Tandy CM-8 User manual

TANDY®
\ .
erv1ce
Color Monitor CM-8
for Color Computer 3
Catalog Number : 26-3215
CUSTOM MANUFACTURED FOR RADIO SHACK, A DIVISION OF TANDY CORPORATION

CONTENTS
Page
SPECIFICATIONS .. ........ ..... .... .. ...... .... .. ......... .......... .. .. ...... ...... . .. .. .... ... .. ........... .. .... .. ..... ... 3
I POR TANT SERVICE SAFETY PRECAUTIONS ............... . ...... .... . .. .... .... ..... ..... .. ............ .... .. 4
TH EORY OF OPERATION
1. RGB Drive Circuit ... ...... ... .... ....... ....... ..... ..... .. ...... ................ ... ..... . .......... . ........ .. . ...... . 6
2.
Vi deo (RGB) Output .. .. ..... ,. ... ........ .............. .... . .... ... .. ......... .. ......... .... .. ... ..... ..... ...... .... 6
3. Vertical
Deflection Circuit ....... .. ....... .................... ....... ... .... ....... .. ......................... ..... . 7
4.
Horizontal Oscillator, AFC and Drive Circuit ... ..... ... ...... .... .... .. ..... .... .... .. ........ ...... ........ . 7
5.
Horizontal Output and HV Rectifier ...................... .. . ..... ......... ..... ... ..... ........ ........... .... .. 7
6.
High-Voltage Shutdown System .. .. ..... .......... .. .... . .. . .......... .. ...... ......... ......... ...... .... .. .... 9
7. Power Supply ...... .. .... ..... ...... ..... ..... .... ..... .. ..... .. . .. .. ....... .. ..... . .... . ..... .. .... ... ................. 9
8.
Audio Output Circuit .. .... . .... ..... ...... .......... .. .. .. .. ....... ........ .. .... .. ... ..... ...... .... ............ .... 12
DISASSEMBLY INSTRUCTIONS ..... ... ........ ... ......... .. .. ......... ...... ......... .. .......... ............ ..... .. .. 13
BLOCK DIAGRAM ..... ....... ..... ..... ........ ..... ...... ....... ... .... .. ......... .. .... . .... .. .. ....... .... . ...... .... ...... 14
AL IGNMENT INSTRUCTIONS
1. B + Power Circuit Adjustment .......... ................................... ...... ... .. .... .. .. ...... .. .. ...... .... 16
2. Horizontal Hold Adjustment .............. . .. ..... ............ ....... .. .. .. .... ..... .. .. .. .... .. .... .. . .. ........... 16
3. Vertical Size Adjustment .... .... .... . .. ............................ ....... ........ ..... ....... ..... ..... ..... .... ... 16
4. Focusing .... .. ....... .... ........................................... ....... .. .. .. ....... ......... ......... .. . .. ........ ... 16
5. High
Voltage Check ... . ........ ....... .. ...... ...... ...... ........ .. ...... ..... .. .............. ... ................... 17
6. V ertical-Linearity Adjustment ....... .. ..... . .. .... ..... .......... .. .......... ..... ....... .. .... ......... .. ......... 17
7. X- ra y Protector Circuit Test ..................... ......... .. ....................... ....... ....... .... .. .... ......... 17
. Color Purity Adjustment ............................................................................................. 17
9. Black and
White Tracking ........................... .......... ..................................................... 18
0. Static (Center) Convergence ............................................................. .......................... 19
. Dy
namic Convergence .......................................... ........................................... .. ........ 20
OU BLESHOOTING GUIDE ........... ......... ... ..... ..... . ..... ................. ..... ....... .... ..... .. ...... ......... 21
I RI G DIAGRAM AND PARTS LOCATION .... .... ..... .. .................. ..... ..... ... ..... . ...... .... ........ .. 25
I TED CIRCUIT BOARDS (Top and Bottom Views)
ain PCB ...... ... .. ......... ........ ............... .... .. .... ........ ............ .... ... .. ....... ..... ............... .... .... 27
CRT Socket PCB ........................................................................................................... 28
L ED PCB .............. ....... .. .... .. ......... . ........ ...... .. .......... ...... .... .. .... ..... .... ....... ............ .. ....... 28
CA BINET EXPLODED VIEW/PARTS LIST
1. Cabinet Exploded View ........... .......... .... .......................................... .. ...... .... .. ... .. ........ 31
2. Cab inet Parts List ......... ...... ..... ..... ...... ................... .... ..... ... .. .. ........... ... .... ......... .. .. .. ... 33
3. Electrical Parts List ........ ...... ... .... ... ....... .. .... ........... .. ...... . .......... . .. .... ...... ..... .. ......... .... 35
SCHEMATIC DI AGRAM ...... ... .. ....... ... ..... ....... .......... .. ....... ..... ...... ..... . ................. ... ...... .... . 47
AV EFORMS .. .. .. .. ......... ..... .......... .... ....... ..... ..... ... .. .. .... .. ....... ... .. ..... ... ..... ..... ........ ..... ..... 50
SE !CONDUCTOR LEAD IDENTIFICATION .... .
.. ............ ....... .... .. . .......... ... .... .......... .. .......... . 50
2

SPECIFICATIONS
Description Nominal Limit
1.
Power input AC 1 20V , 60Hz
2. AC input current 0.75A
+ 10%
-30%
3. Input si gnal
a) RGB video
RGB separate analog
0.8 - 2.0Vp-p (at 75 ohm)
level, positive (default)
b) Synchronous
T.T.L. level, positive going
4.0 - 5.0Vp-p
(default)
c) Audio
1.0Vp -p
4.
Resolution
a) Horizontal
480 dots
b) Vertical (non- interlaced)
225 lines
5. Brightness 30 fl. min . (white peak)
6.
Display color
All colors
7. High voltage
23 kV / Oµ.A
27.5 kV max ./ Oµ.A
8. Picture linearity
a) Horizontal 10% max .
b)
Vertical
10 % max .
9.
Synchronous (pull-in range)
a) Horizontal
15. 701 kHz
+300 H
-400 z
b)
Vertical
59 .7 Hz
-7 Hz
10.
Screen pitch 0.52 mm
Note: Nominal specs represent the design specs; all units should be able to approximate these - some will
exceed and some may drop slightly below these specs. Limit specs represent the absolute worst condit i on that
still might be considered acceptable ; in no case should a unit perform to less than within any limit spec .
3

IMPORTANT SERVICE SAFETY PRECAUTIONS
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 haz-
ards
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 10k ohm 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 outlet.)
1. The picture tube in this display monitor employs in-
tegral implosion protection.
2. Replace with a tube of the same type number for
continued safety.
3.
Do not lift the picture tube by the neck .
4. Handle the picture tube only when wearing shatter-
proof goggles and after discharging the high volt-
age 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 picture tube. However,
the picture tube does not emit measurable X-ray
radiation if the high voltage is as specified in the
" high-voltage check" instructions .
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 volt-
age below the maximum level specified.
2. It is essential that servicemen have available at all
times an accurate high voltage meter. The calibra-
tion of this meter should be checked periodically.
3. High voltage should always be kept at the rated
value -no higher. Operation at higher voltages
may cause a failure of the picture tube or high volt -
age circuitry and, also, under certain conditions ,
may produce radiation in excess of desirable levels.
4
4. When the high voltage regulator is operating proper-
ly there is no possibility of an X-radiation problem.
Every time a color chassis is serviced, the bright-
ness should 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 excessive 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 Hazards
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 be-
tween the chassis and other metal parts in the dis-
play monitor.
2. Inspect all protective devices such as nonmetallic
control knobs, insulating materials, cabinet backs,
adjustment and compartment covers or shield, iso-
lation resistor-capacitor networks, mechanical in-
sulators, 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 120-volt AC
outlet. (Do not use an isolation transformer for this
test .)
•
•
Using two clip leads, connect a 1.5k ohms, 10-watt
resistor paralleled by a 0.15µF capacitor in series
with all exposed metal cabinet parts and a known
earth ground, such as an electrical conduit or elec-
trical ground connected to earth ground.
Use an
SSVM or VOM with 1000 ohms-per-volt or
higher sensitivity to measure the AC voltage drop
across the resistor. (See Figure 1.)

• Connect the resistor connection to all exposed
metal parts having a return path to the chassis
(metal cabinet, screw heads, knobs and control
shafts, escutcheon, etc.) and measure the AC volt -
age drop across the resistor.
All checks must be repeated with the AC line cord
plug connection reversed. (If necessary, a non-
polarized adapter plug must be used only for the pur-
pose
of completing these checks.)
Any reading of 0.3 volt RMS (this corresponds to
0.2 milliamp. AC) or more is excessive and indi-
cates a potential shock hazard which must be cor-
rected before returning the display monitor to the
user.
SAFETY NOTICE
Many electrical and mechanical parts in display moni-
tors have special safety-related characteristics. These
characteristics often pass unnoticed and the protec-
tion afforded by them cannot necessarily be obtained
by using replacement components rated for higher
voltage, wattage, etc.
Replacement parts that have these special safety
characteristics are identified in this manual; electrical
components having such features are identified by a
6 and shaded in the Replacement Parts Lists and
Schematic Diagram. For continued protection, replace-
ment parts must be identical to those used in the origi-
nal circuit. The use of a substitute replacement part
that does not have the same safety characteristics as
specified in
this service manual, may create shock , fire,
X-radiation or other hazards.
5
SSVM AC
SCALE
TO EXPOSED
METAL PARTS
CONNECT TO
KNOWN EARTH
GROUND
Figure 1. Leakage Current Test Circuit

THEORY OF OPERATION
1. RGB Drive Circuit
IC451 is a linear IC to amplify the RGB signals.
The DC restoration system of IC451 provides control
of the simultaneous amplitude (contrast) and DC level
(brightness) of RGB .
The
synchronizing signal, as a DC restoration pulse, is
fed
from pin @ of IC601 to pins @ and @ of
IC451.
·2. Video (RGB) Output (Fig. 2)
An RGB drive system is util ized in the video output cir-
cuit of this unit. The function of this circuit is to com-
bine the color signals and the brightness signal, and
amplify them sufficiently to drive the cathodes of CRT.
145V DC must be applied to the output transistor cir-
cuit (0851, 0861, 0871). When the horizontal output
circuit is operating, a pulse used for providing 145V DC
and driving AFC circuit is developed incidentally at a
winding of the horizontal output transformer (flyback
transformer T602).
0851
RED OUTPUT
FROM
PIN@
OF IC451
R862
R-BIAS
This pulse is taken from terminal @ ofT602 and recti-
fied by
D717 , and then used as 145V DC.
--··- -
The brightness signal from the Blanking transistor
(0402) is applied to the emitters of 0851, 0861 and
0871.
C853, C854 and C855 are peaking capacitors.
Color signals from the outputs of IC451 are applied
to the bases of 0851 , 0861 and 0871 . The picture
tube used in this unit is a precision, inline gun - type.
The control gr id (G 1) and the screen grid (G2) are com-
mon with respect to the red, green and blue cathodes.
Consequently, the emitter circuits of 0851, 0861 and
0871 are provided with bias controls (R862 , R863
and R864, respectively) for picture tube cut-off ad-
justment. Drive controls (R856 and R858) are provid-
ed in
the emitter circuits of 0851 and 0871 for white
balance adjustment.
R868
R865
R856
0861
R-DRIVE
R869
FROM
PIN@)
CRT
R866
OF IC451
R863
G-BIAS
C851
0871
BLUE OUTPUT
R870
FROM
PIN@
R867
OF IC451
R861
R864 C852
B-BIAS
---
+145V
FROM
R858
B-DRIVE
VIDEO DRIVE
CIRCUIT
Figure 2. Video Output Circuit
6

3. Vertical Deflection Circuit
The vertical sync. signal with positive polarity is ap-
plied
to pin 0of the vertical and horizontal IC (IC601 ).
Pin @ of IC601 is connected to the internal vertical
oscillator circuit. The frequency of the oscillator can
be
controlled by the voltage of pin @ which can be
varied
by V.HOLD VR (R514). The sawtooth signal is
obtained by the integrating circuit which is connected
between pin @ and pin @. . . . .
The oscillator output is fed to the vertical drive c1rcu1t
through a buffer circuit. Its output, derived from pin
0 ,is applied to the vertical output circuit (IC 501 ).
The sawtooth wave is applied to pin@ of IC601 as
an
AC feedba ck signal.
The output circuit of IC 501 is controlled by V-SIZE VR
(R 507) to vary the vertical size of the raster .
The verti cal linearity control (R 526) is part of an in-
tegrating circuit which controls the line arity of the
sawtooth waveform .
4. Horizontal Oscillator, AFC and Drive Circuit
The horizontal sync. signal with positive polarity is ap-
plied
to pin @ of IC601 .
The output from the flyback transformer (T602) is in-
tegrated and connected to pin @ of IC601 as part
of the automatic frequency control circuit.
H. CENT control (R623) determines the relative posi -
tion of the raster and picture.
The horizontal oscillation frequ ency can be. controlled
by H. HOLD VR (R607) connected to pin @ of IC601.
The horizontal frequency is obtained from pin @ of
IC601 , and is fed to the next horizontal drive circuit.
From Pin.@
of IC601
C609 l
0601
HOR IZ . DR IVE
The pulse - switching mode of the driver and output
stage is a reverse polarity type; that is, when the driver
transistor 0601 is ON, the output transistor 0602 is
OFF.
5. Horizontal Output and HV Rectifier
(Figs.
3-5)
The horizontal dirve signal, developed at pin @ of the
deflection processor integrated circuit (IC601 ), is am-
plified through the horizontal drive stage (0601) and
coupled to the base of the horizontal output circuit via
the horizontal drive transformer (T601 ). Refer to Fig. 3.
The horizontal output circuit generates the horizontal
scanning signal and a high voltage to be applied to the
picture tube . The function of the horizontal output
stage (0602) is to serve as a switch for the horizontal
output circuit. Refer to Fig. 4.
During the horizontal scanning period, 0 operates (S 1
is
closed, S2 is open) and the current is applied in one
direction through the horizontal coils of the deflection
yoke (LY) and the capacitor (C). During retrace time ,
O is inoperati ve (S 1 is open, S2 is closed) and the cur -
rent is applied in the opposite direction through the
damper diode (D), the horizontal coils of the deflection
yoke (LY) and the capacitor (C).
The high voltage applied to the anode of the picture
tube is generated by boosting the pulse from the col-
lector of 0602 through T60 2 during the flyback (re -
trace) period and applying this boosted pulse to a series
of silicon rectifiers . Refer to Figure 5.
High voltage regulation is accomplished internally in
T602.
C611
R614
T60 1
HORIZ . DRIVE
R613
To BASE
of 0602
Figure 3. Horizontal Drive Circuit
7

To D.Y.
115V
O(S1)
DAMPER I
DIODE (S2) C
':' .,.
(A)
LY
(DEFLECTION
COIL)
vcc
LY
r r
r@=-- 2
c::) s1J
52
1: c - :
I L@I-- __)1
"'----------"4---·1·---
(B)
Figure 4. Equivalent Circuit of Horizontal Output Circuit
C625 -C628
R714
r---
1
i------TO CRT
SE . COND ANODE
)------- TO CRT FOCUS
1----- TO CRT SCREEN
To Blanking ~ --- ~
'------To H orizontal
AFC DET . C ir cuit
1----'Vlt1---- To CRT Heater
l----JV.,..,_---1t-.....-__,~18V
C715
I_ --- --- --
C510
Figure 5. Horizontal Output and HV Rectifier Circuit
8

6. High Voltage Shutdown System
The shutdown circuit prevents the high voltage from
rising above a preset level.
Under normal operating conditions, this circuit is in-
active.
Operation of the protector circuit depends upon a heat -
er
pulse which appears at pin@ of the horizontal out -
put transformer (T602) . It monitors a heater pulse
rectified by 0603 . If the incoming high voltage increa-
R615
0603 0605
ses and exceeds its limit , the heater pulse voltage also
increases. As a result, there is a larger voltage
produced to charge C617 so that its potential will
eventually be higher than the knee voltage (+ 22V) of
the Zener diode (0605) turning it ON. With D605
turned ON, the X-r ay protector (of IC601) operates to
stop the horizontal oscillator circuit, shutting down the
resultant high voltage.
R618
FROM PIN@
OF T602
~~-91~--41>----41>-----4--~-l\.IV'-~---~----'VVI
IC601
(
HEATER )
PULSE
R619
+ +
C617 C607
Figure 6. High Voltage Shutdown System Cirucit
7. Power Supply (Figs. 7-9)
The power supply circuit is a blocking oscillator type
switching power circuit and substantially consists of
the rectifier / smoother , blocking oscillator, control, and
output rectifier / smooth er circui t s.
The AC input voltage is full-wav e rectified by the rec -
tifier / smoother circuit and then placed on the smooth-
ing capacitor as a DC voltage.
The DC voltage is appli ed to the bloc ki ng oscillator
circuit .
The blocking oscillator circuit operates at an oscilla -
ti on frequency and duty ratio that depends upon the
action of the control circuit.
St abilization of the ou tput voltage is accomplished by
changing the conducting period of the ou tput tr ansis-
tor used in the blocking oscillato r circuit.
Operational Description
When the power is turned on , a small current flows
to the base of the output trans i stor (0 702 ) via the
startup resistor ( R712 ). As a result , the collecto r cur-
rent flows through the pr i mary windings@ and Q)
of the converter transformer , whi ch produ ces an elec-
tromotive force between those windings i rrespective
of the magnitude of the collector current, resulting in
a
voltage being indu ced between the driving w indings
@ and @. The induced voltage is positively feed-
back to the base of the output transistor (0 702 ) to in-
crease the base current of this transistor , resulting in
a
further increase in the collector current. The above
operation occurs instantaneously to impress sufficient
base current on 0 702 , keeping it on. The collector cur -
rent of 0 702 , determ i ned by the equation i = V/L ·t ,
increases rectilinearly with time.
9
While the control circuit is at rest , the collector cur -
rent increases with time , and the moment it reaches
h FE times that of the base current, 0 702 turns off.
. The control circuit always applies to the error amplifi -
er circuit a voltage induced in the detecting winding
situated at the primary side of the converter trans -
former .
This charges the capacitor (C7 14 ) while 0702 is off .
Also the capacito r (C708) is cha rged with a reverse vol-
ta ge produced between the driving windings @ and
@ while 0 702 is off . This voltage is a positive con-
stant voltage .
If the voltage induced in the detecting winding be-
comes greater than a specified value, it also exceeds
the voltage of th e Zener diode in the error amplifier,
resulting in a voltage being applied to the emitter of
0701 . This causes the base current of 0701 to flow ,
turning it on .
The flow of the collector curren t of 0701 produces a
voltage in the resistor connected between the collec -
tor of 0701 and the ground . When this voltage reaches
the gate trigger voltage , the thyristor whose gate is
connected to the above resistor turns on .
Th e instant the thyristor turns on , a current flows
through R710 , the thyristor , the emitter and base of
0 702 ; in this sequence , the charging voltage of C 708
is used as a power source , causing the base current .
of 0 702 to stop and thus 0 702 to turn off.
When Q 702 turns off, the energy accumulated be-
tween the primary windings@ and G) while 0702
is on is transmitted to the secondary winding and then
fed to the load via the rectifier circuit (D 71 0, C 711).

AC120V
60Hz
F701
F701
AC120V
60Hz
L702
LINE
FILTER
0710
R714
POWER
R631
CONVERTER
SW701
0701 ,...:, 0704
HORIZ.
BRIDGE
REGULATOR
OUTPUT
RECTIFIER
CIRCUIT
XFMR .
R716
Figure 7. Block Diagram of Power Supply
PR701 .
L701
ADG
~ f
m
z
--i
Figure 8 . ADG Circuit
10
+115V
0717
+145V
+18 V
+12V
R401
+5 . 1V
R481
TIME ---

8. Audio Output Circuit (Fig. 10)
The audio output circuit is an output transformerless
system which employs a bipolar analog IC. The audio
signal
coming out of the computer is applied via C301
and the buffer amplifier 0301 to pin (D of IC301. The
signal fed into IC301
is delivered to pin ® through PRE -
DR IVER, DRIVER, and POWER-OUT.
The audio signal coming out of IC301 is sent via C303
to the speaker.
Characteristi cs in low -freque ncy band are determined
by C305 and C303; c haracteristi cs in high - frequency
band are determined by C308 .
The amplifi c ation factor of IC301 is determined by
R
30 7.
Power is supplied to IC301 through pin @.
+
When current does not flow through pin @, the volt -
age at pin@ is increased. Due to the increase in volt -
age, a current flows into 0302 through R310 and
D304 : 0302 is then turned on so that current flows
through R308 and the voltage at pin @ is decreased.
When current flows through pin @ of IC301, the volt -
age applied
to pin @ is decreased . If the voltage is
decreased,
the cu r rent through R310 and D304 is off
and 0302 is turned off , so that the current through
R308 is cut off , and the voltage at pin @is increased.
Thus the volt age at pin @ of IC301 is stabilized.
R3 15
R3 14 C3 09
C3 1I 0 3 0 1
SOUN D VOi.
R310
03 02
Figure 10 . Audio Output Circuit
12
03 0 2
R3 1I
R3 01
+C3 0 6
TO PIN ® +1 a v
OF FBT
TO SP
( 8 ohm )

DISASSEMBLY INSTRUCTIONS
1. Remove the six screws Q) retaining the rear
cabinet.
Remove the re ar cabinet. (Figure 11A)
Note: The CRT must be discharged . Remove the
speaker leads from the PCB-A. Refer to the high
voltage discharge procedure on page 4.
.2. (1) Remove th e CRT's second anode cap@ from
the CRT.
(2) Unso lder the grounding strap and remove the
PCB -B (CRT PCB) le ad of the CRT.
(3) Remove the PCB-B.
(4) Loosen the wire holder on the PCB-A and dis-
connect the connector K. (Figure 11B)
'\
Ma in PC 8
( PCB- A l
13
(5) Disconnect the conn ect ors NA and M on the
PCB-A (main PCB).
(6) Loosen the wire holder fi xing the RGB output
lead, degaussing lead, speaker lead and LED
lead. (Figure 118)
(7) Remove
the PCB-A ( main PCB) from the fron t
cabinet .
3. Remove
screw @in the PCB -C (LE D PC B) and
remove PCB-C
from the front cabinet. (Figure 11 8)
Note: When servicing, be suff ici ently careful with the
control door since it may detach from the
cabinet if it touches the su rfac e wh il e the set
is i nc lined toward the fr o nt .
Figu re 11A. Removal of Cabinet
Figure
11B. Removal of PC Bs

ALIGNMENT INSTRUCTIONS
Note:
For this adjustment, connect the Monitor to the Color
Computer 3 (Cat. No. 26 - 3334). A lthough the Monitor
is adjusted before it is delivered, readjustment may be
required when the setting position is changed or when
a component is replaced.
Test Pattern Program Examples:
White pattern and 'H' character pattern.
10 WIDTH 80 : PALETTE RGB
20 PRINT" This program will produce a white screen when run."
30 PRINT" To generate th e 'H' character pattern, press any key , after the screen is white ."
40 PRINT"Press <ENTER > to begin ."
50 A$ = INKEY$: 1F A$ = " " THEN 50
60 POKE&HFF98,4
70 POKE&HFF99 ,& H75
80 PALETTE 0,0
90 CLS 1:PALETTE 0, 64
100 A$ = INKEY$: 1F A$ = " " THEN 100
110 FOR A = 1TO1919
120 PRINT"H ";: NEXT
130 GOTO 130
140 END
Crosshatch pattern :
10 REM * * * * Crosshatch pattern - SH x 12V * * * *
20 WIDTH SO: PALETTE RGB:PALETTE O,O:PALETTE 8, 54:CLS9
30 HSCREEN 2
40 FOR Y = 0 TO 192 STEP 16
45 H COLOR 4
50
HLINE (0,Y) - (320,Y) ,PSET
60
NEXT
70 FOR X = 0 TO 320 STEP 40
80
HLINE(X,0) -(X, 192 ),PSET
90 NEXT
100 GOTO 100
110 END
Green pattern:
10 REM **** Green pattern ****
20 WIDTH 80:PALETTE RGB
30 CLS1
40 GOTO 40
50 END
15

Gray scale (color bars) pattern:
10 REM * * * * Gray scale (color bars) pattern
20 WIDTH 80:PALETTE RGB
****
30 PR INT"This program will generate 16 colored bars per screen."
40 PRINT"To view the next set of 16 colors, press any key."
50 PRINT" Press <ENTER> to begin."
60 A$ =1NKEY$:1F A$="" THEN 60
70 ON BRK GOTO 250
80 HSCREEN 2
90 GOSUB210
1 00 FOR R= 0 TO 15
110 HCOLOR R, 15
120 HLINE(R * 20,0)-((R + 1)*20, 192),PSET,BF
130 HCOLOR 0,0
140NEXTR
150 FOR N = 0 TO 3
160 GOSUB 210
170 A$= INKEY$: 1F A$=" " THEN 170
180 NEXT N
190 PALETTE RGB
200 END
210 FOR R= 0 TO 15
220 PALETTE R,(N*16)+R
230 NEXT R
240 RETURN
250 PALETTE RGB:END
1. B+ Power Circuit Adjustment
(Instrument in use: a 20 Kohm/V tester)
(1) Be sure that the AC line voltage is above 114V.
(2) Rotate the B + voltage adjusting control (R703) to
provide a DC voltage of 115V between the TP701
and TP702.
Note 1: If the AC line voltage is below 114V, the
DC voltage may not increase to 11 5V, but
this is not a problem related to this ad-
justment.
Note 2: Clockwise rotation of the B + voltage ad-
justing control will increase the B + pow-
er supply voltage .
2. Horizontal Hold Adjustment
(1) Operate the computer in such a way that the let-
ter "H" covers the entire screen (data display peri-
od : 44 . 698 µ,S horizontal, 14.331 mS vertical) .
(2)
Adjust the horizontal hold control (R607) until the
picture on the screen becomes still (synchronized).
(3)
Turn the power switch on and off several times to
check that the picture does not fluctuate.
16
3. Vertical Size Adjustment
(1) Operate the computer in such a way that the let -
ter "H" covers the entire screen (data display peri-
od:
44.698 µ,S horizontal , 14.331 mS vertical) .
(2)
Adjust the vertical size control (R 507 ) so that the
height of the displayed pattern is 7.48 inches ( 190
mm).
4. Focusing
(1) Operate the computer to display the alphabetical
characters on the screen.
(2)
Set the brightness control at the center position.
(3) Rotate the focus control (part of T602) for the best
focus.
(4) Change the position of the brightness control to
confirm that the picture remains focused.

5. High Voltage Check
High voltage is not adjustable but must be checked to
verify that the Monitor is operating within safe and ef-
ficient design limitations as specified .
1.
Operate the Monitor for at least 15 minutes at
1 20VAC line voltage with the computer display-
ing a white pattern.
2. Turn off switch SW851 on PCB-B.
3. Rotate the screen control (on T602) to the maxi-
mum (counterclockwise) end of its rotation .
4. Connect an accurate, high-voltage meter to the
CRT anode. Check that the reading is approximate -
ly 22 . 0kV to 23 . 0kV (at 0 beam current) .
If a correct reading cannot be obtained, check the cir-
cuitry for malfunctioning components. On comp letion
of the voltage check, readjust the screen control for
proper operation as detailed in the "Black and White
Tracking " procedures.
6. Vertical-Linearity Adjustment
1. Operate the computer in such a way that the let-
ter "H" covers the entire screen (data display peri-
od:
44.698 µS hori zonta l, 14.331 mS vertical) .
2. Adjust the V-Lin . control (R526) until the height
of a character varies no more than 10 percent from
the average character size.
7. X-ray Protector Circuit Test
After service has been performed on th e horizontal
deflection system , the high voltage system and the X-
ray
protector circuit must be tested for proper opera-
tion as follows:
1. Apply 1 20V AC, using a variac transformer .
2.
Operate the computer in such a way that the en-
tire screen displays a white signal, (data display
period: 44 . 698 µS horizontal, 14 .331 mS vertical).
3.
Check the voltage of test point TP601. (Its voltage
should be about 18.5V DC .)
4. Connect the cathode of the D 504 and TP601
through a short clip lead. Then, connect another
short clip lead between both sides of R 522 . The
operation of the horizontal oscillator is stopped by
connecting these points.
5. To start the operation again, remove the two short
clip leads and connect TP602 and chassis ground
(TP702) using a short clip lead. Disconne ct the
short clip lead as soon as the Monitor operates
again with a normal picture.
6. If the operation of the horizontal oscillator does not
stop in step 4, the circui t must be repaired before
the set is returned to the customer .
17
8. Color Purity Adjustment
The Monitor must have been operat ing 15 minutes pri-
or
to this procedure, and with the faceplate of the CRT
at room temperature. The Monitor is equipped with an
automatic degaussing circuit. However, if the CRT
shadow mask has become exces siv ely magnetized, it
may be necessary to degauss it with a manual coil. (Do
not switch the coil off while the raster shows any ef-
fect from the coil.)
1. Check for the correct location of all neck compo-
nents. Refer to Figure 13.
2. Rough in the static convergence at the cen ter of
the CRT, as explained in the static convergence
procedure .
3.
Rotate the contrast control to the center of its
range and rotate the brightness control to its max -
imum clockwise position.
4. To obtain a blank raster, disconnect E (Signal in-
put) from PCB-A .
Rotate the screen control (part of T602) clockwise
until a normal raster is obtained.
5. Rotate the red bias (R862) and blue bias (R864)
controls to the maximum counterclockwise po-
sitions.
Rotate the green bias control (R863) sufficiently
in a clockwise direction to produce a green raster.
6. Loosen
the deflection yoke clamp screw and pull
the deflection yoke as close as possible to the pu-
rity and convergence magnets assembly .
7. Begin the following adjustment with the tabs on
the round purity magnet rings set together. Initial-
ly,
move the tabs on the round purity magnet rings
to
the side of the CRT neck. Then, slowly separate
the two tabs while at the same time rotating them
to ad just for a uniform green verti c- al band at the
center of the CRT screen. Refer to Figure 12 .
8.
Carefully slide the deflection yoke forward to
achieve green purity (uniform green screen).
Tighten the deflect ion yoke clamp scr ew.
Note: Center purity is obtained by adjusting the
tabs on the round purity magnet rings. Outer edge
purity is ob tained by sliding the deflection yoke
forward .
9.
Check for red and blue-field purity by reducing the
output of the green bias control (R863) and alter-
nately increasing the output of the red (R862) and
blue (R864) bias controls , and touch up the ad-
justment, if required.
10. Reconne ct E to PCB-A .
11 . Perform the "Black and White T rac king "
procedures .

CRT
GREEN RASTER
Figure 12. Color Purity Adjustment
PURITY MAGNETS
FOUR-POLE CONV. MAGNETS
SIX-POLE CONV . MAGNETS
A
36mm
(1 .417 inches)
A
DEFLECTION YOKE Tl LT
ADJUSTMENT WEDGE
Figure 13. Picture Tube Neck Components Location
9. Black and White Tracking
1. Make the following settings.
Contrast control (R465) and brightness control
(R459): maximum
R/G/B bias controls (R862, R863 , R864) : minimum
R/B drive controls (R856, R858): center
2. Set the sub - contrast control (R454) to center po -
sition .
3.
Connect an oscilloscope between TP451 and the
ground.
Adjust the sub - brightness control (R458) to
achieve a pedestal level of 4.8 V De.
4.8Voc
(White Signal)
_____________ _J_ ___ 0 Level
4. Hook up the computer and give an input for a black
signal.
(The raster should not be shining during the whole
display period : horizontal, 44 . 698 µ.sec and verti -
cal,
14 . 331 msec .)
18
5. Turn off th e sw it ch ( SW851 ).
6. Adjust the scre en control (on T602) so that the
raster is dimly shining.
7. Achieve white balance using the other two bias
controls for the shining color (for example , blue and
green when the raster is shining in red).
8.
Adjust the screen control to obtain the "just cut
off" position .
9.
Using the computer, feed a white signal input in-
stead of the black one.
10 . Turn on the service switch (SW851) .
11. Achieve white balance again with the R/B drive
controls (R856 , R858).
12. Using a gray scale signal (16-graduation color
difference signal is formed during all the display
period : horizontal 44.698 µ. sec and vertical
14. 331 msec) , check to see if the 16 colors show
up and if the low and high white balance is proper.
If any of the 16 colors fails to show up , fine - adjust
the sub-brightness control (R458) . If the low and
high white balance is not achieved , readjust the
R/B drive controls .
13. Set the sub - contrast co ntrol ( R454) to obtain a
beam level of 5.2 ~gf V.
14 . Repeat Step 12 abo v e.

10. Static (Center) Convergence
(Figs.
13-16)
1. Switch the display monitor ON and allow it to
warm up for 15 minutes.
2. Operate the computer in such a way that the en-
tire screen is a crosshatch pattern (display period :
44 . 698 µS horizontal , 14 . 331 mS vertical) on the
center of the CRT screen. (Fig. 14)
Proceed as follows :
a. Locate the pair of four-pole magnet rings . Ro-
tate the individual rings (change spacing be-
tween tabs) to converge the vertical red and
blue lines. Rotate the pair of rings (maintaining
spacing between tabs) to converge the horizon -
tal red and blue lines. Re fer to Figure 15.
b. After completing th e red and blue center conver-
gence, locate the pair of six-pole magnet rings .
Rot ate the individual rings (change spacing be-
tween tabs) to converge the vertical red and
blue (magenta) and green lines. Rotate the pair
of rings (maintaining spacing between tabs) to
conve rge the horizontal red and blue (magenta)
and green lines. Ref er to Figur e 16 .
19
Figure 14. Crosshatch Pattern
t
RED
Figure 15. Static Convergence A
I
BLUE / ~ ~
RED
1
~
-- t---- ·
t
GREEN
Figure 16 . Static Convergence B
Hor i zontal :
9
Lines Min .
Vertical :
13 Lines Min.

11. Dynamic Convergence (Figs. 17 -19)
Dynamic convergence (convergence of the three color
fields at the edges of the CRT screen) is accomplished
by proper insertion and positioning of three rubber
wedges between the edge of the deflection yoke and
the funnel of the CRT .
This is accomplished in the following manner:
1. Switch the display monitor ON and allow it to warm
up for 15 minutes.
2. Apply the crosshatch pattern (Fig. 14) from the
computer to the display monitor. Observe spacing
between lines around the edges of the CRT .
3. Tilt the deflection yoke up and down . Insert tilt ad-
justment wedges G) and 0 between the deflec -
tion yoke and the CRT until the misconvergence
illustrated in Figure 17 has been corrected .
4. Tilt the deflection yoke right and left. Insert tilt ad-
justment wedge Q) between the deflection yoke
and the CRT until the misconvergence illustrated
in Figure 18 has been corrected .
5. Alternately change the spacing between , and depth
of insertion of , the three wedges until proper dy -
namic convergence is obtained .
6. Check pur i ty and readjust, if necessary.
20
'
GREEN
~ /..._RED
BLUE.-.! /-- (BLUE)
(RED) / BLUE(RED).
1---------
I' -rGREE~
I \ RED (BLUE)
..,.1.;
---
\
Figure 17. Dynamic Convergence A
'
I
.. .
I
I
I
BLUE
(RED)
i---------s
I t RED
: (BLUE) :
1 +i .. I
I
I RED I
~(BLUE)~ I
l _i. __________ I
BLUE
(RED)
'
!.
I
I
'
I
Figure 18. Dynamic Convergence B
DEFLECTIOI\
YOKE
Figure 19. Deflection Yoke Rear View