the screen, within a limit of ± 2 mm. If the display is off-centre, ensure that the raster is properly centred with respect to the CRT face plate. This can be adjusted using the centring magnets on the deflection yoke (refer to the deflection yoke adjustment procedure). 5.19-18
1. On the scan board, adjust VR9 (BRIGHT) so that the background raster is visible. If it can not be seen, adjust VR10 (SUB BRIGHT), to obtain the background raster. 2. Adjust VR2 (H.PHASE) so that the image is at the centre of the screen (see diagram below). Horiontal Linearity Using a non-inductive screwdriver, adjust L2 (H.LIN) on the scan board, until the corresponding vertical columns of the cross hatch pattern are of equal width, measured along the centre of the screen. NOTE: Horiontal linearity is interactive with horiontal width, therefore both H.LIN and H.WIDTH may require adjustment. Horiontal Width Adjust L1 (H.WIDTH) on the scan board, so that the horiontal sie of the display measured along the centre of the screen (assuming that the side pincushion and the geometry distortion is correctly adjusted) is 180 ± 2 mm. Vertical Linearity Adjust VR7 (V.LIN) on the scan board, so that the horiontal rows of the cross hatch pattern, on the upper and lower halves of the screen, are of equal height. NOTE: Horiontal linearity is interactive with horiontal width, therefore both H.LIN and H.WIDTH may require adjustment. 5.19-19
Vertical Height (Mode 1) 1. Apply mode 1 to the monitor. 2. Adjust VR5 (V.HEIGHT - 400 LINES) on the scan board, so that the vertical sie of the display, measured along the centre of the screen, is 130 ±2 mm. Vertical Height (Mode 2) 1. Apply mode 2 to the monitor. 2. Adjust VR4 (V.HEIGHT - 350 LINES) on the scan board, so that the vertical sie of the display, measured along the centre of the screen, is 130 ±2 mm. Vertical Height (Mode 3) 1. Apply mode 3 to the monitor. 2. Adjust VR6 (V.HEIGHT - 480 LINES) on the scan board, so that the vertical sie of the display, measured along the centre of the screen, is 130 ±2 mm. Vertical Shift/ Adjust VR3 (V.SHIFT) on the scan board, so that the display is vertically centred on the screen. Sub-brightness 1. Turn VR9 (BRIGHT) on the scan board to maximum. 2. Adjust VR10 (SUB BRIGHT) so that the background raster just appears. Focus 1. Apply the H pattern to the monitor. 2. Set VR1 (CONTRAST) on the video pre-amplifier board, to 75% of its maximum. 3. Adjust VR9 (BRIGHT) on the scan board to give a bright enough display. 4. Adjust VR11 (FOCUS) on the video amplifier board, for the best focus over the entire screen. NOTE: The BRIGHT control may have to be readjusted for better viewing. Overvoltage or X-ray Radiation Protection 1. Connect the voltmeter to the test pin marked ADJUST 7V on the EHT filter board. 2. Turn VR1 on the EHT filter board fully counterclockwise so that the voltmeter reads approximately 5.7 V. 3. Turn VR1 clockwise until the voltmeter reads 8.0 V. The monitor should switch off. 4. Disconnect the +24 Vdc supply to the monitor, turn VR1 fully counterclockwise, and re-apply the power. 5. Set VR1 (CONTRAST) on the video pre-amplifier to minimum so that there is no display on the screen. 6. Adjust VR1 on the EHT filter so that the voltmeter reads 6.8 V +0 V/-0.1 V. 5.19-20
Brightness Sensor 1. Apply a non-intensified (0.45 Vp-p) video input signal to the monitor. 2. Connect a 10:1 oscilloscope probe to the collector of TR2 on the video amplifier board. 3. Disconnect the brightness sensor from the connector on the top of the monitor, and connect a 3k3 resistor in its place. 4. Set VR1 (CONTRAST) on the video pre-amplifier so that the oscilloscope reads 40 Vp-p (black-white). 5. Remove the resistor and reconnect the brightness sensor. 6. Cover the brightness sensor with black tape. 7. Adjust VR1 on the brightness sensor so that the oscilloscope reads 15 Vp-p (black-white). 8. Remove the tape from the brightness sensor. CAUTION If the brightness sensor fails the CRT must also be removed and a matched CRT and brightness sensor installed. Specific Luminance Value of Peak White The CONTRAST and BRIGHT controls can be adjusted to obtain a specific value of peak white as follows: 1. Using the character generator in mode 3, apply either a 0.45 Vp-p (nonintensified) or 0.7 Vp-p (intensified) video signal to produce four white rectangular blocks as shown below: 2. Connect a 10:1 oscilloscope probe to the collector of TR2 on the video amplifier board. 3. Disconnect the brightness sensor from the connector on the top of the monitor, and replace with a 3k3 resistor. 4. Set VR1 (CONTRAST) on the video pre-amplifier so that the oscilloscope reads 40 Vp-p (black-white). 5. Set VR9 (BRIGHT) on the scan board, to maximum. 6. Adjust VR10 (SUB BRIGHT) on the scan board, so that the background raster is just visible. 7. Place the photometer so that its sensor is located at the centre of one of the white squares. Adjust the BRIGHT control until the photometer reads 50 fl ± 10% (172 cd.m -2 ) with a non-intensified input signal and 80 fl ± 10% (275 cd.m -2 ) with an intensified input signal. 5.19-21
Deflection Yoke If the deflection yoke is replaced, the following adjustments will be necessary: Image orientation Picture centring Pincushion distortion correction. The deflection yoke has a strong inherent pin-cushion which is corrected by four bar magnets as shown below: The four magnets are pre-aligned to obtain the maximum pincushion. 1. Remove the power from the monitor. 2. Remove the top cover. 3. Discharge the anode by following the CRT discharge procedure detailed in the safety section under the heading ASSEMBLY AND DISASSEMBLY. 4. Remove any circular magnets mounted on the stalks of the deflection yoke. 5. Carefully push the deflection yoke so that it touches the rear of the CRT. Tighten the clamp screw so that the deflection yoke can not turn or slip out by itself. 5.19-22
6. Adjust the centring magnets, one opposite to the other, to obtain the minimum magnetic field strength. 7. Reapply power to the monitor and apply a cross hatch pattern. 8. Rotate the deflection yoke until the central horiontal and vertical crossing lines are horiontal and vertical, or, the top and bottom edges of the video image field are parallel with the horiontal edges of the CRT faceplate. 9. Carefully tighten the clamp screw to fix the deflection yoke to the CRT neck, ensuring that it remains tight up to the CRT. 10. Adjust the centring magnets to align the video image with the centre of the CRT faceplate. NOTE: To minimie the curvature of the horiontal and vertical lines, the video image must be centred with respect to the raster by adjusting both the V.SHIFT and H.PHASE controls. 5.19-23
11. To correct the north-south trapeium distortions caused by the deflection yoke and the CRT, the north-south bar magnets should be adjusted as shown in the diagram below: 5.19-24
12. To correct the east-west trapeium distortions caused by the deflection yoke and the CRT, the east-west bar magnets should be adjusted as shown in the diagram below: 13. If the required tolerances can not be met using only the four bar magnets, up to 12 additional stalk magnets can be employed which affect the areas shown in the diagram below. Each stalk is identified by a capital letter. The stalk magnets are either 4.2 mm (14 ± 0.5 Gauss) or 6 mm (18 ± 0.5 Gauss). 5.19-25
14. Magnets A, D, G and L correct both horiontal and vertical seagull and pin-cushion distortions as shown below: 15. Magnets B, F, H and N correct the edges of the north and south lines as shown below: 5.19-26
16. Magnets C, E, I and M correct the edges of the east and west lines as shown below: 17. Switch off the monitor and make sure that the deflection yoke clamp screw is well tightened. Fix the four bar magnets, the centring magnets and the additional stalk magnets using a blob of enamel paint. TROUBLESHOOTING INFO TOOLS AND EQUIPMENT To troubleshoot the monitor, the following tools and equipment are required: Digital multimeter to measure up to 2000 Vdc. Quantum colour character generator. Non-inductive screwdriver and insulated screwdriver for adjustments where required. Dual trace oscilloscope with 10:1 probes. Stabilied power supply, +24 ± 0.2 Vdc capable of providing 2.0 amps. NOTE: For adjustments with the monitor installed in the host terminal, the character generator and the power supply are not required. WARNING The CRT anode retains a potentially lethal voltage even when the monitor is turned off. The EHT discharge procedure detailed in the safety section under the heading ASSEMBLY AND DISASSEMBLY must ALWAYS be observed prior to disconnection of the EHT cap or any other task which requires the CRT to be handled. Take care also when servicing or handling the scan board, video amplifier board and EHT filter. 5.19-27
DIAGNOSTIC PROCEDURES Overvoltage If an overvoltage occurs and the EHT exceeds 21.5 kv, the X-Ray protection circuit will switch off the EHT. The monitor can then only be reset by switching off and on again. NOTE: This condition will re-occur unless the cause of the over-voltage condition has been removed. 5.19-28
No Raster 5.19-29
No Picture - Raster OK 5.19-30
Abnormal Video on CRT - Too Bright or Too Dark 5.19-31
No Blanking - Visible Retrace Line on the Back Raster Bad Horiontal and Vertical Synchroniation Horiontal 5.19-32
Vertical Abnormal Vertical Height in 480 Line Mode 5.19-33
Vertical Mode Poor Focus - Static Poor Focus - Dynamic 5.19-34
CONNECTOR ASSIGNMENT EXTERNAL CONNECTORS The 10 inch sunlight viewable monochrome monitor has three external connectors as follows: Video and Sync Connector Video and sync data is input to the monitor through a 15 pin D-type connector with the following pinout: Power Input Connector Power is input to the monitor via a twisted pair connected to a two pin Molex connector. 1 +24 V RTN 2 +24 V Brightness Sensor Connector The brightness sensor connects to a two pin connector with the following pinout: 1 BRIGHTNESS 2 GND SCHEMATIC DIAGRAMS Fold-out sheet FO-1 details the schematic diagram for the monitor. Fold-out sheet FO-2 details the exploded view of the monitor assembly. 5.19-35
5.19-36