ViewSonic P774B-2NT Series Service Manual

SERVICE MANUAL

COLOR MONITOR

P774B-2NT Series

THESE DOCUMENTS ARE FOR REPAIR SERVICE INFORMATION ONLY. EVERY REASONABLE
EFFORT HAS BEEN MADE TO ENSURE THE ACCURACY OF THIS MANUAL; WE CANNOT
GUARANTEE THE ACCURACY OF THIS INFORMATION AFTER THE DATE OF PUBLICATION AND
DISCLAIMS LIABILITY FOR CHANGES, ERRORS OR OMISSIONS.

MANUFACTURE DATE: MAR.2005

1

TABLE OF CONTENTS

PAGE

1. SPECIFICATIONS .....................................................................................… 2

2. PRECAUTION AND NOTICES ...................................................................... 4

2-1 SAFETY PRECAUTIONS .................................................................... 4

2-2 PRODUCT SAFETY NOTICE ............................................................. 4

2-3 SERVICE NOTES ............................................................................... 4

2-4 HIGH VOLTAGE WARNING ............................................................... 5

3. OPERATING INSTRUCTIONS ...................................................................... 6

4. ADJUSTMENT ...........................................................................................… 7

4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS ......................... 7

4-2 MAIN ADJUSTMENTS ........................................................................ 7

4-3 ADJUSTMENT METHOD .................................................................... 7

4-4 EDID CONTENTS................................................................................ 10

5. CIRCUIT DESCRIPTION ............................................................................... 11

5-1 MICRO CONTROLLER CIRCUIT .............................…………………. 11

5-2 DEFLECTION CIRCUIT .............................……………………………. 11

5-3 TRANSISTOR & DIODE CIRCUIT .............................………………… 12

6. TROUBLE SHOOTING CHART ..................................................................... 13

6-1 NO RASTER, CRT RELATIVE CIRCUIT PROBLEMS ....................... 13

6-2 ABNORMAL DISPLAY ........................................................................ 15

6-3 NO BLANKING .................................................................................... 16

6-4 HOR. /OSC /DEF /HV CIRCUIT FAULT .............................................. 16

6-5 ABNORMAL HORIZONTAL DEFLECTION ........................................ 17

6-6 ABNORMAL VERTICAL SCANNING .................................................. 18

6-7 SIDE-PIN CUSHION DISTORTION .................................................... 18

6-8 POOR FOCUS .................................................................................... 18

6-9 POWER SUPPLY TROUBLE SHOOTING CHART ............................ 19

7. MECHANICAL OF CABINET FRONT DIS-ASSEMBLY................................. 20

8. BOM LIST..........................................................................................……… 21

9. BLOCK DIAGRAM .....................................................................…………….. 36

10. IC BLOCK DIAGRAMS................................................................................... 38

11. PCB LAYOUT ................................................................................................ 42

12. SCHEMATIC DIAGRAM ................................................................................ 44

2

1. SPECIFICATIONS FOR E70f SERIES COLOR MONITOR

1. CRT : 43.2 cm (17”) F&S high contrast CRT, 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, Degauss, H-Size, H-Center, V­Center, V-Size, ZOOM, Pincushion, Trapezoid, Pin-Balance, Parallelogram, Rotation, Color
Temperature, Moire Reduce, Recall, Language select, OSD EXIT,User

,

s Color,pincushion.

5. Input Video Signal

Factory Preset #1 #2 #3 #4

Resolution 720*400 640*480 640*480 800*600

H (KHz) 31.327 31.469 43.3 53.674

V (Hz) 69.616 59.943 85.00 85.061

Factory Preset #5

#6

#7

Resolution 1024*768

1152*864

1280*1024

H (KHz) 68.677

67.500

63.981

V (Hz) 84.997

7500

60.020

6. Display Size

Horizontal: 316 mm +/-4mm
Vertical: 236 mm +/-4mm

7. Scanning Frequencies

Horizontal: 30KHz ~ 72KHz
Vertical: 50 Hz ~ 160 Hz

8. Factory Preset Timings: 7
User Timings: 20

9. Misconvergence

A Zone: 0.30mm Max.
B Zone: 0.40 mm Max.

10. Video Bandwidth: 120 MHz

11. Power Source:
Switching Mode Power Supply
AC 100 ~240V, 50/60Hz Universal Type

12. Operating Temperature: 0°C to 40°C Ambient

13. Humidity: 5% to 85% Relative, Non-Condensing

3

14. Weight: 17. Kgs(Net), 20.5Kgs(Gross)

15. Package Specifications
Width: 540 mm
Height: 537 mm
Depth: 570mm

16. External Connection:
15 Pin D-sub Connector
AC Power Cord

17. Regulatiory/Safety

- EN 60950 + EKI-ITB 2000: GS-mark

- UL60950

- CSA 22.2 No.60950

- VDE 0860 (implosion protection)

- CE-mark

- CB-certificate and test report according to IEC60950

The model is designed to reach following approvals:

- EN 55022 class B and EN 50024 → CE-mark

- FCC class B part 15
Test procedures Standards Requirements frequency

range

Remarks

Conducted power-line
emission

EN 55022 Class B
FCC Part 15, Subq.B

150 kHz ~ 30 MHz
450 kHz ~ 30 MHz

Radiation emission EN55022 Class B

FCC Part 15,Subq.B

30 MHz ~ 1 GHz
30 MHz ~ 1 GHz

30 MHz ~ 2 GHz
if clock > 108 MHz

Electrostatic (ESD)

EN 55024

- no functional

- disturbance:

- 8 kV air discharge

Immunity to RF field
strength

EN55024

80 MHz ~ 1 GHz 3V/m Modulation

Electrical fast transient EN 55024

- no functional
disturbance:

1 kV power cord

0.5kV signal cable

Disturbance
measurement

EN 55024

Electrostatic field
magnetic field electric
field

MPR II
TCO(option)

4

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. 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.

5

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.

2-4 HIGH VOLTAGE WARNING

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

25.0KV ± 1KV

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 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 10K 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.

6

3. OPERATING INSTRUCTIONS

This procedure gives you instructions for installing and using the 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:

15 - Pin Color Display Signal Cable

PIN NO.

DESCRIPTION

PIN NO.

DESCRIPTION

1.

RED

9.

5V From PC

2.

GREEN

10.

Sync GND

3.

BLUE

11.

NC

4.

GND

12.

SDA

5.

GND

13.

HORIZ. SYNC

6.

GND-R

14.

VERT. SYNC (＊VCLK)

7.

GND-G

15.

SCL (DDC CLOCK)

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.

6. If your color display requires service, it must be returned with the power cord.

1

6

11 15

5

10

7

4. ADJUSTMENT

4-1 ADJUSTMENT CONDITIONS AND PRECAUTIONS

4.1.1. Approximately 30 minutes should be allowed for warm up before proceeding.

4.1.2. 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. 14V ADJ PCB - MAIN VR903

2. B + ADJ PCB - MAIN VR902

3. SCREEN ADJ FLY BACK TRANS T402 SCREEN VR

4. FOCUS ADJ FLY BACK TRANS T402 FOCUS VR1&VR2

5. ABL ADJ PCB - MAIN AB in factory OSD

6. FUNCTION ADJ -MENU PCB - MAIN <SW104>

-UP

PCB - MAIN SW104

-DOWN

PCB - MAIN <SW103>

-EXIT PCB - MAIN SW103

-RECALL PCB - MAIN (SW103)

4-3 ADJUSTMENT METHOD

4.3.1. 14V, B + & HV voltage adjustment:

A. Chroma-2000 Signal generator or PC equivalent set mode 1, VGA 640X480 pattern 1.0.
B. Connect a DC Volt meter between TP901 and ground, then adjust VR903to be 14VDC.
C. Connect a DC Volt meter between TP902 and ground, then adjust VR902 to be 64 VDC.

4.3.2. 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 its value for the optimum picture.

8

CONTRAST

H-MOIRE REDUCE

BRIGHTNESS

V-MOIRE REDUCE

H-CENTER

R-GAIN

H-SIZE

G-GAIN

V-CENTER

B-GAIN

V-SIZE

R-BIAS

Tm

BURN IN TIME

G-BIAS

PINCUSHION

R-BIAS

TRAPEZOID

DEGAUSS

PIN-BALANCE

OSD EXIT

PARALLELOGRAM

SH

OSD H-SIZE

ROTATION

DC

video ic dc off set

Top corner

V-LINEARITY

Bottom corner

FM

Frequency select

93

9300 COLOR TEMPERATURE

KY

Select four key or five key

65

6500 COLOR TEMPERATURE

HP

H-SIZE-PHASE

OH

OSD H-CENTER

OV

OSD V-CENTER

BI

SET BURN-IN

HL

H-Linearity Modify

HS

SUB-H-SIZE

SB

Brightness Select

SV

OSD V-SIZE

LH

Brightness Save

SAVE BURN IN GEO

Language select

AB

ABL

RETURN

VR

V-HV Variation rate ajust

HR

H-HV Variation rate ajust

Adjust the linearity of V-both sides to

center

9

D. To switches the input signal to the other Timing Mode. Please follow step C ~ D 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.

4.3.3. White Balance adjustment:

A. Choose key X of OSD and press it for above 10s,then enter into factory setting area for

modulation.

B. Brightness & contrast ratio MAX, fix to G-BIAS,fix to 47.
C. Raster Max modulation: Raster Pattern, adjust R or B bias and G2, make x=271, y+301,

Y=3.0±0.2 cd/m2

D. Raster cut off modulation: Raster Pattern, adjust brightness to make Cut off: 0.08±0.02

cd/m2,and then put 9300K & 6500K into it.

E. Choose 3 for LH,set R or G or B gain,make x=281, y=311，Y=260,then save it into 9300K color

temperature,set R or G or B gain, make x=313, y=329 Y=240,then save it into 6500K color
temperature,in the end exit the factory setting area.

F. Choose 2 for LH,set R or G or B gain,make x=281, y=311，Y=200,then save it into 9300K color

temperature,set R or G or B gain, make x=313, y=329 Y=180,then save it into 6500K color
temperature,in the end exit the factory setting area.

G. Choose 1 for LH,set R or G or B gain,make x=281, y=311，Y=140,then save it into 9300K color

temperature,set R or G or B gain, make x=313, y=329 Y=140,then save it into 6500K color
temperature,in the end exit the factory setting area.

H. Exit factory setting area, white screen appears, the brightness cuts off, adjust factory AB value,

make it 9300K, color temperature Y=95±1 cd/m2

I. After modulation, it’s necessary to check if the white balance accords with the normal
specification. If not, which needs reset.

4.3.5. 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.

10

RELATIVE PLACEMENT OF TYPICAL COMPONENTS

Purity Magnets

Deflection Yoke

4-pole Convergence Magnets

6-pole Convergence Magnets

4.3.6 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.

4.4 EDID CONTENTS

x0 x1 x2 x3 x4 x5 x6 x7 x8 x9 xA xB xC xD xE xF
00: 00 FF FF FF FF FF FF 00 05 E3 00 C7 * * * *
10: * * 01 03 68 20 18 78 2A 4F 29 A0 57 49 9B 26
20: 10 48 4C A4 42 00 31 59 45 59 61 59 81 80 01 01
30: 01 01 01 01 01 01 EA 24 00 60 41 00 28 30 30 60
40: 13 00 36 E6 10 00 00 1E F9 15 20 F8 30 58 1F 20
50: 20 40 13 00 36 E6 10 00 00 1E 00 00 00 FC 00 48
60: 54 37 30 30 0A 20 20 20 20 20 20 20 00 00 00 FD
70: 00 32 A0 1E 48 0B 00 0A 20 20 20 20 20 20 00 **

11

5. CIRCUIT DESCRIPTION

5-1 MICRO CONTROLLER CIRCUIT

MICRO Controller

The IC101 contains a 8031 8-bit CPU core, 60K bytes of RAM, 16K bytes of ROM,14 channel 8 bit
PWM D/A converters, 2 channel A/D converters for key detection,0.5sec watch-dog timer, internal H­sync 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. Pin41/Pin42 are for the H-SYNC
and V-SYNC input, Pin34/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 48KHz H-SYNC free run signal. for the monitor testing use.

5-2 DEFLECTION CIRCUIT

The deflection circuit is achieved by a high performance and efficient solution IC 401 (STV 9118) for
this monitor. The concept is fully DC controllable and can be used in applications with a micro­controller solutions.
The STV9118 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 the STV9118.

Horizontal Oscillator

The oscillator is of the relaxation type and requires a capacitor of 1nF C405 at pin29.

PLL 1 Phase Detector

The phase detector is a standard one using switched current sources. It compares the middle of H­sync. with a fixed point on the oscillator saw-tooth voltage. The PLL loop filter R411,C437,C435 is
connected to Pin9.

PLL2 Phase Detector

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 pin5.

X-ray Protection

12

The X-ray protection input pin25 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:

Vertical Oscillator

The vertical free –running frequency is determined by the resistor C610 at pin19. Usually the free­running frequency should be lower than the minimum trigger frequency.

5-3 TRANSISTOR & DIODE CIRCUIT

LOCATION

CIRCUIT FUNCTION DESCRIPTION

D901 ~ D904 Bridge Rectifier for AC Source
D910 Clamp Diode for Snubber CKT
D918, D919 Rectifier for Output Voltage
D922 Rectifier for Output Voltage
D923 Rectifier for Output Voltage
D925 Rectifier for B+ Supply
Q901 MOS FET for Switching Power Control.
Q907, Q908 Use for Off-Mode to Cut-off 6.3V Supply Voltage
Q909, Q918 Use for Standy-By or Suspend Mode to Cut-off 12V Supply Voltage
Q912, Q920 Push-Pull Topology to Drive Q911
Q913 Degaussing Switcher Transistor
Q921 5V Regulator Transistor
Q701 Turn-on at Power ON/OFF and Change Mode to Protect Hor.Block
Q402 HOR. Driver Transistor
Q426 Horizontal s correction control MOSFET
Q404, Q405 As Differential Amp. to Drive Q406
Q406 Transistor for H-Size Control
Q705 Brightness Control CKT

13

6.TROUBLE SHOOTING CHART

6-1 NO RASTER, CRT RELATIVE CIRCUIT PROBLEMS

REFER ITEM S.M.P.S.

BRIGHTNESS SET TO MAX.
CHECK CRT G1 VOLTAGE

N

G

NG N

G

NG N

G

O

KOK

O

K

O

KOK

CHECK THE HIGE VOLTAGE O F CR

T

ABOUT 24.5 ~ 25.5KV

CHECK THE VOLTAGE OF CR

T

HEA TER ABOUT 6.3V

CHECK VOLTAGE OF THE CRT

CHECK BRIGHTNESS CIRCUIT

OK

CHECK POWER SAVING CIRCUIT,
H-SYNC, V -SYNC SIGNAL
Q909, Q910

"ABNORMAL DISPLAY"

CHECK SCREEN VOLTAGE ABOUT

LESS THAN 300V

CHECK FBT

CHECK MAIN PCB POWER SUPPL

Y

55.5V, 12.3V, 6.3V

CHECK FAILSAFE CKT

CHECK CRT'S HEATER RELATIVE
CIRCUIT Q907, Q908

Q703, Q704, Q705 RELATIVE CKT.

PIN 25 RELATIVE CKT.

400V TO 600V

REFER ITEM 6-2

CATHODE ABOUT 55V TO 65V