Mitac 1766PD Service Manual

S

ervice Manual

Monitoare

MITAC.
MITAC.
MITAC.
MITAC.

General Partner

T

echnical worl

d

®

PC

1766PD.
L-1766PD.
M-1766PD.
M/L-1766PD.

1. FEATURES

This monitor specifically provides the following features:

Microprocessor-based design with digital control

Non-volatile memory for 10 factory preset and 10 user-defined timing modes

Built-in switching regulator power circuit, can be used with

50/60Hz universal power supply

Manual degaussing

Display rotation

True color adjustment (red-green-blue)

Full screen

Low electro-magnetic radiation emission (for

OSD (on-screen display) control function

Green machine (power saving):

L/AL,

model)

100-260V

AC,

3. ENVIRONMENTAL REQUIREMENTS

Temperature

O°C -

l ENCLOSED CABINET:

40°C (operating)

Humidity
. OPERATING:

. STORAGE:

Altitude
. OPERATING:

.

STORAGE:

-2OOC -

10 - 80%)

60°C (storage)

nOJl-COlldeJlSiJl~

10 - 90%, non-condensing

up to 10,000
up to

30,000 ft.

l-t.

BANDWlDTH

H FREQUENCY (KHz)
V FREQUENCY (Hz)

N/N1

(KHz)

50.000 44.908

48.077 35.528 48.363 55.843

72.188 86.972 60.004 69.979

NI

65

.ocu

I

74.161 11.016

NI NI

63.750

59.747

NI

H FRAME BORDER

H TOTAL SIZE (Its)

H DISPLAY SIZE

H REAR PORCH

H

SYNC WIDTH

H SYNC POLARITY

V FRAME BORDER
V TOTAL SIZE (ms)
V DISPLAY SIZE

V REAR PORCH

V SYNC WIDTH (ms)
V SYNC

POLARKY

*H: horizontal

(Its)

(111;)

(cts)

(11s)

(ms)

(ins)

(ms)

*V:

20.x00

lh.Ocx)

13.x53

12.480 IO.808

vertical

0

1.280

-__

2.400 3.919 2.092 2.373

+ +

0

0.478 0.563 0.600 0.537

0.125 0.113
+

0

28.146 20.677 17.907

22.802

1.1%

0 0 0

Il.498

t

0 0

15.754

2.462

16.666 14.290

IS.880

0.124

13.808

I.294

13.663

0.072

0

IS.686

Il.620

I.997

1.489

t

0

16.737

16.062

0.596

0.047

i

(continued)

This monitor also provides 10 blank storage areas for the control settings of each timing

mode. If you are not satisfied with the standard settings for a certain mode, you can

define your own settings following this procedure:

1.

Use

SELECT,/4

2.

Use ADJUST + I- to ad-just the value of that option.

3.

Press STATUS to save the settings.

(If you change the video mode while

\

the STATUS button before you can use the control

to select the option you want to

the OS11

is activated, you

acl_just.

panel

may

buttons.

have to

press)

I

6. THEORY OF OPERATION

Switch Mode Power Supply

The current mode control IC is

<J902.

To avoid the screen being interfered, its circuit

applies SYNC trigger.

Pin 6 of

U902

directly drives

JviIOSFET Q901

and oscillates

T901

transformer,
so that energy will be transferred from the primary voltage to the secondary volt­age . The secondary voltage is rectified by D912, D913,

D914

and

D916,

tain output voltage by way of the n filter circuit.
Pin 3 of
T901 via R919. Via pin 2 of 17902, the feedback of

U902

offers over current protection, which detects the source current of

U903

rectifies the output
voltage from pin 3 of R9 19.
TH801 is a positive temperature coefficient resistance. It performs degaussing
function when the power is on.
The power saving circuit consists of C927, Q902, Q903, Q908, R928, R929,
R942,
on pin 1 of

R951,

and

U908.

If the vertical SYNC signal doesn’t appear, the voltage

U902

will shut down, and the SMPS (Switch Mode Power Supply)

will be OFF.

See figure SD640012120021 - 1 of 3 (page 35).

to ob-

Input Circuit

From the SYNC signal of U 101, we know

the

shaping and polarity status. We also get
positive horizontal SYNC output from pin 6, and positive vertical SYNC output from
pin 8.

In order to make sure that the horizontal SYNC output and vertical SYNC output have

the same pulse width, we use U 102.

See figure SD640012120021

- 3

of 3 (page

35).

Horizontal Driver Circuit

The output point of the horizontal driver pulse is pin 8 of

U305.

T.501 increases the horizontal driver pulse current to drive Q.504.
B+ parabolic wave flows into

C.506, C507, C508

are controlled by

L401

to modify a

Q505

and

pinchushion.

(2506

to get the horizontal linear­ity .

L501

is a variable horizontal linearity coil.

See figure SD640012120021 - 3 of 3 (page 35).

High Voltage Driver Circuit

This is a diode modulation circuit. The horizontal deflection and the high volt­age are integrated together.
The tunning capacitors C5 12 and C5 14, which are controlled by

RI>501

,

used to keep the high voltage.

FBT generates 24KV,

See figure SD640012120021 - 3 of 3 (page

-17OV

and the feedback signal.

35)

are

Step-down B + Circuit

l

U801

is adopted to be a monostable circuit, triggered by pin 4 of FBT. The

square wave comes out from pin 3 of

l

C.517,

D802,

L802,

and QS 10 generate the step-down

U801.

See figure SD640012120021 - 3 of 3 (page 35).

Double Focus Circuit

l

U402

generates the vertical parabolic wave.

l

L603, C611

l The

hrizontal

and C613 generate the horizontal parabolic wave.

and vertical parabolic waves are integrated by

to pin 11 of FBT.

See figure SD640012

12002

1 - 3 of 3 (page 35).

R+.

T601

and then sent

OSD Microprocessor Circuit

The

84C882

For

84C882,

The
The vertical SYNC goes through

is a

g-bit

microprossor. The PCF8582 is the EPROM.

FB/GO/BO/RO signal comes from pin

pirt

5.

1,

2,

3,

?

4.

The horizontal SYNC goes through pin 6 and pin 11.

PWM signal comes from pin 9, 24, 25, 26, 27,

The

28, 29,

37,

and 38.

Pin 33 provides the RESET function.

frequency detection signals come

The

When pin 19 is under the “active low”

from

pin 13,

14,

mode, it provides the MUTE function.

15,

16,

17, 18.

When pin 20 is under the “active high” mode, it provides the DEGAUSSING

function.

See figure SD6400 12 12002

Video Amplifier Circuit

LM1207 is a

l The R/G/B signal goes through pin 4, 6, 9.
l The R/G/B signal comes from pin 26, 20, 17.
l The R/G/B gain is controlled by pin 28, 18,
l The R/G/B bias is controlled by pin 27, 19, 16.
l The negative clamp pulse comes from pin 14.
l The contrast DC level is controlled by pin 12.
l The R/G/B video output cascade circuit consists of

R711,

l The SEPP (Single End Push Pull) circuit consists of

85MHz

R7 12,

pre-amplifier IC.

R705,

R706, and

1 -

2 of 3 (page

C704.

35)

_

15.

Q701,

Q507

used to increase the video bandwidth for the K/G/B video output.

See figure SD640012 120023 (page 35).

Q702,

and

Q504,

D701, L701,

which is

6.

Geornetic Adjustment

input timing:

_

input pattern:
test point:

ail

timings

_crosshatch

pis~cushioll/h~~~,I-cl,

t

rapczoid

and + I- buttons

test value:

7. Tile Adjust

input timing:
input

test

rnent

pal

tern: crosshatch

value:

ADJ VK: rotate VR

8. Dark

Balarlcc

Adjustrl~erlt

input timing:
input pattern: raster
test point:

xl:

0.2111111, y’ 0. 1Jntn

dl

1illiiIlgS

I

2.5nllll

31KHz

brightness =maximum (external

conk01

panel)
contrast =maxinliun (external control panel)

VR70.1,

VR704,

VI1705

= maximum

test value:

VR703

VR704

VR7OS

YI I .OF.L.

-

-

-

x

=28 1225
y=311rm
y=3l l-t25
x=281k25