Hitachi CMT2988-981 User manual

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CMT2988
-051
SERVICE
MANUAL
-081
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CAUTION:
Before
servicing
this
chassis,
it
is
important
that
the
service
technician
read
the
‘Safety
Precau-
tion”
and
“Product
Safety
Notices”
in
this
service
Manual.
BR
CONTENTS
ABUZZ
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Safety
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Product
safety
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Technical
cautions
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3
Technical
specifications
.......sserrrerees
6
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tees
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3
Main
features
..........:..ceseeeeneeeeeeeereseeees
6
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4
Names
of
controls
........essecccesseeseeseeeeees
7
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4
Remote
control
unit
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7
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8
Wiring
diagram
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8
FRAC
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11
Basic
circuit
diagram
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20
Printed
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board
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20
PR
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95
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Replacement
parts
list...........cseeeseereeeee
25
ARERR,
RASERANS
ALR
RM.
SPECIFICATIONS
AND
PARTS
ARE
SUBJECT
TO
CHANGE
FOR
IMPROVEMENT
5 Bite
COLOUR
TELEVISION
September
1992
Consumer
Electronics
Division

CMT2988
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SAFETY PRECAUTIONS
WARNING: Since the chassis of this receiver is connected
to one side of the Mains Supply during operation, service
should not be attempted by anyone unfamiliar with the
precautions necessary when working on this type of
equipment. The following precautions should be observed.
1. Do not install, remove, or handle the picture tube in any
manner unless shatter-proof goggles are worn. People
not so equipped should be kept away while picture tubes
are handied. Keep picture tube away from the body while
handling.
2. When replacing chassis in the cabinet, all the protective
devices are put back in place, such as; barriers, non-
metallic knobs, adjustment and compartment cover or
shields, isolation resistors-capacitors, etc.
3. When service is required, observe the oritinal lead dress.
Extra care should be taken no assure correct lead dress in
the high voitage circuitry area.
4, Always use the manufacturer's replacement component.
Especially critical components as indicated on the circuit
diagram should not be replaced by other makes.
Furthermore where a short circuit has occurred, replace
those components that indicate evidence of overheating.
5. Before returning a serviced receiver to the customer, the
service technician must thoroughtly test the unit to be
certain that it is completely safe to operate without
danger of electrical shock, and be sure that no protective
device built into the instrument by the manufacturer has
become defective, or inadvertenly defeated during
servicing.
Therefore, the following checks are recommended for the
continued protection of the customers and_ service
technicians.
INSULATION
Insulation resistance between the mains poles and any
accessible metal parts should not be less than 7MQ. at 500V
DC. Also, no flashover or breakdown should occur during
the dielectric strength test, to apply 4KV AC for one minute
between the mains poles and any accessible metal parts.
X-RADIATION
TUBES: The primary source of X radiation in this receiver is
the picture tube. The tube utilized in this chassis is specially
constructed to limit X radiation.
For continued X radiation protection, the replacement tube
must be the same type as the original, HITACHI approved
type.
CMT298&
High Voltage
This receiver is provided with a hold down circuit for
clearly indicating that voltage has increased in excess of a
predetermined value. Comply with all notes described in
this Service Manual regarding this hold down circuit when
servicing, so that this hoid down circuit is operated
correctly.
Serviceman warning
With minimum Black Level and Picture, the operating high
voltage in this receiver is lower than 31.5kV. In case any
component having influence on the high voltage is
replaced, confirm that high voltage with minimum
Brightness and contrast is lower than 31.5kV.
To measure H.V. use a high impedance H.V. meter.
Connect (—) to chassis earth and (+) to the CRT anode
button. (See the following connection diagram).
NOTE: Turn the power switch off without fail before the
connection to the Anode button is made.
CRT ANODE
HIGH IMPEDANCE
H.V. METER
CHASSIS GROUND
PRODUCT SAFETY NOTICE
Many electrical and mechanical parts in HITACHI television
receiver have speciai safety related characteristics. These
characteristics are often not evident from visual inspection
nor can be 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 in this Service
Manual. Electrical components having such features are
identified by marking with a A\ mark in the schematics and
on the replacement parts fist in this Service manual. The use
of a substitute replacement component which. does not have
the same safety characteristics as the HITACHI recom-
mended replacement one shown in the parts list in this
Service Manual, may create electrical shock, fire, X
radiation, or other hazards.
Product Safety is continuously under review and new
instructions are issued from time to time. For the latest
information, always consult the current HITACHI Service
Manual. A subscription to, or additional copies of, HITACHI
Service Manuai may be obtained at a nominal charge from
your HITACH! SALES CORPORATION.

SMT2988
TECHNICAL CAUTIONS
High voltage limiter circuit. operation check
1.
2.
anode (anode cap) and GND (CPT grounding lead).
Receive the broadcast signal and set the brightness and
contrast VRs to max. Set the beam current to 1.15mA
10% :CMT2528 1.45mA+10% : CMT2928
(After cut-off adjustment)
. Set the AC input voltage to 132-13V.
. Check that the constant high voltage is 28.7£1.0kV at this
time.
. Turn the switch of the set to off and connect the jig shown
in Fig. 3 at both ends of R971 as shown in Fig. 1.
Power Supply P.W.B.
CPT Earth Wire
Connect the high voltage voltmeter between the CPT
D.C Voltage Divide
6. With the brightness and contrast VRs left as set in item 2
and with the AC input voltage stabilized at 132V, turn the
set on and increase input voltage and check that the
picture disappears with a high voltage of 35.0kV or less.
7. Turn the switch of the set to off immediately after the
check is completed.
8. Remove the adjust jigs and high voltage voltmeter.
Note: When connecting disconnecting the high voltage
voltmeter to from the anode cap, be sure to turn the
switch of the set off and do it after the residual high
voltage is discharged to the chassis because the high
voltage may remain at the. anode cap.
eo—_w—e
R969 vrgs1
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Fig. 1
15KQ
50KO-B
Jig
Digital Voltmeter
Fig. 3
Specifications
B.G/I/D.K/H_ PAL
B.G/D.K/K’ SECAM
NTSC50
M/NTSC
NTSC3.58-5.5/6.0/6.5
NTSC4.43-5.5/6.0/6.5
PAL60
625-lines
Reception system | 525-lines
Hong Kong, U.K. : UK21~69
China :C1~12, C13~57
CCIR :E2~12, E21~69,
01~3, S1~10, S11~20
Channel coverage |OIRT :<R1~12, R21~69
- {Frequency range JAPAN : J1~12, J13 ~62
hea U.S.A. > US2~13, J~W,
470MHz~863MHz US14~69
Aerial input
Color picture tube
75Q unbalanced type
A68KRT370X
13cm X6cem(X 2)
12cmX6em(X 1)
6cm X 4cm(X 2)
12WX2+10W
AC110V/127V/220V 50/60Hz
AC220V—240V 50/60Hz .
(—081 only)
Speaker
Sound output
Power supply
180W
45.0
Power consumption
Weight (kg)
Dimensions
WXHXD (cm)
Country of manufacture
76.0X59.0X49.5
Japan
* Specifications are subject to change without notice to improve performance.
Main Features
1. Advanced full function remote control system
2. Front video input terminals

CMT2988
Names of controls
7
Program up/down button
2
13 | External speaker select switch
AV IN/OUT terminals
Remote control transmitter
Power ON/OFF Input select
2 Programme selecter
Dynamic noise Program up/down
A reduction 15 | Mute
i 16 | Volume up/down
B al
Cc
D
E
2 Sound mode
F TV/VTR select
: Exclusive VTR buttons
; ra A~N shows the key function in Teletext mode.
7
O, P_ shows the key function in Sound
multiplex mode.

CMT2988
H im
WIRING DIAGRAM
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that the wires do not touch the terminals of the power
ihe 7S BU UB 9 SAG cuaak.
Aa RES ana] Le AS Be EBL A Perform wiring without touching the heat sink.
174 P M Bea a8 7 BR Perform wiring along the PM connector.

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