Hitachi CM625ET Schematic

No. 0503

CM625ET

SERVICE MANUAL

CAUTION:

Before servicing this chassis, it is important that the service technician
read the “Safety Precautions” and “Product Safety Notices” in this
service manual.

ATTENTION:

Avant d’effectuer l’entretien du châassis, le technicien doit lire les
«Précautions de sécurité» et les «Notices de sécurité du produit»
présentés dans le présent manuel.

VORSICHT:

Vor Öffnen des Gehäuses hat der Service-Ingenieur die
„Sicherheitshinweise“ und „Hinweise zur Pro duktsicherheit“ in diesem
Wartungshandbuch zu lesen.

MANUEL D’ENTRETIEN
WARTUNGSHANDBUCH

Data contained within this
Service manual is subject to
alteration for improvement.

Les données fournies dans le
présent manuel d’entretien
peuvent faire l’objet de
modifications en vue de
perfectionner le produit.

Die in diesem
Wartungshandbuch
enthaltenen Spezifikationen
können sich zwecks
Verbesserungen ändern.

October 2000

ENGLISH

SAFETY PRECAUTIONS

WARNING: The following precautions must be observed.

ALL PRODUCTS

Before any service is performed on the chassis an
isolation transformer should be inserted between the
power line and the product.

1. When replacing the chassis in the cabinet, ensure
all the protective devices are put back in place.

2. When service is required, observe the original
lead dressing. Extra precaution should be taken to
ensure correct lead dressing in any high voltage
circuitry area.

3. Many electrical and mechanical parts in
HITACHI products have special safety related
characteristics. These characteristics are often not
evident from visual inspection, nor can the
protection afforded by them necessarily be
obtained by using replacement components rated
for higher voltage, wattage, etc. Replacement
parts which have these special safety
characteristics are identified by marking with a

! on the schematics and the replacement parts
list.
The use of a substitute replacement component
that does not have the same safety characteristics
as the HITACHI recommended replacement one,
shown in the parts list, may create electrical
shock, fire, X-radiation, or other hazards.

4. Always replace original spacers and maintain lead
lengths. Furthermore, where a short circuit has
occurred, replace those components that indicate
evidence of overheating.

5. Insulation resistance should not be less than 2M
ohms at 500V DC between the main poles and
any accessible metal parts.

6. No flashover or breakdown should occur during
the dielectric strength test, applying 3kV AC or

4.25kV DC for two seconds between the main
poles and accessible metal parts.

7. Before returning a serviced product to the
customer, the service technician must thoroughly
test the unit to be certain that it is completely safe
to operate without danger of electrical shock. The
service technician must make sure that no
protective device built into the instrument by the
manufacturer has become defective, or
inadvertently damaged during servicing.

CE MARK

1. HITACHI products may contain the CE mark on
the rating plate indicating that the product
contains parts that have been specifically
approved to provide electromagnetic
compatibility to designated levels.

2. When replacing any part in this product, please
use only the correct part itemised in the parts list
to ensure this standard is maintained, and take
care to replace lead dressing to its original state,
as this can have a bearing on the electromagnetic
radiation/immunity.

PICTURE TUBE

1. The line output stage can develop voltages in
excess of 25kV; if the E.H.T. cap is required to be
removed, discharge the anode to chassis via a
high value resistor, prior to its removal from the
picture tube.

2. High voltage should always be kept at the rated
value of the chassis and no higher. Operating at
higher voltages may cause a failure of the picture
tube or high voltage supply, and also, under
certain circumstances could produce X-radiation
levels moderately in excess of design levels. The
high voltage must not, under any circumstances,
exceed 29kV on the chassis (except for projection
Televisions).

3. The primary source of X-radiation in the product
is the picture tube. The picture tube utilised for
the above mentioned function in this chassis is
specially constructed to limit X-radiation. For
continued X-radiation protection, replace tube
with the same type as the original HITACHI
approved type

4. Keep the picture tube away from the body while
handling. Do not install, remove, or handle the
picture tube in any manner unless shatterproof
goggles are worn. People not so equipped should
be kept away while picture tubes are handled

LASERS

If the product contains a laser avoid direct exposure to
the beam when the cover is open or when interlocks are
defeated or have failed.

FRANÇAIS

CONSIGNES DE SECURITE

AVERTISSEMENT: vous devez respecter les précautions suivantes

POUR TOUS LES PRODUITS

Avant d’effectuer une intervention d’entretien sur le
châssis, vous devez insérer un transformateur d’isolement
entre la ligne d’alimentation électrique et le produit.

1. Lors de la remontage du châssis dans le coffret,
vérifiez que tous les dispositifs de protection sont
remis en place.

2. Lorsqu’une intervention d’entretien s’avère
nécessaire, respectez l’agencement d’origine des
conducteurs. Vous devez prendre des précautions
supplémentaires pour garantir un agencement correct
des conducteurs dans toutes les zones où des circuits
haute tension sont présents.

3. De nombreux composants électriques et mécaniques
des appareils HITACHI ont des caractéristiques
spéciales de sécurité. Bien souvent, ces
caractéristiques ne sont pas évidentes lors d’un
examen visuel et la protection qu’ils offrent n’est pas
forcément garantie si vous utilisez des composants de
rechange conçus, par exemple, pour une tension plus
élevée, une puissance plus forte. Les pièces de
rechange qui offrent des caractéristiques spéciales de
sécurité sont identifiées par un repérage comportant

le symbole ! sur les schémas et sur la
nomenclature des pièces de rechange.
L’emploi d’un composant de rechange qui ne
respecte pas les mêmes caractéristiques de sécurité
que la pièce de rechange que recommande HITACHI
et qui figure dans la nomenclature risque de
provoquer un choc électrique, un incendie, des rayons
X ou d’autres dangers.

4. Remettez toujours en place les entretoises d’origine
et respectez la longueur des conduites. En outre, à la
suite d’un court-circuit, remplacez les composants
présentant des signes de surchauffe.

5. La résistance d’isolement doit être supérieure ou
égale à 2 méga ohms à 500 V c.c. entre les pôles
principaux et des composants métalliques
accessibles, quels qu’ils soient.

6. Aucun claquage et aucune rupture ne doit se produire
pendant l’essai de résistance diélectrique à la suite de
l’application d’une tension de 3 kV c.a. ou de 4,35
kV c.c. pendant deux secondes entre les pôles
principaux et des composants métalliques
accessibles.

7. Avant de remettre au client un produit qui a fait
l’objet d’un entretien, le technicien qui s’est chargé
de cette intervention doit tester à fond cet ensemble
pour s’assurer qu’il ne présente aucun danger
opérationnel et aucun risque de choc électrique. Ce
technicien doit s’assurer qu’aucun des dispositifs de
protection intégrés à cet instrument par le fabricant
n’est défectueux ou n’a été endommagé de façon
accidentelle lors de l’entretien.

LABEL CE

1. Les produits HITACHI peuvent avoir reçu le label
CE qui figure sur la plaque signalétique pour indiquer
que cet ensemble contient des composants qui ont fait
l’objet d’une homologation spécifique de respect des
normes de compatibilité électromagnétique en
fonction de niveaux bien spécifiés.

2. Lors du remplacement d’un des composants de ce
produit, utilisez uniquement le composant correct
identifié dans la nomenclature afin de maintenir le
respect de cette norme ; en outre, vous devez
également ramener l’agencement des conducteurs à
son état d’origine car cela peut avoir une influence au
niveau des rayonnements électromagnétiques et sur la
protection contre ces rayons.

PICTURE TUBE

1. L’étage de sortie des lignes peut développer des
tensions de plus de 25 kV ; s’il faut retirer le chapeau
de protection contre les tensions extrêmement
élevées, il convient de décharger l’anode contre le
châssis par le biais d’une résistance de forte valeur
avant de déposer ce chapeau du tube image.

2. La haute tension doit toujours se maintenir à la valeur
nominale du châssis et ne pas dépasser cette dernière.
Un fonctionnement à des températures élevées peut
provoquer une défaillance du tube image ou l’entrée
d’une tension élevée. Dans certains cas, cela peut
même provoquer des rayons X d’un niveau
légèrement supérieur aux valeurs de calcul. Cette
haute tension ne doit en aucun cas dépasser 29 kV sur
le châssis (à l’exception des téléviseurs de
projection).

3. La principale source de rayons X de cet appareil est
le tube image. Le tube image employé pour assurer la
fonction susmentionnée dans ce châssis est
spécialement construit pour limiter des rayons X.
Pour maintenir cette protection contre les rayons X, il
faut remplacer le tube d’origine d’un type agréé par
HITACHI par un autre tube de même type.

4. Lors des manipulations, ne tenez jamais le tube
image contre le corps. Pendant toutes les opérations
d’installation, de dépose et de manipulation de ce
tube image, quelle que soit la méthode employée,
vous devez toujours porter des lunettes de sécurité
anti-éclatements. Les personnes qui ne portent pas ce
type de lunettes doivent se tenir à l’écart du tube
image lors de la manipulation de ce dernier.

RAYONS LASER

Si ce produit contient un rayon laser, évitez toute
exposition directe à ce faisceau lors de l’ouverture du
couvercle ou lors de l’élimination des verrouillages de
sécurité ou après défaillance de ces verrouillages.

DEUTSCH

SICHERHEITSVORKEHRUNGEN

WARNUNG: Die folgenden Vorkehrungen müssen eingehalten werden.

ALLE PRODUKTE

Bevor die Grundplatte gewartet wird, sollte ein Trenntrafo
zwischen die Netzleitung und das Produkt eingebracht
werden.

1. Wenn die Grundplatte in das Gehäuse zurückgestellt
wird, stellen Sie sicher, dass alle
Schutzvorrichtungen wieder an ihrem Ort sind.

2. Wenn Wartung erforderlich ist, halten Sie die
originale Verdrahtungsart ein. Besondere Vorsicht ist
nötig, um die korrekte Verdrahtungsart in jedem
Hochspannungsstromkreis zu gewährleisten.

3. Viele elektrische und mechanische Teile von
HITACHI Produkten haben besondere
sicherheitsbezogene Eigenschaften. Diese
Eigenschaften fallen oft nicht ins Auge, aber der
durch sie gewährte Schutz kann nicht unbedingt
erreicht werden, wenn man Ersatzteile benutzt, die
für höhere Spannung, Leistung usw. ausgelegt sind.
Ersatzteile, die diese besonderen
Sicherheitsmerkmale haben, sind in den

Prinzipskizzen und Ersatzteillisten an einem ! zu
erkennen.
Der Gebrauch von Ersatzteilen, die nicht dieselben
Sicherheitsmerkmale haben wie die empfohlenen
HITACHI Ersatzteile, wie sie in der Ersatzteilliste
aufgeführt sind, kann zu elektrischem Schlag, Feuer,
Röntgenstrahlung und anderen Gefahren führen.

4. Immer die originalen Abstandsstücke ersetzen und
die Leitungslängen beibehalten. Wo ein Kurzschluss
passiert ist, die Teile ersetzen, bei denen Überhitzung
nachzuweisen ist.

5. Der Isolierwert sollte bei 500 V Gleichstrom
zwischen den Hauptpolen und allen zugänglichen
Metallteilen nicht unter 2M Ohm liegen.

6. Bei der Prüfung auf Durchschlagsfestigkeit sollte
kein Überschlag oder Durchschlag vorkommen,
wenn zwei Sekunden lang 3 kV Wechselstrom oder
4,25 kV Gleichstrom zwischen den Hauptpolen und
allen zugänglichen Metallteilen angelegt wird.

7. Bevor das gewartete Produkt dem Kunden
zurückgegeben wird, muss der Wartungstechniker
das Gerät gründlich prüfen, um sicherzustellen, dass
es betriebssicher ist ohne das Risiko eines
elektrischen Schlages. Der Wartungstechniker muss
sicherstellen, dass keine vom Hersteller im Gerät
eingebaute Schutzvorkehrung schadhaft geworden ist
oder bei der Wartung unabsichtlich beschädigt
wurde.

CE KENNZEICHEN

1. HITACHI Produkte enthalten eventuell das CE
Kennzeichen auf dem Leistungsschild, welches
angibt, dass das Produkt Teile enthält, die eigens
zugelassen sind, um bis zu einem spezifizierten
Niveau elektromagnetische Störfreiheit zu bewirken.

2. Wenn Sie irgendein Teil in diesem Produkt ersetzen,
benutzen Sie bitte nur das korrekte Teil, das in der
Ersatzteilliste aufgeführt ist, um sicherzustellen, dass
dieser Standard eingehalten wird, und geben Sie acht,
die Verdrahtungsart in ihren ursprünglichen Zustand
zurück zu versetzen, weil das einen Einfluss auf die
elektromagnetische Abstrahlung/Störsicherheit haben
kann.

BILDRÖHRE

1. Die Leitungsausgangsstufe kann Spannungen von
mehr als 25 kV entwickeln; wenn die
Höchstspannungskappe entfernt werden muss,
entladen Sie die Anode zum Gehäuse über einen
hochohmigen Widerstand, bevor Sie sie aus der
Bildröhre entfernen.

2. Hochspannung sollte immer auf den festgelegten
Wert des Gehäuses beschränkt bleiben und nicht
mehr. Betrieb bei höherer Spannung kann zum
Versagen der Bildröhre oder zu hoher
Spannungszufuhr führen und kann unter Umständen
auch Röntgenstrahlung hervorbringen, die leicht über
dem Konstruktionsniveau liegt. Die Hochspannung
darf auf keinen Fall 29 kV am Gehäuse überschreiten
(außer bei Projektionsfernsehern).

3. Die Hauptquelle der Röntgenstrahlung im Produkt ist
die Bildröhre. Die Bildröhre, die für die oben
erwähnte Funktion in diesem Gehäuse benutzt wird,
ist eine Spezialkonstruktion zur Begrenzung der
Röntgenstrahlung. Um den Schutz vor der
Röntgenstrahlung zu behalten, ersetzen Sie bitte die
Röhre durch denselben Typ wie den ursprünglichen
von HITACHI zugelassenen.

8. Halten Sie die Bildröhre bei der Handhabung vom
Körper weg. Sie dürfen die Bildröhre nur dann
installieren, entfernen oder handhaben, wenn Sie eine
nicht splitternde Schutzbrille tragen. Personen ohne
derartigen Schutz sollten ferngehalten werden,
solange Bildröhren gehandhabt werden.

LASER

Wenn das Produkt einen Laser enthält, setzen Sie sich
keinesfalls direkt dem Strahl aus, wenn die Abdeckung
geöffnet ist oder wenn die Verriegelung versagt.

1. DISPLAY ALIGNMENT ...............................................................1

A. Times & Display Size..................................................................................... 1

B. Picture Position.............................................................................................. 1

C. Linearity......................................................................................................... 1

D. Geometry Distortion (All Preset Mode)...........................................................1

E. Alignment Procedure .....................................................................................2

White Balance Adjustment (9300°as major temperature) Low light

F.

G. Focus Adjustment.......................................................................................... 2

H. Convergence Adjustment...............................................................................3

I. Presetting Modes Adjustment ........................................................................ 3

J. Power Adjustment ..........................................................................................4

2. CONTROL AND CONNECT LAYOUT ........................................ 7

A. Main PCB....................................................................................................... 7

b. Video PCB...................................................................................................... 8

C. Pin Assignment.............................................................................................. 9

...................... 2

3. POWER SUPPLY PORTION......................................................10

4. OPERATION THEOREM............................................................11

A. Introduction.................................................................................................... 11

B. Power Supply ................................................................................................. 11

C. Deflection.......................................................................................................11

D. Video............................................................................................................. 11

E. Digital Controller............................................................................................ 11

F. Function Block Diagram................................................................................. 12

5. POWER SUPPLY.......................................................................13

A. Rectifier and Filter CKT.................................................................................. 13

B. Flyback and PWM CKT.................................................................................. 13

C. Snubber CKT................................................................................................. 13

D. Synchronized CKT......................................................................................... 13

E. Power Saving CKT......................................................................................... 13

F. Degauss CKT................................................................................................. 13

G. Overload Protection CKT............................................................................... 13

H. Power Factor Correction CKT (Optional) .......................................................14

6. DEFLECTION.............................................................................16

A. SYNC Processor............................................................................................ 16

B. Hor. Processor & Vert. Pre- AMP................................................................... 16

C. Vertical Output............................................................................................... 16

D. Horizontal Driver Circuit................................................................................. 16

E. Horizontal Output Stage................................................................................. 16

F. Flyback Transformer ...................................................................................... 16

7. VIDEO AMP. CIRCUIT................................................................20

A. Video Pre. AMP ............................................................................................. 20

B. Video Amplifer................................................................................................20

8. TROUBLESHOOTING ................................................................22

A. Power Supply Check ...................................................................................... 22

B. Monitor Check Flow Chart.............................................................................. 23

APPENDIX A: PCB ASSEMBLY ..................................................24

APPENDIX B: DISPLAY UNIT ASSEMBLY .................................39

WARNING

1) This product contains components which are critical for X-radiation safety. Read the Service manual
carefully for proper replacement. Maximum 2nd anode voltage use high impedance meter, connect (-) to
chassis, use a high voltage lead from (+) to 2nd anode.

2) Critical Components are marked with the symbol of in the material list. For continued protection
against X-radiation, replace only with same type and rating components.

3) Critical Components are marked with the symbol of # in the material list. For continued protection
against Low Radiation, replace only with same part number.

4) This symbol warns the personnel that un-insulated voltage within the unit may have sufficient

Therefore, it should be read carefully in order to avoid any problems.

magnitude to cause electric shock.

1 DISPLAY ALIGNMENT

A. Times & Display Size

For all presetting mode listing in table 2 shall be within the limitation:
H. WIDTH 310 ± 3 mm
V. HEIGHT 233 ± 3 mm
The external control range of the data area, shall be as follows;
Max. horizontal size: overscan the screen
Min. horizontal size: ≤ 294mm
Max. vertical size : over the screen
Min. vertical size : ≤ 221 mm

B. Picture Position

For all presetting mode listing in table 2 shall be within the limitation:
H.PHASE SCREEN CENTER ± 3 mm
V.CENTER SCREEN CENTER ± 3 mm
The external control ranges of display for all modes listed in section 2.4
H.POSITION ≥ 50 mm
V.CENTER ≥ 25 mm

C. Linearity

The CONTRAST and BRIGHTNESS control shall be properly adjusted at 20 F-L with Full­intensity reverse pattern, then change to crosshatch Pattern 12x10 (H x V), the size of grid of
crosshatch pattern in every display mode shall not vary than 10%. If two line is next to each
other, 6% if they are not next to each other. The calculation formula was listed below:

H max - H min V max - V mi n
x100% or x 100%
(H max + H min) / 2 (V max + V min) / 2

D. Geometry Distortion (All Preset Mode)

1) The Contrast and Brightness control shall be properly adjusted at 25 F-L with full intensity

reverse pattern, then change to crosshatch pattern.

2) Pincushion distortion shall be less than H : 1.5% and V : 1.5%.

3) Ba rrel distortion shall be less than H : 1.5% and V : 1.5%.

4) Trapezoid and parallelogram distortion shall be less than H : 1.5% and V : 1.5%.

5) P a rallelogram distortion shall be less than 2.0%

6) Tilt distortion shall be less than 1/2 degree when facing east and less than 1 degree when turning

around 360 degree.

7) Tilt distortion shall be less than 2 mm when facing east and less than 1 degree when turning
around 360 degree. The measurement of tilt is defined to measure the vertical axis with respect
to the bezel, the absolute value of the difference between the extreme left and right
measurement of the center horizontal line.

1

E. Alignment Procedure

E-1. Brightness Adjust:

1) Adjust the VR980, have the +198VS By 198V± 0.2V (The voltage of the C949) in TIMING 1.

2) Check below items.

The voltage of C944 : 16 ± 1V

C947 : 75 ± 2V
C946 : -12.5 ± 1 V
C940 : 9.8 ± 1 V
C941 : 8.0 ± 0.5V

3) Short-Circuit protection function check.

! The power source is 230VAC input.
! When short the C949, all output voltage should be shut down and unlatch.
! When recover normal condition, all output voltage should recover automatically.

E-2. Light output adjust

! Select Timing 1, preset BRI. And CONT. to max. position.
! Adjust G2 to get G2 = 700V ± 10V
! Adjust VR803 to get light output = 0.3FL ~ 0.6FL

F. White Balance Adjustment (9300°as major temperature) Low light

adjust

9300° 6500° 5000°
x = 0.283 ± 10 x = 0.313 ± 10 x = 0.346 ± 10
y = 0.297 ± 10 y = 0.329 ± 10 y = 0.359 ± 10
Y = 0.3 ~ 0.6FL Y = 0.3 ~ 0.6FL Y = 0.3 ~ 0.6FL

1) Select Timing 6, adjust BRI. And CONT. to max. disconnect R. G. B. signals, adjust R/B
BAIS to 100 scale (OSD then slowly adjust G BAIS to 100 scale adjust VR803 to get light
output = 0.3 ~ 0.6FL for 9300, repeat above steps for 6500 and 5000 R/B GAIN setting to get
raster color temperature within specified, finally, adjust BRI to get raster = 0.06FL.

2) High light adjust

9300° 6500° 5000°
x = 0.283 ± 10 x = 0.313 ± 10 x = 0.346 ± 10

y = 0.297 ± 10 y = 0.329 ± 10 y = 0.359 ± 10
Y =46 FL Y =40 FL Y =40 FL

Select Timing 4, measure 2 "square, set CONT. to Max, position and SUB-CONT to 220, R/B
GAIN to 220, G GAIN to 230, adjust SUB-CONT to get light output = 46 FL for 9300,
repeat above steps for 6500 and 5000 R/B GAIN setting to get color temperature within
specified.

3) Select Timing 3 with full white pattern adjust OSD-ABL (SUB BRIGHTNESS) to get full
white light output = 30 +1/-0 FL.

-1
+2

-0
+5

-0
+5

-1

G. Focus Adjustment

G-1. Adjust brightness, have the brightness of raster be 0.06FL and contraset be max in

timming 6.

G-2. Adjust G5-1,G5-2 to get best focus.

2

H. Convergence Adjustment

Input R+B and R+G signals, make sure convergence within specified. A zone = 0.3MM., B
zone 0.4MM. (X) < 0.4MM, (Y) < 0.4MM, and x
NOTE : 1. A area = 233mm (circle)

2. B area = 310 x 233 mm
If not, readjust 4P and 6P on the deflection yoke to bet mis-convergence within specification.

2+y2

<0.45MM.

I. Presetting Modes Adjustment

There are totally 13 preset modes, individual adjust is needed.

1) H-SIZE adjust : adjust control key to get H-SIZE = 310 ± 3mm.

2) H-CENTER adjust : adjust control key to get center within ± 3mm

3) V-SIZE adjust : adjust control key to get V-SIZE = 233 ± 3mm

4) V-CENTER adjust : adjust control key to get center within ±3mm

5) Geometric adjust : adjust control key to get minimize distortion.

6) H-linearity check : check and make sure linearity meet spec..

(CROSS HATCH PATTERN 10X8)

MAX - MIN
X100%
MAX + MIN

Any : <5%
Adjacent : <4%

7) V-linearity check : check and make sure linearity meet spec.

MAX - MIN
X100%
MAX + MIN

Any : <5%
Adjacent : <4%

8) Geometric check : check and make sure geometric meet spec.

9) Get into OSD select EE-USER item, press ENTER till OSD disappear then turn off power,
disconnect JP1, turn on power again, make sure all of the alignment parameters has been
stored properly, make H-SIZE adjust range can OVER SCAN and -5%, PHASE adjust range
>15mm, V-SIZE adjust range can OVER SCAN and -6%, V-CENTER adjust range >20mm
and make sure TILT adjust work properly.

3

J. Power Adjustment

J-1. Adjust the VR901, have the +198Vs be 198±0.2v ( the voltage of the C949 ) in timing

1.

J-2. Check below items the voltage

C944 : 16 ± 1v
C947 : 75 ± 2v
C946 : -12.5 ± 1.5v
C940 : 9.8 ± 1v
C941 : 8.0 ± 1.0v

J-3. Short-circuit protection function check

1) the power source is 230vac input

2) when short the C949, all output voltage should be shut down and unlatch

3) when recover normal condition, all output voltage should recover automatically.

J-4. Side Pincushion, Tilt and Geometry Distortion Adjustment

1) Input timing 1, adjust the display be normal position and size.

2) Adjust front control key to get the best pincushion distortion and tilt.

J-5. Preset Timing Adjustment

1) Input each PRESET MODE timing, and use front control key adjust the display to the normal
position and size, and wait for 5 seconds.

2) Switch to next timing repeat 1 process. Until every PRESET MODE timing have been
adjusted.

J-6. Power Saving Function Check

1) The power source is 230Vac input

2) When remove the sync signal, the monitor should enter suspend mode and then off mode.

3) When power saving, the power consumption of monitor should be less than: suspend mode

8w off mode

4) The monitor recovering time from suspend mode or off mode to on mode should be less than
5 seconds.

TABLE 1

TIMING MODE PATTERN

1. 80K

2. 37.8K/60HZ

3. 80K Full-white

4. 80K

5. 80K “me”

6. 80K

51 CROSSHATCH
51 CROSSHATCH

5×2″squares

5×2″squares

4

TABLE2: PRESETING MODES

Mode

Factor

D:dot: D:display B: backporch P:plus F: front

H Pixes
L Lines

Fd(MHz)

Polar(H/V)

Fh (KHz)

Fv(Hz)

Th(us)

Tv(ms)

Td(us)

Td(ms)

Tb(us)

Tb(ms)

Tp(us)

Tp(ms)

Tf(us)
Tf(ms

1 VGA

IBM

2

VGA

3 VESA

IBM

4

VGA

5 VESA

6 VESA

VESA

7

XGA

8 VESA

640
350

640
480

640
480

720
400

800
600

800
600

1024

768

1024

768

25.175
P/N

25.175

N/N

31.5
N/N

28.321

N/N

40

N/P

56.25
P/P

65

P/P

78.75
P/P

31.469

70.087

31.469

59.940

37.5
75

31.468

70.085

37.879

60.317

53.674

85.061

48.363

60.004

60.023

75.029

31.778

14.268

31.778

16.683

26.667

13.333

31.778

70.085

37.879

60.317

18.631

11.756

20.677

16.666

16.66

13.328

25.422

11.122

25.422

15.253

20.317

12.8

25.422

12.711
20

15.84

14.222

11.179

15.754

15.88

13.003

12.795

1.907

1.875

1.907

1.0169

3.81

0.427

1.907

1.0804

2.2

0.607

2.702

0.503

2.462

0.6

2.235

0.466

3.813

0.064

3.813

0.064

2.032

0.08

3.813

0.064

3.2

0.106

1.138

0.056

2.092

0.124

1.219

0.05

0.636

1.207

0.636

0.318

0.508

0.027

0.636

0.413
1

0.026

0.569

0.019

0.203

0.017

0.203

0.017

9 VESA

10 VESA

VESA75

11

primary

12 VESA85

13 VESA75

1024

764

1280
1024

1280
1024

1280
1024

1600
1200

94.5
N/N

108

P/P

135

P/P

157.5
P/P

202.5
P/P

68.677

84.997

63.981

60.02

79.976

75.026

91.146

85.024

93.75
75

14.561

11.765

15.63

16.661

12.504

13.329

10.971

13.329

10.667

13.333

10.836

11.183

11.852

16.005

9.481

12.804

8.127

11.235

7.901

12.80

2.201

0.524

2.296

0.594

1.837

0.475

1.422

0.483

1.501

0.491

1.016

0.044

1.037

0.047

1.067

0.038

1.016

0.033

0.948

0.032

0.508

0.015

0.444

0.016

0.119

0.013

0.406

0.011

0.316

0.011

5

Fig. 1

Fig. 2

Fig. 3

6

7

2 CONTROL AND CONNECT LAYOUT

A. Main PCB

B. Video PCB

C. Pin Assignment

C-1. Connect Function

P701 : TILT, H Convergence, V Convergence CONN
JP1: PRESET CONN
P902 : DEGAUSSING COIL CONN
P730 : X-RAY TEST PAD

-- P302 P303 P301 P5 P2
1 G1 V-out DSUB9 D-SUB GND

2 GND EEP-SDA R-IN DDC-SCL
3 H-BLK EEP-SCL GND DDC-SDA LED2

4 5V CLAMP B-IN GND LED1
5 6.3V GND GND V-SYNC FUN
6 12V -- G-IN H-SYNC ADJ+
7 ABL -- GND -- ADJ­8 75V -- -- --

POWER
ON/OFF

9

10

3 Power Supply Portion

4 Operation Theorem

A. INTRODUCTION

D796 is a 17” multisync color monitor. The horizontal frequency range is from 30khz to 96khz,
and the refresh rate is from 50hz to 160hz. The circuit includes four major parts, the power
supply circuit, the deflection circuit, the video circuit and the digital control circuit. Fig. 1 is the
function bloc k diagram.

B. POWER SUPPLY

Transfer AC source to DC source that supply all the circuit power. It includes:

1) +16V: For video pre-amp circuit, parts of horizontal and vertical deflection circuit.

2) +198V: For deflection and H.V circuit

3) +8.0V: For CRT heater and u-P power.

4) +75V: For video AMP. Circuit.

5) -12V: For vertical flyback booster.

C. DEFLECTION

Produce YOKE deflection current of horizontal and vertical, CRT H.V and bias that makes
screen raster.

D. VIDEO

Amplify the video signal and add the signal to the cathode of CRT to produce video on the
screen.

E. DIGITAL CONTROLLER

With the EEPROM and PROGRAM, the micro-processor (u-P) controls all the picture
performance.
From the key control, the user can change the H-size, V-size, R-gain.…etc.

11

12

Fig .1

F. Function Block Diagram

5 POWER SUPPLY

A. RECTIFIER AND FILTER CKT

The 90Vac-260Vac input line voltage is rectified by D901-D904, and smoothed by C906 to
provide DC operating voltage for the circuit.

B. FLYBACK AND PWM CKT

When power is initially applied to the circuit, C909 charges through R903, Q905. When the
voltage across C909 reaches a level of 16V, U901 is enabled, turning on Q902 and turning off
Q905 to complete start-up action.
During the On-time of Q902, energy is stored in T902. At this time the polarity of the output
windings is such that all output rectifiers are reverse biased and no energy is transferred.
Primary current is sensed by R914 and R915 and compared to a DC level that is determined by
voltage feedback. When this level is reached, Q902 is turned off and the polarity of all T902
windings reverses, forward biasing the output rectifiers. All the energy stored is now transferred
to the output capacitors. Many cycles of this store/release action are needed to charge the
outputs to their respective voltages.
The main voltage (198V) across R944, R945, R946,VR901 is smoothed by C945 and by U900
photo cross to primary regulation to the error amplifier (U901 PIN1).

C. SNUBBER CKT

Energy stored in the leakage inductance of T902 cause a voltage spike which be added to the
normal reset voltage across T902 when Q902 turn off. The clamp consisting of D905, R904 and
C907 limits this voltage excursion from exceeding the Vds rating of Q902. In addition, a turn
off snubber made up of D906, R905 and C908 keeps power dissipation in Q902 low by delaying
the voltage rise until drain current has decreased from its peak value. This snubber also damps
out any ringing which may occur due to parasitic.

D. SYNCHRONIZED CKT

The oscillator frequency is defined by R912, C920. The equation is approximately:
Fosc=1.8/(R912*C920). The external signal “SYN+& SYN-“
That comes from horizontal circuit can synchronize the working frequency of power circuit Via
R997, C995 to U906(PIN 2). For divide frequency in over 50KHz by U906(74LS221)

E. POWER SAVING CKT

The monitor has ON, Suspend/Standby and OFF states. The monitor enters Suspend/Standby
mode if either V-sync or H-sync signals are removed. When the machine in the
Suspend/Standby state, PS1 should be low to turn off +16Vs. In this state, input power should
be less than 15W and LED illuminate yellow. The monitor enters OFF mode if both H-sync and
V-sync are removed. When in the OFF State, PS1 and PS2 should below simultaneously to turn
off +16Vs and +8.0Vs outputs. In this state, input power should be less than 5W and LED
illuminate amber.

F. DEGAUSS CKT

The DEGU signal which comes from micro-p to control degauss coil act or not.
When DEGU is high, Q946 will be saturated to make RL901 working, AC line provides a
degaussing current t o degauss coil.

G. OVERLOAD PROTECTION CKT

The primary current flows through the current sensi ng resistor R914 and R915. The voltage
drop on them will be rectified by D921 and keep a dc level in C921 that is dependent on the
output power. When this DC level reach the trigger voltage of Q912, the pin8 of U901 goes low
and the power stage is immediately switched off.

13

H. POWER FACTOR CORRECTION CKT (OPTIONAL)

PFC CKT is inserted between the rectifier bridge (D901-D904) and C906, U991A (MC33260)
drives the switching MOSFET, Q901A, is working as a free running, discontinuous voltage
mode. This control way named “ follower boost”
Connecting three resistors (R906A, R907A & R908A) between C906 and U991A pin1, to
obtain a feedback current. The feedback current is compared to the reference current so that the
regulation block outputs a DC level at pin 1 to determine the output voltage of C906.
The output voltage of C906 is varied linearly versus the AC line amplitude.

14

15

6 DEFLECTION

A. SYNC PROCESSOR

H-sync & V-sync or input to U1 (u-P), then u-P output the H-out & V-out to U401 (TDA4856).

B. HOR. PROCESSOR & VERT. PRE-AMP

Fig.2 is the block diagram of IC TDA4856.

Hor. processor

The H-out that come from u-P will input to the pin 15 of U401, it will be compared with the
oscillator sawtooth voltage by the PLL1 (pin 26) phase detector, After that, it will be compared
again with the flyback pulse (pin 1) by the PLL2. The PLL2 detector thus compensates for the
delay in the external horizontal deflection circuit by adjusting the phase of the HDRV (pin 8)
output pulse.

+B

control

The U401 pin 5 to pin 3 is operation Amplifier from pin 11 EW DRV parabola amplitude DC, H­Size and Trapezium correction wave from connection, pin 6 is forward PWM output, driver the
Q420, Q422 all mode +B is 198V

Vert. Pre-amp

Vertical oscillator will be trigged by V-out (pin 14). It is available to get sawtooth waveform in
pin 24. V-center, V-amp and V-linearity can be adjusted by I
output driver is come from pin 12 and 13.

2

C bus from U1. The vertical

C. VERTICAL OUTPUT

IC U601 (TDA4863A) is the vertical amp IC, the output pin 5 connect to the YOKE .The
sawtooth current float across the YOKE to make vertical deflection. Fig.3 is the block diagram
of IC TDA4863A

D. HORIZONTAL DRIVER CIRCUIT

The driver pulse that come from U401 pin 8 drive Q417, Q416, TO Q503,then transformer T501
convert driver pulse to driver current to drive horizontal output transistor Q504.

16

E. HORIZONTAL OUTPUT STAGE

C541
C511
C520 C521 C519 C525

sw

fh

30~32.9k L L L L → Cs=C511+C541+C520+C521C+C519+C525
33~35.9k H H L L
36~39.9k L H L H
40~44.9k H H L H
45~50.9k L L H L
51~54.9k L H H L
55~57.9k H H H L
58~61.9k H H H L
62~65.9k L L H H
66~70.9k H L H H
71~83.9k L H H H

84~above H H H H →Cs=C511+C541

sw1 sw2 sw3 sw4

F. FLYBACK TRANSFORMER

In the primary of F.B.T, there is about 700Vpp in the LC resonant interval,
It convert to the secondary of F.B.T to produce about 25KV for CRT anode voltage.
The other bias for CRT IS G4.G3 (4∼8KV),G2(0∼1000V)and G1(-170V)

17

18

Fig. 2

Autosync Deflection Controller ASDC - TDA4855/TDA4858

BLOCK DIAGRAM

Vertical Deflection Booster TDA4863; TDA4863A

Fig. 3

19

7 VIDEO AMP. CIRCUIT

A. VIDEO PRE. AMP.

The video pre-amp IC is U301 (M52743). The input signal is 0.7Vpp, then pre-amp IC U301
amplify the video signal to 4~5Vpp. The WHITE BALANCE and CONTRAST can be adjusted
internal by I

B. VIDEO AMPLIFIER

The video amplifier is U303 (LM2435), it amplify video signal to about 40Vpp. Video output
signal add to cathode by AC coupling. The DC bias is controlled by the output pwm of IC U302.
Fig.5 is the block diagram

BLOCK DIAGRAM

2

C bus. Fig.4 is the block diagram.

M52743SP Block Diagram

Fig .4

20

LM2435

Simplified Schematic Diagram

(One Channel)

Fig. 5

21

8 TROUBLESHOOTING

A. Power Supply Check

22

B. Monitor Check Flow Chart

23

APPENDIX: A PCB ASSEMBLY

24

THE UPDATED PARTS LIST

FOR THIS MODEL IS

AVAILABLE ON ESTA

APPENDIX B: DISPLAY UNIT ASSEMBLY

39

40

Top Assembly - MD796

FOR MECHANICAL

43

For Electrons MPRII (Mitsubishi CRT)

44

For Mechanical TCO99

45

For Electrons TCO99 (Mitsubishi CRT)

46

NOTE: ITEM WITHOUT DRAWING

49

CRT & YOKE Assembly - MD796

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