Samsung CC9511 User manual

c8 SAlUlSUNG
SERVICE MANU- AL
19" COLOR MONITOR
MODEL:CC95"t1

CONTENTS
IMPORTANT SERVICE SAFETY PRECAUTIONS ........................................ 3
ENGINEERING SPECIFICATIONS
....................................................... 5
THEORY OF OPERATION
1. Line input ......................................................................... 10
2. Power supply ....................................................................... 10
3. Horizontal ......................................................................... 11
4. Vertical deflection .................................................................. 15
5. Sync. processing .................................................................... 16
6. Video ............................................................................. 17
7. Tube biasing ....................................................................... 18
DISASSEMBLY INSTRUCTIONS ......................................................... 19
BLOCK DIAGRAM ...................................................................... 21
ADJUSTMENTS ON INSTALLATION
Howto adjust ........................................................................ 23
ALIGNMENT INSTRUCTIONS
1. B+ Adjustment .................................................................... 28
2. Horizontal frequency adjustment ...................................................... 28
3. Horizontal PhaseAdjustment ......................................................... 28
4. Vertical frequency adjustment ........................................................ 28
5. Focus adjustment ............................................................•. · ...... 28
6. Side pincushion adjustment ........................................................... 28
7. Horizontal linearity adjustment ....................................................... 28
8. Vertical linearity adjustment ......................................................... 28
9. Horizontal centering adjustment ...................................................... 28
10. Vertical centering adjustment ..............................•........................ 28
11. Width adjustment .................................................................. 28
12. Vertical size adjustment ............................................................ 28
13. Color purity adjustment ............................................................. 29
14. Screen adjustment ................................................................. 29
1

15. White balance adjustment ........................................................... 30
16. Static (center) convergence ........................................................... 30
17. Dynamic convergence ..................................... : ........................ 31
TROUBLE SHOOTING GUIDE .......................................................... 32
WIRING DIAGRAM AND PARTS LOCATION ........................................... 37
PRINTED CIRCUIT BOARDS
1. Power PCB ( TOP view) ............................................................. 39
Power PCB ( BOTTOM view) ........................................................ 40
2. Deflection PCB (TOP view) ........................................................ .41
Deflection PCB ( BOTTOM view) ................................................... .42
3. Video PCB ( TOP view) ............................................................. 43
Video PCB (BOTTOM view) ...................................................... .44
4. CRT PCB( TOP and BOTTOM view) ................................................ .45
5. HN Regulation Module PCB ( TOP and BOTTOM view) ............................... 46
6. Output TR PCB ( TOP and BOTTOM view) .......................................... 46
7. Stand PCB (TOP and BOTTOM view) .............................................. .47
8. LED PCB ( TOP and BOTTOM view) ................................................ 47
9. FBT PCB (TOP and BOTTOM view) .................................................. 48
CABINET EXPLODED VIEW / PARTS LIST
1. Cabinet exploded view .............................................................. 49
2. Cabinet parts list .................................................................... 51
3. ·Electrical parts list .................................................................. 54
SCHEMATIC DIAGRAM ................................................................ 75
WAVEFORMS· .......................................................................... 84
SEMICONDUCTOR LEADS IDENTIFICATION ........................................... 86
2

IMPORTANT SERVICE SAFETY PRECAUTION
Service work should be performed only by qualified service technicians who are thoroughly familiar with all
of the following safety checks and servicing guidelines.
WARNING
1. For continued safety, do not attempt to modify
the circuit.
2. Disconnect the AC power before servicing.
3. Semiconductor heat sinks are potential shock
hazards when the chassis is operating.
SERVICING THE HIGH VOLTAGE SYSTEM
AND
PICTURE TUBE
When servicing the· high voltage system, remove the
static charge by connecting a 20kohm resistor in
series with an insulated wire(such as a test probe)
between the chassis and the anode lead. (The AC
line cord should
be disconnected from the AC out-
let.)
1. The picture tube in this display monitor employs
integral implosion protection.
2. Replace with a tube of the same type and num-
ber for continued safety.
3.
Do not lift the picture tube by the neck.
4. Handle the picture tube only when wearing shat-
ter proof goggles and after discharging the high
voltage anode completely.
X-RADIATION AND HIGH VOLTAGE LIMITS
1. Be sure all service personnel are aware of the
procedures and instructions covering X-radiation.
The only potential source
of X-ray in a current
solid state display monitor
is the tube. How-
ever,the picture tube does not emit measurable
X-ray radiation
if the high voltage is as specified
in the "high voltage check" instruction.
3
It is only when high voltage is excessive that X-
radiation is capable of penetrating the shell of
the picture tube,including the lead in glass
material. The important precaution is to keep the
high voltage below the maximum level specified.
2. It is essential that serviceman have available at
all times an accurate high voltage meter. The
calibration
of this meter should be checked pe-
riodically.
3. High voltage should always
be kept at the rated
value -no higher. Operation at high voltages may
cause a failure
of the picture tube or high voltage
circuitry and,also under certain conditions,may
produce radiation in excess
of desirable levels.
4. When the high voltage regulator is operating
properly there
is no possibility of an X-radiation
problem.
Every time a color chassis
is serviced,the bright-
ness should4
be tested while monitoring the high
voltage with a meter to
be certain that the high
voltage does not exceed the specified value and
that it is regulating correctly.
5.
Do not use a picture tube other than that
specified or make unrecommended circuit
modifications to the high voltage circuitry.
6. When troubleshooting and taking test measure-
ments on a display monitor with excessively high
voltage, avoid being unnecessarily close to the
display monitor.
Do not operate the display
monitor longer than
is necessary to locate the
cause of excessive voltage.
BEFORE RETURNING THE DISPLAY MONITOR
Fire and Shock Hazard
Before returning the display monitor to the user,per-
form the following safety checks:

1. Inspect all lead dress to make certain that the
leads
are not pinched or that hardware is not
lodged between the chassis
and other metal parts
in the display monitor.
2. Inspect all protective devices such as nonmetallic
control knobs, insulating materials, cabinet backs,
adjustment and compartment covers or
shields,isolation resistor-capacitor net-
works,mechanical insulators,etc.
3.
To be sure that. no shock hazard exists, check
for leakage current in the following manner:
• Plug the AC line cord directly into a 12Ovolt AC
outlet. (Do not use an isolation transformer for
this test)
• Using two clip leads,connect 1.5 kohm,lO watt
resistor paralleled by a 1.5uF capacitor in series
with all exposed metal cabinet parts and a known
earth ground, such as electrical conduit or
electrical ground connected
t~ earth ground.
• Use a SSVM or YOM with 1000 ohms per-volt
or higher sensitivity to measure the AC voltage
drop across the resistor.(See Figure 1.)
• Connect the resistor to all exposed metal parts
having a return path to the chassis (metal cabinet,
screw heads, knobs and shafts, escutcheon, etc.)
and measure the AC voltage drop across the
resistor.
• Any reading of O.3volt RMS (this corresponds to
O.5milliamp.AC) or more is excessive and
indicates a potential shock hazard which must
be
corrected before returning the display monitor to
the user.
SAFElY NOTICE
Many electrical and mechanical parts in this chassis
have special characteristics often pass unnoticed and
the protection afforded by them can not necessarily
be obtained by using replacement components rated
for higher voltage,wattage,etc.
Replacement parts that have these special safety char-
acteristics are identified in this manual,and its supple-
ment electrical components having such features are
4
AC
VOLll£TER
1500 0
TO EXPOSED
~AL PARTS
TO KNOWEN
EARTH GROlN)
Figure 1. Leakage Current Test Circuit
identified by
a& in the Parts List and Schematic
diagrams.
Before replacing any of these components,read the
Parts List in this manual carefully. The use of sub-
stitute replacement parts that do not have the same
safety characteristics as specified in the Parts List
may create shock, fire, or other hazards.

ENGINEERING
1. DESCRIYrION
This specification describes in detail, the electri-
cal and mechanical performance of a 20-inch color
monitor. This monitor
is designed to work with the
CAD/CAM workstation or PC(personal computer).
The monitor will accept RGB analog video output of
the computer and display this information in up to
infinite color renditions. Monitor syncronization
is
controlled by a sync on green video or any polarity
separate
TTL sync or composite TTL sync. All
parameters shall be met within the limits specified in
this
document unless otherwise specified. The
specification is subject to change without notice.
2. MECHANICAL DESCRIPTION
2.1 Dimension
525(L) x 484(W) x 488(H) mm : Net
622(L) x 558(W) x 559(H) mm : Gross
2.2 Weight
35 Kg
37 Kg Net
Gross
3. POWER INPUT SPECIFICATIONS
3.1 Input Voltage
120V range : AC 90 - 132 volts.
220V range : AC 198 -264 volts.
3.2
Input Frequency
50 ±3 Hz or 60 ±3 Hz
4. SIGNAL INPUT SPECIFICATIONS
4.1 Signal Wave Form
Signal input
is based upon EIA standard
RS343.
4.2 Video Signal
a)Type R(Red),G( Green),B(Blue)
analogtype
(Composite SYNC signal will be taken from
the Green video signal.)
b) Level
Composite
Non-composite
c) Signal polarity
d) Impedance
:
1.0 Vp_
p Norminal
: 0.7 Vp_
p Norminal
Positive bright
5
SPECIFICATIONS
Terminated
75 ohms 2%
Unterminated: Greater than 10 Kohms
switch selectable.
4.3 Sync Signal
a) Type
Composite sync on Green or composite H/V
sync or seperate
H/V sync are automatically
selectable.
b) Level
Composite : SYNC to total signal ratio
= 28.6 5%
External : DC coupled TTL level
( separate
H/V sync and composite H/V sync.)
c) Signal polarity: Positive or negative.
4.4 Sync Frequency
a) Horizontal :
46-52KHz (50 KHz version)
52-58KHz
58-64KHz (64 KHz version)
b) Vertical 55-65Hz non-interlaced
4.5 Input Connector
BNC type receptacle for each
RG.B video
signals and external SYNC signals.
4.6 Signal Timing : see timing chart (page 9)
5. CRT SPECIFICATIONS
Parts NO
Type
Mask Pitch
Phosphor
Transmission
Face
E8111 B22
ET AR or
M48JLK22X
20" 90 DEGREES, 29MMO,
SELF-CONVERGENCE
0.31mm
RG.B, Medium Short
Persistance
Approx.70%
AR Panel
6. RESOLUTION
1280 dots x 1024 lines ( 64 KHz version )
1024 dots x 768 lines ( 50 KHz version )
7. ENVIRONMENT
7.1 Operating Environment
a) Temp 0 -
4QoC

b) Humidity
c) Altitude
10. -90%
3000m max.
7.2 Storage and Shipment Environment
a) Temp -30 -+ 6SoC
b) Humidity 10 -90%
c) Altitude 12,000m max.
7.3 Vibration (Package Condition)
a) Frequency TBD
b) Vertical TBD
c) Horizontal TBD
7.4 Shock
1 corner, 3 edges and 6 surfaces
8. ELECTRICAL PERFORMANCE
8.1 Testing Conditions
All tests must be perfomed under "Standard
Testing Condition " except where otherwise
noted.
" Standard Testing Condition " is defined as:
a) AC Supply Voltage 120VAC, 60Hz
b) Ambient Temperature 20. SoC
c) Brightness Control Center Click
d) Contrast Control Set to maximum
video gain
e) View Direction
Parallel to the CRT axis
The set shall be tested with facing to
North-east.
f)Magnetic Field: 0.03m telsa steady state
in any orientation.
g) Thermal Stablization
After 20 minutes from the time AC power
has been applied.
8.2 Power Supply
Input Current : 2.5A max.
Power Consumption
8.3 Video Output
8.3.1 Band Width
(120VAC / 60Hz)
140W max.
SOHz to 100MHz ( 3DB ) - 64KHz version
SOHz to 70MHz ( 3DB ) - SOKHz version
* Amplifier response shall be less than 3dB
down at 100MHz (70MHz) as referenced to
SOHz and with 20 volts of drive to the CRT.
6
8.3.2 Rise / Fall time
S.Onsec max. -64KHz version
6.0nsec max. - SOKHz version
8.3.3 Video Amplifier Differential Gain
Less than S% for 30 volts p_p of video at
the CRT.
8.3.4 Black Level Stability
Black level shift to be less than 1% of peak
luminance from 10% to 90% average picture
level.
8.3.5 Contrast Control Range
Shall provide a minimum of 7dB of adjustment
range from minimum to maximum setting.
8.4 Image
8.4.1 Image Size
Horizontal : 360 ± Smm
Vertical : 270 ± Smm
8.4.2 Image Centering
Edge of bezel opening
A
G
Display area
IA-BI s 4mm
IC-DI S 3mm
8.4.3 Geometry
D
Trapezoid / Parallelogram
EF - GH
----- x 100 s 1 % max.
EF + GH (horizontal)
EG - FH
----- x 100 s 1 % max.
EG + FH (vertical)
F
B
H

Pincushion /
Horizontal:S 4 mm max. (A,B)
Vertical
:S 3.4 mm max. (C,D)
Rotation : 1.0% max
8.4.4 Linearity
The linearity will
be measured by means of
full screen cross hatch pattern.
The pattern to be white lines on a black
background.
Linearity to
be calculated as follows
MAX -MIN x 100
:s 5 % max.
MAX + MIN
MAX
MIN
Maximum square size.
Minimum square size.
8.5 Overall Performance
8.5.1 Mis-convergence
Convergence shall not deviate more than
O.3mm in a central area bound by a circle.
The diameter
of this circle is 260mm.
Elsewhere, deviation shall not exceed O.5mm.
360mm
1 ___ ' ---~'I-
270mm
B
Center area of display (A) : O.3mm max.
Peripheral area
of display (B) : O.5mm max.
8.5.2 Luminance
a) Maximum Luminance :
No less than
30 foot lambert.
b) Uniformity
No less than 60% of peak luminance.
7
8.5.3 White Coordinate
The reference white shall
be that of the black
body at temperature of 9,300 degrees K. C.I.E.
coordinates are X = 0.281, Y = 0.311.
Coordinate to be whitin .03 when measured
at 5 foot lambert light output settings.
Coordinate to
be whitin .02 when measured
at
20 foot lambert light output settings.
At 20Ff-L Luminance: X=0.281 ± 0.02
Y = 0.311 ± 0.02
At 5 Ff-L Luminance: X=0.281 ± 0.03
Y = 0.311 ± 0.03
8.5.4 Purity
Conspicuous miss-landing shall not
be visible
within display area at distance of
60 cm from
CRT surface at
15 foot lambert white
luminance.
8.5.5
Jitter
Less than 1 dot, or invisible at distance of
60 cm from CRT surface.
8.5.6 Dispaly regulation
Due to brightness variation :
Within 1% of display size.
Due to power supply variation :
Within
1% of display size.
Due to temperature variation :
Within
2% of display size.
9. AUTOMATIC DEGAUSSING
Automatic degaussing of the CRT to be
provided at switch on.
10. APPLICABLE DOCUMENTS
UL 478 : Standard for safety. information-
processing and business equipment.
CSA C22.2 :Data processing equipment.
FCC RULES
PART Class A computing devices
IS SUBPART J
DHHS RULE 21
X-ray emissions.

SUBCHAPTER J
VDE 0806 : Safety Specification for business
machine
VDE0871 Regulation for the radio frequency
interference suppressions of high
frequency apparatus and installations,
class A computing equipment ref.
0871/6.78
PTB : German X-ray decree of march,
1973
IEC380 : Safety of office appliances.
IEC435 : Safety of data processing equipment.
BS5850 : Britith standards institute standard for
office machines.
11. Applicable Signal Timing Chart.
8

Video input signal timing chart (Standard timing)
(1) HN COMPOSITE SYNC.
R.G.B signal (analog)
VIDEO
(R.G.B)
_ ____
H-SYNC.
"-
(HORIZONTAL)
12.075
DISPLAY TIME
~ -
V-SYNC.
(VERTICAL)
1024H
DISPLAY TIME
0,415 I_I 1.774
-N 1.1 2Q!I
1.434
3H
15.698 --~
(unit :uS)
1---1060H -~
(2) SYNc. ON GREEN
Green signal
(HORIZONTAL) I I+----- 12.075 . I I
UI DISPLAY TIME L.J
0,415 . I_I 1.774
1.434
+----- 15.698 -----+1
(unit: uS)
(VERTICAL) ~.
1024HH---------+· I I
DISPLAY TIME ~
~U
30H
+------ 1060H ----I
(unit: H)
9
(unit :H)

THEORY
1. LINE INPUT
The input rectifier section converts the AC line
voltage into a crudely filtered
and unregulated DC
voltage, powering the switching regulator. The input
section is a full-wave bridge.
1.1.
FILTER
To reduce noise from the power supply, a low-pass
filter isolates
the switcher. The conducted noise is
filtered by X
and Y capacitors and a common mode
transformer.
2.
POWER SUPPLY
The design uses a discontinuous flyback topology
operating in current-mode resulting in a multiple
output switcher with outputs which track well.
There
are no output filter chokes. Slower diodes are used.
The fast transient response of the control loop
maintains picture integrity. Very fast current limiting
protects
the switcher against short circuits.
2.1. P.W.M. INTEGRATED CIRCUIT
The 3842 is an integrated current mode pulse width
modulator.
It consists of an oscillator, error
amplifier, current sense comparator, under-voltage
lockout,
and an output MOSFET driver stage.
2.2. UNDER-VOLTAGE
LOCKOUT
This circuit insures that Vcc is adequate to make
the 3842 fully operational before enabling the
oscillator, voltage reference,
and before turning on
the
output stage. The turn-on/off thresholds are at
l6v and lOv respectively.
2.3. OSCILLATOR
The oscillator consists of a pull up resistor from the
Sv reference to pin 4 of IC601 and a timing capacitor
to ground.
When the voltage ramps up to about 2.8v
OF
10
OPERATION
on pin 4 of IC601 an internal current source pulls
down, discharging the
timing capacitor to a l.Ov level.
This level releases the current source
and starts the
next cycle. Oscillator frequency is roughly equal to
l/.5SRC.
Synchronization is achieved by feeding timing pulses
from a reference into the oscillator.
2.4. OUTPUT STAGE
The 3842 has a single totem-pole output capable of
operating
to l.0 A peaks and a 200mA average cur
rent.
2.5. CURRENT SENSE COMPARATOR
Current-mode controllers inherently keep close
watch over
the pass transistor's current. Pin 3 of
IC601 is connected to a voltage comparator which
shuts off the output when
current reaches the desired
level, as prescribed by
the error amplifier. This way
the controller will only allow the
needed amount of
power into the output transformer. This method
differs from most pulse width controllers which
compare the error amplifier's output against the
oscillator's voltage ramp. This results in control of
on-time, which does not necessarily mirror
the power
stored in the transformer.
This
comparator also serves the dual purpose of
monitoring
current limit. Any time pin 3 of IC601
rises above 1 volt the output will terminate.
Output -short circuits and core saturations are
detected before they destroy
the pass transistor.
2.6.
ERROR AMPLIFIER
Voltage on pin 2 of IC601 is compared with a 2.Sv,
2% source. Errors in output voltage are amplified
and fed to pin 1 of IC601 where they are frequency
compensated by an
RC back to pin 2 of IC60l. This
error voltage is dropped by l.4v and divided by 3
before being fed
to the current comparator.
In this application, the error amplifier is on the
secondary side
of the switcher. Inside the

IC604(TlA31), T603 in the data book, is a
programmable reference. In side it consists
of a
temperature compensated reference and an amplifier.
Any error in output voltage is compared against
2.5
volts and amplified. Frequency compensation is
handled by C610.
Error current passes through an
optocoupler to another error amplifier.
2.7. Vee
The 3842 draws very little current in start up mode.
There is enough power from the line bleeder R604
to slowly charge C616
to the 16 volts needed to start
the switcher. When switching begins the Vcc falls
quickly
but before it drops to the 10 volt turn off
level, the horizontal section
of the monitor should be
up and running. A few turns of wire from around
the flyback transformer supplies power and
synchronization.
2.8. POWER TRANSFORMER
Transistor 0601 starts a cycle by allowing current to
flow into the primary
of T601. As current ramps up
with time, the voltage across current sense resistor
R608 also ramps to a point where IC601 determines
enough power is stored and turns off 0601. As the
voltage on
0601 flies upward, power is dumped from
the main power transformer through diodes in to the
different supplies. D602 clamps ringing which could
over-voltage 0601. A sample
of this voltage is fed
back to the optocoupler
to keep the power PET safe
encase
of a catastrophic failure.
To keep radio frequency radiation to a minimum
and reduce transistor heating, a turn-off snubber
network is placed across 0601.
The transformer has
a center leg gap with no gap in the outer legs. This
greatly reduces the flux radiating from the cores.
There also may
be a large copper strap around T601
to stray
flux.
2.9. RECTIFICATION and FILTERS
Currents from the secondary windings are rectified
and filtered to create the desired voltages. Low
internalseries resistance electrolytic capacitors reduce
ripple voltage.
Small high current capacitors quickly
return charging current
to the source.
11
3. HORIZONTAL
The next diagram shows a positive and a negative
horizontal section.
This monitor uses
the negative approach in the
horizontal section.
• +
3.1. PHASE·LOCK LOOP
A phase-locked loop synchronizes the horizontal
switch
to the timing pulses from the computer. The
phase-lock loop compensates for storage delay in
0401.
Incoming horizontal sync is level-translated by 0401
. then fed into the input of the phase comparator.
Transistor
0407 watches the falling edge of the
flyback pulse. When. the flyback pulse falls to within
a few volts of ground, a rising edge is sent
to the
other input of the phase-lock loop phase comparator.
The phase comparator operates in an edge lock
mode. Integrated circuit IC401(
4046) pin 13 is in a
high impedance mode most of the time. If the rising
edges fed into pins 3
and 14 of IC401 do not
coincide, pin 13
of IC401 goes into a low impedance
state for the time difference. Depending
on which
edge leads the other, current flows into
or is pulled
out
of the filter capacitors C408 and C409.
Voltage controlled oscillator input pin 9 of IC401
determines the frequency and phase
of the output
square wave on pin 4
of IC401 The free running
frequency and lock range is set by C406, R411, R412
and VR401.

diagraml.
If no sync is present the PLL will normally drop to
the bottom of the lock range. This causes problems
in setting the Horizontal Hold control.
One way of setting the H. Hold VR is to send video
into the monitor without H. sync (unplug the green
channel and the H. sync cable
if any). Adjust H.
Hold for a nearly stable picture. This should insure
that the free running frequency
is close to the
incoming sync frequency.
3.2. MISSING
SYNC
When the PLL does not see sync it tries to lower
the frequency of the monitor. With some types of
composite
sync, during vertical sync, where will be no
horizontal sync. The PLL
will drop the horizontal
frequency down a long way during the 3 to 4 missing
syncs.
The figure below shows how the input of the voltage
controls oscillator (pin 9 of IC401) drops with only
one missing
sync. Trace A represents the input of
the PLL that
is watching the flyback pulse. Trace B
is horizontal sync with one pulse missing. Trace C
comes from pin 1
of the PLL(IC401) and indicates
when an error condition arrives. Trace D
is the
input of the voltage controlled oscillator. Notice how
much the voltage drops in one line time and that the
recovery
is very slow.
12
Trace E shows how the missing sync c.ircuit adds in
the missing pulse. The pulse is late by about IuS
which is fare better that being one to five line times
late. Notice trace G, the input to the VCO, drops
very little. The PLL is back on frequency within a
few lines. Trace F is pin 1 of the PLL(IC401). The
time delay in the missing sync circuit is set by a RC
time constant. The voltage in the timing capacitor
is
seen in trace G.
diagram
2.
If a sync pulse is missing pin 1 of the PLL(IC401)
falls. After a time delay set
by R415, C410 the
missing pulse
is added by 0201. The missing pulse
circuit
is disabled by 0404 if many pulses are missing.
This condition usually arises because the sync
is
totally gone.
3.3. DOUBLE
SYNC
Refer to the sections MISSING SYNC and PLL to
understand the phase lock loop and what happens
when phase error
is detected.
If double sync is sent to the PLL the horizontal
frequency
will be driven up just like no sync drove
the frequency down. A diode(D403) and
transistor(0415)
is added from pin 4 to pin 14 of the
PLL(IC401) to short out any sync pulses that might
arrive during the half of the line time when
sync

should normally not be. For the half if the line that
includes blanking the sync is allowed to pass.
3.4. BASE DRIVE
When turned on, transistor
0410 turns off the
horizontal switch 0409.
At the same time, current is
stored on transformer T40l. When
0410 opens up
this stored power supplies turn-on current for 0409.
Resistor R442 sets the average power level to the
base drive circuit. Snubbing circuits surround
transformer T40l. They control the discharge current
waveform into the base.
3.5.
BASE DRIVE RESISTOR
The base drive resistor determines the amount of
base drive. If the transistor is over driven the Vset
looks very good, but the current fall time is poor. If
the base current is too small the current fall time is
very fast.
The problem is that the transistor will have
many volts across C-E when closed.
The best condition is found by placing the transistor
in the heaviest load condition. Adjust the base
resistor for the
least power consumption.
diagram 3.
3.6. CHOPPER
The horizontal section does not have a horizontal
power supply voltage like most monitors. A chopper
is used to take the 150 volt video supply and create
the necessary power for the horizontal section.
The
duty cycle of the chopper is controlled by a pulse
width modulator (PWM) IC40l.
The PWM watches
the current in the horizontal yoke and adjusts the
duty cycle to obtain the desired width.
13
Yoke current can be measured in several different
ways. The yoke current is directly related to the
voltage across the S capacitor, the average voltage
from the chopper and the peak flyback voltage.
The flyback pulse is upside down for the PWM. A
capacitor
and diode is used to invert the flyback
pulse. A resistor divider drops the 1200 volt flyback
pulse to 2.5 volts for the PWM.
3.7. HORIZONTAL SWITCH/DAMPER
DIODE
On the right hand side of the screen, transistor
0409 conducts current through the deflection yoke.
This current comes from the
"S" correction capacitor,
C433, which has a charge equal
to the supply voltage.
Diode D415 allows current for the left
hand side of
the screen to flow back through the deflection yoke
to C433.
3.8. FLYBACK CAPACITOR
The flyback capacitor connects the hot side of the
yoke to B+. This component determines the size
and length
of the flyback pulse. Choose the flyback
capacitor to adjust the second anode voltage.
Capacitors C431 must
be precision high voltage high
current components.
3.9.
"SO CAPACITOR
Capacitor C415 corrects outside versus center
linearity in the horizontal scan. The voltage on
The
S cap has a parabola plus the DC horizontal supply.
Reducing the value of S cap increases this parabola
thus reducing the size of the outside characters and
increasing the size of the center characters.
3.10. HORIZONTAL LINEARITY
In the yoke current
path there is a saturable coil.
Just like a size coil, any inductance in series with the
yoke will reduce the size of the picture. This
saturable coil will change inductance depending on
the amplitude and direction of current flow.
At the
start of a trace the linearity coil has an inductance
of
20 percent of that of the yoke. By the center of
the trace, the linearity inductance has decreased to
about 4 percent
of the yoke where it remains for the

rest of the trace. Adjust this variable inductor so the
right and left sides
of the picture are the same size.
3.11. HORIZONTAL
DC CENTERING
In the horizontal section
of
a monitor the yoke has DC
on the cold end and a
flyback pulse
on the hot side.
The current ramps in a
sawtooth fashion center
around zero.
If a parallel
coil is
added the current
through the yoke
is not
effected.
With the addition of a
battery and limiting resistor
the
DC current is added to
the current ramp. A plus
and minus supply gives full
control of the
DC offset
current.
The batteries or power
sources are created off a
small secondary winding
turning the parallel coil into
a transformer.
The final
circuit has no
AC effect on
the yoke but can cause a
+ /- current flow through the
yoke.
180uH YOKE
.iffffJiiii-
2 to 20MH COIL
RES. BAT.
~~
-f ~ :cr+
3.12. FLYBACK TRANSFORMER
The flyback transformer is separate from the
horizontal section. This
is done to allow greater
14
flexibility when changing frequency and tube size. A
small independent 'horizontal' section powers the
flyback transformer and creates the high voltage.
3.13.
X-RAY SHUT DOWN
When a fault in the high voltage section is detected
the horizontal base drives are shut down.
An over
current condition in the high volt supply or an
overvoltage condition
will trip a TlA31(IC405)1
2N2907(Q413,Q414) latch. Turning off the power
resets the latch.
3.14. TUBE BIAS SUPPLIES
Focus and G2 supplies come from a bleeder located
in the flyback transformer.
3.15. FOCUS
The focus voltage is obtained form the flyback
transformer. There
is no focus modulation used in
this color monitor.
3.16. MASTER BRIGHTNESS
The G2 voltage comes from the flyback transformer.
3.17. HIGH VOLTAGE REGULATOR
The patented high voltage regulator sits between the
supply and the top of the primary of the flyback
transformer.
An onboard switching regulator is
powered from the 17 volt supply. The regulator
watches the second anode voltage through a 300-mega
Ohm resistor in the flyback transformer. During
flyback, the regulator pulls the top
of the flyback
transformer negative while the flyback pulse
is raising
the other end.
In this way the size of the pulse, as
seen by the flyback transformer,
is varied to keep the
second anode voltage constant independent of load.
The regulator should be adjusted by "high voltage
adjustment" to the desired high voltage.

4. VERTICAL DEFLECTION
The TDA 1670(IC301) incorporates all the
necessary functions for providing the yoke of a
monitor or television receiver with the current
required for vertical deflection. Incorporated in
silicon
is a synchronizable oscillator, ramp generator,
voltage regulator, voltage doubler and power
amplifier.
4.1. VERTICAL OSCILLATOR
The oscillator is an integrator (pins 4 to 3 of IC301)
and a two threshold comparator which switches pin
6 of IC301 high or low to allow the charging of
C303.
D301 allows the charge and discharge ramps to have
adjustable slopes. Vertical sync pulses come in on
pin 5 of IC30l0
The
V. Hold VR sets the oscillator frequency.
4.2. RAMP GENERATOR
The ramp generator is made up of a current
generator, controlled
by current in pin 7 of IC301,
and the capacitor from pin 9 of IC301 to ground.
The slope, and thus the size of the linear ramp,
is
adjustable by setting the current pulled from pin 7 of
IC301 This ramp also appears buffered on pin
10
of IC301 at a much lower impedance.
4.3. VERTICAL POWER AMPLIFIER
A power amplifier, with input on pin 12 of IC301,
compares the ramp on pin 10 of IC301 to the current
ramp through the yoke. R308 and
C307 stabilize the
high gain power amplifier. Yoke current
flows from
pin 1 of IC301, through the yoke, the DC blocking
capacitor and a current sampling resistor to ground.
Voltage which represents yoke current
is then fed
back to the input of the amplifier to be compared
with the reference ramp
The output stage of the power amplifier
is supplied
by the 25 volt supply during a trace, and by the
vertical flyback generator circuit during a retrace.
The power output stage
is thermally protected by
sensing the junction temperature and shutting off the
current source of the power stage.
15
The DC bias point is maintained by the divider
R310, R311, and R312, Capacitors
C309 and C308
fmd the average output voltage. This voltage is then
fed back into the input of the buffer amplifier where
it is compared to a reference. Any difference in
these two voltages causes the DC bias point of the
power amplifier to self-adjust.
., .. +
B+
GND
, .......
aND
diagram 4.
4.4. VOLTAGE DOUBLER
In order to obtain sufficiently short flyback times, a
voltage greater than that required during scanning
must be applied to the yoke.
The flyback generator, during flyback
only, supplies
(to the power amplifier) a voltage equal to double the
supply voltage. Pin
15 of IC301 charges a capacitor
up to the supply voltage during a trace and then sets
this capacitor on top of the power supply during a
retrace, thus doubling the available voltage.
4.5. VERTICAL LINEARITY
Vertical linearity is achieved by feeding a current
ramp into the size pin 7 of the TDA1670(IC301).
By
varying the V. LIN VR the size and direction of the
correction ramp can adjusted from positive through
zero and to negative.
In the diagram
Vi and V2 are two out of phase
ramps that are subtracted to achieve a current ramp

diagramS.
which
is variable over a range shown by the bottom
three traces.
4.6. VERTICAL CENTERING
A current source
is connected to the cold side of
the vertical yoke. Transistor 0301 can pull DC
current from the yoke causing the picture to move up
the page. Potentiometer VR30S should be set to
center the
DATA vertically, not the raster, on the
screen.
5. SYNC PROCESSING
To help understand the complex sync processing
please refer to both the schematic and the timing
diagrams throughout this document.
5.1. COMPOSITE SYNC
Composite sync comes either from the TTL sync
input or from composite video through the sync
striper 0116. A CMOS 'XOR' exclusive-or gate
automatically restores sync polarity if necessary.
See the section on 'POLARITY RESTORATION'.
16
5.2. VERTICAL
Vertical sync
is detected by a low pass ftlter and an
'XOR' gate. Vertical sync comes from either the
verticallblanking input or the composite sync input.
5.3. HORIZONTAL
Horizontal sync
processing. See undergoes several stages of the sections on POLARITY
RESTORATION,
CENTERING. XORINTSC, and DATA
5.4. BACK PORCH
Back porch clamping pulses are created by
detecting the trailing edge of sync. The width of this
pulse should be a little shorter than the back porch.
Half of the 74LS221 sets the pulse width of the back
porch.
5.5. POLARITY RESTORATION
The polarity restoration circuit, an XOR gate, will
restore sync polarity if it was fed inverted into the
TTL sync input. The RC time constant in the
low
pass ftlter is about .1 second.
If the input is low with short positive pulses a low
pass filter inputs a low to the XOR input B. The
output of the
XOR gate will be the same as the
input. Likewise
if the input is high with short low
going pulses the low pass ftlter will input a high to
the B input of the
XOR gate causing it to invert the
sync. This way the syncs coming out of the polarity
restoration circuit
will always have short positive
pulses except during vertical.
5.6. HORIZONTAL DURING VERTICAL
XOR/NTSC
The H. sync is fed into another exclusive-or gate
that looks the same as the first but the time constant
is about 200 nano seconds. For normal
the capacitor should be jumpered out.
allow sync to flow through unchanged.
operations
This
will

In some computers to get vertical sync they simply
invert horizontal sync. This very nonstandard process
will cause tearing at the top of the page. The phase
lock loop in the horizontal section will sense that the
sync edge had moved over and will try to compensate.
Normally composite sync looks inverted but actually
the horizontal pulse is moved forward so the raising
edges are in place. With C188 in place the output
of the exclusive or gate will have an 200 nano second
pulse on both edges of the horizontal sync pulse.
Sync in
:&
X-OR
[,vv
input out
I o0 0
o 1 1
I 1 0 1
1 1 0
If'
ASl n rt.
Sync in
B
c.ll
n
rt.
Sync out
AU U Lr
Sync in
B
c.ll n
IL
Sync out
I
diagram6
The 74LS22l(IC106) looks at the raIsmg edge of
sync. Normally the raising edge is the first edge but
during vertical sync it is the second edge. In the
case of "inverted H sync" for vertical sync the
74LS22l(ICl06) must look at the first edge all of the
time whether the edge is raising or falling. To do
this the XOR gate produces a 200 nano second pulse
on both edges. The 74LS22l(IC106) will trigger on
the first pulse and ignore the second.
5.7. DATA CENTERING
The half of the 74LS22l(ICl06) on the video board
is used for data centering. The one shot triggers with
the leading edge of sync and time out with the back
17
edge of the flyback pulse. The data centering
potentiometer should be set to center the picture
within the raster.
6. VIDEO
6.1. PREAMP
The LM 120 1 is a wide band video amplifier
intended for use in high resolution monitors. The
LM120l contains a 100 MHz amplifier, driver, a black
level clamp, a background level control and an a to
40 dB attenuator circuit for contrast.
A video preamplifier is AC coupled and biased
through a resistor from a 2.4 volt reference. The
preamplifier drives an attenuator whose gain is
controlled by pin 4 (IC1Ol, ICl02, ICI03). The bias
level is maintained by comparing the output of the
attenuator with the voltage on pin 2 ( ICIOl, ICl02,
IC103). In the center of the LM120l is a one
transistor amplifier where the gain of each channel is
matched to set white level. Another amplifier
buffered by an emitter follower, brings the video out
on pin 8 (IC10l, IC102, IC103).
6.2. CLAMP
The clamp input pin 9 (IC10l, IC102, IC103)
watches the power amplifier's output during the back
porch. Any difference in pin 9 and pin 6 (IClOl,
IC102, IC103) during clamping will be amplified and
used to drive a current source which modifies the
voltage on pin 2 (IC10l, IC102, IC103). This clamp
voltage will be used to set bias level.
6.3. POWER VIDEO AMPLIFIER
This two transistor cascode amplifier has both
emitter and collector peaking to get the best
frequency response. The resistor on the base
reduces the chance of oscillation and also helps to
protect the amplifier from tube arcs. The amplifier
is buffered by an PNP/NPN emitter follower. The
output of the amplifier is isolated from tube arcing
by a carbon composition resistor and an arc arrestor.

6.4. REGULATORS
Four voltages are used to run the video amplifier
and sync processing circuit. The
150 volts is used by
the back ground to set black level. The 65 volts
is
used by the video power output amplifier. The 25
volts is reduced to 12 volts by the 7812 regulator for
use by the
LM12010 The 8 volts lights the filament
through a resistor and powers all of the digital logic
through a 7805 regulator.
7. TUBE BIASING
7.1. PROTECTION
All elements of the tube have arc protection. The
arc current should be returned through the arc
ground, not the signal ground, back to the tube in a
short direct low impedance path.
7.2. BYPASSING
Grid bypassing is referenced back to the 65 volt
supply. Then the
65 volts is bypassed to ground.
This wires all biasing grids in common mode for
maximum ripple rejection of the high current
65 volt
supply.
7.3. HEATER
The heater is powered from 8 volts dropped by a
power resistor.
18

DISASSEMBLY INSTRUCTIONS
As you see the disassembly diagram, you can disassemble the PCB from
the chassis
as the following procedures.
1. Disassemble cabinet
(1) Remove the 4 screws ( CD )retaining the rear cabinet ( cover rear ).
(2) Remove
the 4 screws ( ®)retaining the front cabinet ( cover front ).
2. Disassemble chassis
(1) Remove
the 10 screws ( ®)retaining the chassis top ( shield top ).
(2) Remove the 2 screws ( 8) )retaining the chassis rear ( chassis rear).
(3) Remove the 5 screws ( @ )retaining the chassis side ( chassis assy ).
(4) Remove
the 6 screws ( ® )retaining the chassis side ( chassis assy ).
3. Disassemble PCB
(1) Remove the 2 screws ( (j) )retaining the main PCB.
(2) Remove the 2 screws ( ®)retaining the power PCB.
(3) Remove the 6 screws ( CD )retaining the video PCB.
4. Remove the 2 screws ( ® )retaining the chassis PCB ( shield PCB).
The shield PCB will be separated from the chassis bottom ( chassis assy ).
19
4
PCB
POWER PCB
MAIN PCB
20