Medion S790V-1, MD1798 Schematic
SERVICE MANUAL
COLOR MONITOR
Medion S790V MD1798 OA
F/N : S790V-01-A
Date : Sep-05-01
Version : A01
TABLE OF CONTENTS
PAGE
1. SPECIFICATIONS ..................................................................................................... 3-4
2. PRECAUTION AND NOTICES ................................................................................ 5
2-1 SAFETY PRECAUTIONS .............................................................................. 5
2-2 PRODUCT SAFETY NOTICE ....................................................................... 5
2-3 SERVICE NOTES ........................................................................................... 5
2-4 HIGH VOLTAGE WARNING ....................................................................... 6
3. OPERATING INSTRUCTIONS ................................................................................ 7
4. ADJUSTMENT .......................................................................................................... 8
4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS ............................... 8
4-2 MAIN ADJUSTMENTS ................................................................................. 8
4-3 ADJUSTMENT METHOD ............................................................................. 8-11
5. CIRCUIT DESCRIPTION .......................................................................................... 11-14
6. TROUBLE SHOOTING CHART .............................................................................. 15
6-1 NO RASTER, CRT RELATIVE CIRCUIT PROBLEMS .............................. 15
6-2 ABNORMAL DISPLAY ................................................................................. 17
6-3 NO BLANKING ........................................................................................... 18
6-4 HOR. /OSC /DEF /HV CIRCUIT FAULT ...................................................... 18
6-5 ABNORMAL HORIZONTAL DEFLECTION .............................................. 19
6-6 ABNORMAL VERTICAL SCANNING ........................................................ 20
6-7 SIDE-PIN CUSHION DISTORTION ............................................................. 20
6-8 POOR FOCUS ................................................................................................. 21
6-9 POWER SUPPLY TROUBLE SHOOTING CHART .................................... 21
7. MECHANICAL OF CABINET FRONT DIS-ASSEMBLY...................................... 22
8. PARTS LISTING ....................................................................................................... 23-38
9. IC BLOCK DIAGRAMS............................................................................................ 39
11. PCB LAYOUT ............................................................................................................ 44
12. SCHEMATIC DIAGRAM ......................................................................................... 46
1. SPECIFICATIONS FOR MD1798 OA SERIES COLOR MONITOR
1. CRT : 43.2CM(17") 90 Deflection, 29mm Neck, Pure flat 0.25mm Dot Pitch, Non-Glare Screen
2. Viewable image Size: 40.6CM (16") diagonal
3. Display Color: Unlimited Colors
4. External Controls:
Power On/Off, OSD key, Function knob: Contrast, Brightness, H-Size, H-Center, V-Size, V-Center, ZOOM,
Pincushion, Trapezoid, Pin-Balance, Parallelogram, Rotation, Moire Reduce, Recall, Degaussing, Color
Temperature, use color, exit , language .
5. Input Video Signal
Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 Mode 6
RGB Analog RGB Analog RGB Analog RGB Analog RGB Analog RGB Analog
Horiz. Sync: TTL Level TTL Level TTL Level TTL Level TTL Level TTL Level
Negative Negative Negative Positive Positive Positive
Vert. Sync: TTL Level TTL Level TTL Level TTL Level TTL Level TTL Level
Positive Negative Negative Positive Positive Positive
Horizontal: 720 (H) 640 (H) 640 (H) 800 (H) 800 (H) 800 (H)
Vertical : 400 (V) 480 (V) 480(V) 600(V) 600(V) 600(V)
Fh (kHz): 31.32 31.46 43.269 46.875 53.674 62.966
Fv (Hz) : 70 59.5 85.008 75 85.061 99.472
Mode 7 Mode 8 Mode 9 Mode 10 Mode 11 Mode 12 Mode 13
RGB Analog RGB Analog RGB Analog RGB Analog RGB Analog RGB Analog RGB Analog
Horiz. Sync: TTL Level TTL Level TTL Level TTL Level TTL Level TTL Level TTL Level
Positive Positive Negative Positive Positive Positive Positive
Vert. Sync: TTL Level TTL Level TTL Level TTL Level TTL Level TTL Level TTL Level
Positive Positive Negative Positive Positive Positive Positive
Horizontal: 1024 (H) 1024 (H) 1024 (H) 1280 (H) 1280 (H) 1280 (H) 1600 (H)
Vertical : 768 (V) 768 (V) 768 (V) 960 (V) 1024 (V) 1024 (V) 1200 (V)
Fh (kHz): 60.023 68.677 80.468 85.935 79.976 91.148 93.750
Fv (Hz) : 75.029 84.997 99.836 85 75.025 85.000 75
6. Display Size
Horizontal: 310 mm for other Preset Modes
Vertical: 230 mm for other Modes
Horizontal: 300 mm for 1280x1024 Preset Modes
Vertical: 240 mm for 1280x1024 Modes
6. Scanning Frequencies
Horizontal:
Vertical:
8. Factory Preset Timings: 13
User Timings: 20
9. Misconvergence
Center: 0.25 mm Max.
30KHz ~ 98KHz
50 Hz ~ 160 Hz
Corner: 0.35 mm Max.
10. Dot Rate : 203 MHz
11. Power Source:
Switching Mode Power Supply
AC 100 ~240V, 50/60Hz Universal Type
12. Operating Temperature: 0oC to 40 oC Ambient
13. Humidity : 10% to 85% Relative, Non-Condensing
14? Weight: 16.0 Kgs(Net), Kgs(Gross)
15. Dimensions Monitor:
Carton: 570mm(W) × 450mm(H) × 515 mm (D)
Monitor: 410mm(W) × 411mm(H) × 430mm(D)
16. External Connection :
15 Pin D-type Connector AC Power Cord
17. Regulations: -EN60950+ZH 1/618(VBG104) :GS-MARK
-UL1950
-CSA22.2 NO.950
-VDE 0860 (implosion pritection)
-CE
-TCO99
-CB-Certificate and test report according to IEC950
2. PRECAUTIONS AND NOTICES
2-1 SAFETY PRECAUTIONS
1. Observe all caution and safety related notes located inside the display cabinet.
2. Operation of the display with the cover removed, may cause a serious shock hazard from the display power
supply. Work on the display should not be attempted by anyone who is not thoroughly familiar with precautions
necessary when working on high voltage equipment.
3. Do not install, remove or handle the picture tube in any manner unless shatter-proof goggles are worn. People
who are not so equipped should be kept away while handling picture tube. Keep picture tube away from the
body while handling.
4. The picture tube is constructed to limit X-RAY radiation to 0.5 mR/HR. For continued protection, use the
designated replacement tube only, and adjust the voltages so that the designated maximum rating at the anode
will not be exceeded.
5. Symbol “ “ means safety relative parts. The use of substitute replacement parts which do not have the same
characteristics as specified in the parts list may create shock, fire or explode etc.
6. Symbol “ ” means X-ray relative parts. Before replacing any of these components please read the parts
list
in this manual carefully to avoid creating higher anode voltage or x-ray. Especially for sealed controls,
such as VR901, VR902, VR401 and FBT screen VR etc, which were sealed by the manufacturer once their
optimum position has been set, please don’t dismantle them as your likes, otherwise you will break or
damage the component. If you need replace the parts with sealed control, please adjust the relative VR to
make sure the B+ voltage under 61.0VDC and well seal it with A+B glue or equivalent, which you can not
move away with one screw driver.
7. Before returning a serviced display to the customer, a thorough safety test must be performed to verify that the
display is safe to operate without danger or shock. Always perform an AC leakage current check on the exposed
metallic parts of the cabinet, such as screw heads.
Test method for current leakage is described as follow.
(a) Plug the AC line cord directly into rated AC outlet (do not use a line isolation transformer during this
check).
(b) Use an AC voltmeter having 5000 ohms per volt or with more sensitivity in the following manner:
Connect a 1500 ohms 10 Watt resistor, paralleled by a 0.15UF, AC type capacitor between a known good
earth ground (water pipe, conduit, etc.) and the exposed metallic parts simultaneously. Measure the AC
voltage across the combination of 1500 ohms resistor and 0.15UF capacitor.
(c) Reverse the AC plug at the AC outlet and repeat AC voltage measurements for each exposed metallic part.
(d) Voltage measured must not exceed 0.5 volts RMS. This corresponds to 0.35 milliamp AC. Any value
exceeding this limit constitutes a potential shock hazard and must be corrected immediately.
2-2 PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in this chassis have special safety visual inspections and the protection afforded
by them cannot necessarily be obtained by using replacement components rated for higher voltage, wattage, etc.
Before replacing any of these components read the parts list in this manual carefully. The use of substitute
replacement parts which do not have the same safety characteristics as specified in the parts list may create shock,
fire, X-RAY radiation or other hazards.
2-3 SERVICE NOTES
1. When replacing parts or circuit boards, clamp the lead wires around terminals before soldering.
2. When replacing a high wattage resistor (more than 1/2W of metal oxide film resistor) in circuit board, keep the
resistor about 10mm (1/2 in) away from circuit board.
3. Keep wires away from high voltage or high temperature components.
4. Keep wires in their original position so as to reduce interference.
Operation of monitor outside of cabinet or with back removed may cause a serious shock hazard. Work on this model
should only be performed by those who are thoroughly familiar with precautions necessary when working on high
voltage equipment.
Exercise care when servicing this chassis with power applied. Many B plus and high voltage terminals are exposed
which, if carelessly contacted, can cause serious shock or result in damage to the chassis. Maintain interconnecting
ground lead connections between chassis and picture tube dag when operating chassis.
Certain HV failures can increase X-ray radiation. Monitor should not be operated with HV levels exceeding the
specified rating for the chassis type. The maximum operating HV specified for the chassis used in this monitor is
25.5KV ± 0.8KV
with a line voltage of 120/240 VAC. Higher voltage may also increase possibility of failure in HV supply.
It is important to maintain specified values of all components in the horizontal and high voltage circuits and
anywhere else in the monitor that could cause a rise in high voltage or operating supply voltages. No changes should
be made to the original design of the monitor. Components shown in the shaded areas on the schematic should be
replaced with exact factory replacement parts. The use of unauthorized substitute parts may create a shock, fire or
other hazard.
To determine the presence of high voltage, use an accurate, high impedance, HV meter connected between second
anode lead and CRT dag grounding device. When servicing the High Voltage System, remove static charge from it
by connecting a 20K ohm resistor in series with an insulated wire (such as a test probe) between picture tube dag and
2nd anode lead.(AC line cord disconnected from AC power outlet.)
The picture tube used in this monitor employs integral implosion protection. Replace with tube of the same type
number for continue safety. Do not lift picture tube by the neck. Handle the picture tube only after discharging the
high voltage completely.
5
3. OPERATING INSTRUCTIONS
This procedure gives you instructions for installing and using the 7K color display.
1. Position the display on the desired operation and plug the power cord into a convenient AC outlet. Three-wire
power cord must be shielded and is provided as a safety precaution as it connects the chassis and cabinet to the
electrical conduit ground. If the AC outlet in your location does not have provisions for the grounded type plug,
the installer should attach the proper adapter to ensure a safe ground potential.
2. Connect the 15-pin color display shielded signal cable to your signal system device and lock both screws on the
connector to ensure firm grounding. The connector information is as follow:
PIN NO.
DESCRIPTION
1. RED 9. NC
2. GREEN 10. GND
3. BLUE 11. SYNC. GND
4. GND 12. SDA
5. GND 13. HORIZ. SYNC
6. GND-R 14. VERT. SYNC (*VCLK)
7. GND-G 15. SCL
8. GND-B
3. Apply power to the display by turning the power switch to the "ON" position and allow about thirty seconds for
display tube warm-up. The Power-On indicator lights when the display is on.
4. With proper signals feed to the display, a pattern or data should appear on the screen, adjust the brightness and
contrast to the most pleasing display.
5. This monitor has power saving function following the VESA DPMS. Be sure to connect the signal cable to the
PC.
1
6
11 15
10
15 - Pin Color Display Signal Cable
PIN NO.
DESCRIPTION
4. ADJUSTMENT
4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS
1. Approximately 30 minutes should be allowed for warm up before proceeding.
2. Adjustments should be undertaken only on those necessary elements since most of them have been carefully
preset at the factory.
4-2 MAIN ADJUSTMENTS
NO. FUNCTION LOCATION DESIGNATION
1. 14.5V ADJ PCB - MAIN VR901
2. B + ADJ PCB - MAIN VR902
3. SCREEN ADJ FLY BACK TRANS T402
4. FOCUS ADJ FLY BACK TRANS T402
5. ABL ADJ PCB - MAIN VR701
6. SUB-BRIGHTNESS ADJ PCB - MAIN VR702
-MENU PCB - MAIN (SW103)
-UP PCB - MAIN (SW105)
7. FUNCTION ADJ -DOWN PCB - MAIN (SW104)
-EXIT PCB - MAIN (SW102)
4-3 ADJUSTMENT METHOD
1. 14.7V, B + & HV voltage adjustment:
A. Chrome-2000 Signal generator or PC equivalent set mode 1, VGA 640X480 cross hatch pattern .
B. Connect a DC Volt meter between TP901 or D922 cathode and ground, then adjust VR901 to be 14.7VDC.
C. Connect a DC Volt meter between TP902 or D925 cathode and ground, then adjust VR902 to be 59.5VDC.
D. Connect a DC Volt meter between TP701(G1) and ground, Brightness set to max. Then adjust VR702 to be -
40 VDC.
2. Factory preset Timings Adjustment:
A. Press MENU Key to show OSD window press Up or Down Key to switch the functional controls.
B. Press the Up Key to select the "ZOOM" function, then press the MENU Key. While do not release the MENU
Key until the OSD window changed to the Factory preset window.
C. The Factory preset window contains the following functional controls. Select one of the control. Then press the
Up/Down Key to adjust it's value for the optimum picture.
MENU Key to Quit the OSD window. Mean while the new setting data will be saved in the memory.
D. To switches the input signal to the other Timing Mode. Please follow step C to get the optimum picture.
E. Select the " " RETURN function and press the MENU Key, then the Factor Preset window will be
returned to the original OSD window.(user's operating condition)
F. The setting data of the CONTRAST, BRIGHTNESS, PIN-BALANCE, PARALLELOGRAM, ROTATION,
COLOR TEMPERATURE are common mode saved in the memory. Don't needed adjust it individual at every
timing Mode and save in the memory.
G. BI, HS, HP: Model select: for factory only, service engineer can't change.
BI
HS
HP
FACTORY PRESET
H: 36.51kHz
V: 51.34Hz
VcVs
9300
6500
Tm
080
CONTRAST
BRIGHTNESS
H-CENTER
H-SIZE
V-CENTER
V-SIZE
ZOOM
Top corner
Bottom corner
9300
H-MOIRE REDUCE
V-MOIRE REDUCE
R-GAIN
G-GAIN
B-GAIN
R-BIAS
G-BIAS
R-BIAS
COLOR TEMPERATURE
Vs
Vc
BI
PINCUSHION
TRAPEZOID
PIN-BALANCE
PARALLELOGRAM
ROTATION
Sub V-size
Sub V-center
Burning picture on/off switch
6500
HP
HS
COLOR TEMPERATURE
DEGAUSS
OSD EXIT
RETURN
Vs Linear
Vc Linear
H-size limitation
H-size compensation
3. White Balance, Luminance adjustment:
A. Bias (Low Luminance) adjustment:
(a) Set mode 8 1024×768 Fh: 68.7KHz full white pattern.
(b) To make the adjustment condition is under the Factory preset window.
Same as step 2-C.
(c) Warm up more than 20 minutes.
(d) Brightness set to maximum. Contrast set to min. full white pattern, then adjust FBT screen VR
to make Y= 1.5~8.5 cd/m
(e) Brightness set to raster just cutoff, adjust contrast to be 12 cd/m
2
.
2
, then adjust G-Bias , B-Bias
.
, R-Bias , to make the setting value is(20), then adjust the R.G.B Bias individual to the
color temperature x= 275 ± 10, y= 295 ± 10.
B. Gain (High light) adjustment:
(a) Set mode 2 640×480 Fh: 31.5KHz full white pattern.
(b) Brightness set to raster just cutoff and set the contrast to max.
(c) Adjust G-Gain , B-Gain , R-Gain , to make color temperature x=283 ± 10,
y=297 ± 10.
C. Recheck item A&B to make sure both of them in spec. Finally select OSD function to the 9300°K function,
then press the MENU Key. To make the setting data saved in the memory.
D. The adjustment of 6500°K white Balance, May follow step A ~ C , with the x=313 ± 10, y=329 ± 10.
E. Full white luminance:
(a) Set mode 8 1024×768 Fh: 68.67KHz full white pattern.
(b) Image Size : H:310±4mm V:230±4mm.
(c) Brightness set to raster just cut off and set the contrast to max.
(d) Adjust VR701 to the luminance at 30 FL ± 2FL.
4. Focus Adjustment:
A. Set mode 8 1024×768 Fh: 68.67 KHz with character full page.
B. Adjust brightness to center and contrast to max.
C. Then adjust focus VR1 to a fine vertical line.
D. Adjust focus VR2 to a fine horizontal line.
E. Repeat step C & D..
5. Purity Adjustment
A. Be sure that the display is not being exposed to any external magnetic fields.
B. Ensure that the spacing between the Purity, Convergence, Magnet, (PCM), assembly and the CRT stem is
29mm .(See below diagram)
C. Produce a complete, red pattern on the display. Adjust the purity magnet rings on the PCM assembly to obtain a
complete field of the color red. This is done by moving the two tabs in such a manner that they advance in an
opposite direction but at the same time to obtain the same angle between the two tabs, which should be
approximately 180'.
D. Check the complete blue and complete green patterns to observe their respective color purity. Make minor
adjustments if needed.
RELATIVE PLACEMENT OF TYPICAL COMPONENTS
Purity Magnets
6-pole Convergence Magnets
4-pole Convergence Magnets
Deflection Yoke
6. Convergence adjustment
A. Produce a magenta crosshatch on the display.
B. Adjust the focus for the best overall focus on the display.
Also adjust the brightness to the desired condition.
C. Vertical red and blue lines are converged by varying the angle between the two tabs of the 4 pole magnets on
the PCM assembly. (See above diagrams)
D. Horizontal red and blue lines are converged by varying the two tabs together, keeping the angle between them
constant.
E. Produce a white crosshatch pattern on the display.
F. Vertical green and magenta lines are converged by varying the angle between the two tabs of the 6-pole
magnets.
G. Horizontal green and magenta lines are converged by varying the two tabs together, keeping the angle between
them constant.
5. CIRCUIT DESCRIPTION
5-1 MICRO CONTROLLER CIRCUIT
MICRO Controller
The IC101 contains a 6502 8-bit CPU core, 256 bytes of RAM, 16K bytes of ROM, 2 channel A/D converters for key
detection, one 8 bit pre-loadable base timer, internal H-sync and V-sync signals processor providing mode detection,
watch- dog timer preventing system from abnormal operation, and an I2C bus interface.
H/V sync signals processor
The functions of the sync processor include polarity detection, H-SYNC & V-SYNC signals counting, Programmable
SYNC signals output, free running signal generator. Pin39/Pin40 are for the H-SYNC and V-SYNC input, Pin32/Pin33
will output the same signal as input sync signal without delay, and the polarity are setting in the positive. When no
signal input, the Pin32 will output a 60HZ V-SYNC free run signal. The Pin33 will output a 62.5KHz H-SYNC free
run signal. for the monitor testing use.
On Screen Display Controller
The IC802 is designed for display the built-in characters or fonts onto monitor screen. The display operation is by
transforming data and control information from micro controller to RAM through a serial data interface.
Pin5 is input the horizontal fly back pulse, for PLL generator tracking.
Pin7 the external data transfer through this pin to internal display registers and control registers
Pin8 the clock-input pin is used to synchronize the data transfer.
Pin10 is input the vertical flyback pulse for synchronizing the vertical position.
Pin15 is output a blanking signal to cut off external R.G.B signals of VGA while this chip is displaying characters or
windows.
Pin12 Pin13, Pin14 is used to output the OSD (B.G.R) video signal.
5-2 DEFLECTION CIRCUIT
The deflection circuit is achieved by a high performance and efficient solution IC 401 (TDA4841) for this monitor.
The concept is fully DC controllable and can be used in applications with a micro-controller solutions.
The TDA 4841 provides sync. Processing with full auto sync. capability, a flexible SMPS block and an extensive set
of geometry control facilities. Further the IC generates the drive waveforms for DC coupled vertical boosters to TDA
9302[ref Page-28].
Horizontal Oscillator
The oscillator is of the relaxation type and requires a capacitor of 10nF C403 at pin 29. The maximum oscillator
frequency is determined by a resistor R403 from pin 28 to ground. A resistor R402 from pin27 to pin28 defines the
frequency range.
PLL 1 Phase Detector
The phase detector is a standard one using switched current sources. It compares the middle of H-sync. with a fixed
point on the oscillator saw-tooth voltage. The PLL loop filter c401, R401, C402 is connected to Pin26.
PLL2 Phase Detector
This phase detector is similar to the PLL1 detector and compares the line flyback pulse at pin 1 with the oscillator sawtooth voltage. The PLL2 detector thus compensates for the delay in the external H-deflection circuit by adjusting the
phase of the HDRV output pulses. The phase between H-flyback and H-sync can be controlled at pin30.
X-ray Protection
The X-ray protection input pin2 provides a voltage detector with a precise threshold. If the voltage exceeds this
threshold for a certain time, an internal latch switches the whole IC into protection mode. In this mode several pins are
forced into defined states:
Pin6 (BDRV) is floating
Pin8 (HDRV) is floating
Pin12, 13 ( VOUT 1, 2) are floating
Pin16 (CLBL) provides a continuous blanking signal.
Vertical Oscillator
The vertical free –running frequency is determined by the resistor R608 at pin23 and capacitor C604 at pin24. Usually
the free-running frequency should be lower than the minimum trigger frequency.
5-3 TRANSISTOR & DIODE CIRCUIT
LOCATION FUNCTION AL DESCRIPTION
Q101 For LED Indicator Control
D431 Protection Diode for B+ Control
D405 Speed up for Q403
D406, D407 Supply a bias for D408
D408 Damping Diode and Modulation Diode
Q401 B+ Mute Control
Q402 Horizontal Driver
Q403 Horizontal Out Put
Q404, Q406 A differential Amp for Drive Q405
Q405 DarlingtonTransistor for H-Size Control
Q407 Horizontal Linearity Correction Control
Q412, 417,Q418,Q420
Horizontal S-Correction Control
D704 Rectifier for 250V Supply
D709 Protection Diode for Q708
D706,D708 Rectifier for -200V Supply
Q707 Picture Mute Control AMP
Q703, Q706 Brightness Control CKT
Q708 Vertical Dynamic Focus Control AMP
D901 ~ D904 Bridge Rectifier for AC Source
D909 Rectifier for Start Power Supply
D910 Clip Diode for Snubber CKT
D911 IC901 VCC Supply
LOCATION
D913 Speed UP for Q901
D914 Synchronous Trigger for Power Supply
D918 ~ D919 Rectifier for Output Voltage Supply
D921 ~ D923 Rectifier for Output Voltage Supply
D924 Clip Diode for Trigger CKT
D925 Rectifier for B+ Supply
D926, D927 Raster Position Control
ZD901 Protection Diode
ZD902 Protection Diode
ZD903 Protection Diode
Q901 MOS FET for Switching Power Control
Q904 MOS FET for PFC
Q906, Q907 Start up CKT for IC901
Q908, Q916 To Turn 6.3V Supply Off when the Off Mode is Required
FUNCTION AL DESCRIPTION
Q909, Q910 To Turn 14.5V Supply Off when the Off or Suspend Mode is Required
Q911 MOS FET for B+ Control
Q912, Q915 Push Pull Driver for Q911
Q914 Pre-Amplifier for Q912, Q915
Q853 ~ Q855 DC Restoration for CRT Bias Adjustment
6.TROUBLE SHOOTING CHART
6-1 NO RASTER, CRT RELATIVE CIRCUIT PROBLEMS
CHECK MAIN PCB POWER SUPPLY
60.5V, 14.5V, 80V
59.5V,14.7V,80V
NG
OK
CHECK THE HIGE VOLTAGE
OF CRT ABOUT 25.5 ~ 26.5KV
NG
OK
CHECK THE VOLTAGE OF CRT
HEATER ABOUT 6.3V
NG
OK
CHECK SCREEN VOLTAGE ABOUT
400V TO 700V
LESS THAN 300V
OK
CHECK POWER SAVING CIRCUIT,
H-SYNC, V-SYNC SIGNAL
OK
REFER ITEM S.M.P.S.
CHECK FAILSAFE CKT IC401
PIN 2 RELATIVE CKT.
CHECK CRT'S HEATER RELATIVE
CIRCUIT
CHECK FBT
BRIGHTNESS SET TO MAX.
THEN CHECK CRT G1 VOLTAGE
NG
OK
CHECK VOLTAGE OF THE CRT
CATHODE ABOUT 60V TO 70V
NG
CHECK BRIGHTNESS CIRCUIT
Q703, Q706, Q707 RELATIVE CKT.
REFER ITEM 8-2
"ABNORMAL DISPLAY"
Loading...