Sanyo Denki C20ZE70 User manual

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SERVICE MANUAL
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IFILE NO.
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Colour Television Model No. C20ZE70
(New Zealand)
Service Ref. No. C20ZE70- 00
Specifications
Power Source .................... AC220- 240Volts, 50 Hz.
Colour &Television
System ....................pAL-fYG
Channel Coverage .............VHF: 1-11
UHF: 21-69
Video IF............................. 38.9 MHz
Sound IF............................ 33.4 MHz
Aerial Input Impedance ...... 75 S2
Ext. Terminals, ................... Video input (Phono jack x1)
Audio input (Phono jack x1)
Video output (Phono jack x1)
Audio output (Phono jack x1)
Sound Output .....................3.5W
(music)
Dimensions ........................ 494(W)x442(H)x472 (D)mm
Weight ...............................approx. 17.5Kg
Specifications subject to change without notice.
Product Code: 111322219
Original Version
Chassis Series: A7-A
I
Give complete “SERVICE REF. No.” for parts
order or servicing. It is shown on the rating plate
at the cabinet back of the unit.
G
This T.V. receiver will not work properly in
foreign countries where the television trans -
mission system and power source differ from the
E8HZ REFERENCE NO. SM 520128

Block Diagram
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–2–

Block Diagram
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ICI 01 (TDA8362
&ASI
(D106)
NTSC
Band Limited
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Fin Vin
TvOut
SECAM
REF.
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CHROMA ID
NID.
(TIME BASE)
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.......
6.5 MHz Filter ~>
S11
(Q156)
.......
6.OMHZ Filter ~-
Slo
(Q155)
-------
5.5MH2 Filter
—~k- S9
(Q154)
.......
4.5 MHz Filter
~>
SIF Filter S8
(Q153)
+........... S2 5.5 MHz Trap
i(D120)
ifl~ 4.5 MHz Trap I
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................................................
,:
IC701 (CPU) \:.
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20 SECAM1 44--~
+CID. :,
SECAM2 ?:----------------] -----:
sTV ID. 4.5 :!----------------+
5.5 -~g-----------, :
-?-? 4.43
-4! 3.58
50/60 ID,
2
V-SYNC. Pulse
(for O.S. D.)
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–3–

Circuit Description
1.POWER SUPPLY
The power supply circuit of the A7 -Achassis is
composed of arectifier smoothing circuit, an oscillation
circuit, acontrol circuit and an output rectifier circuit.
The AC input voltage is full- wave rectified by the rectifier
smoothing circuit, and an unstable DC voltage is
generated at both terminals of the smoothing capacitor
C507. This voltage is input to the oscillation circuit. The
oscillation circuit is provided with ablocking oscillator
circuit that switches the switching transistor Q513 ON and
OFF, and an oscillation frequency and a duty square
wave pulse are generated in the input windings according
to operation of the control circuit. Asquare- wave pulse
whose size is dependent on the turn ratio of the input and
output windings is obtained in the output winding. This is
rectified in the output rectifier circuit, and the desired DC
voltage is obtained.
2.IF &DEFLECTION
The IF output signal from the tuner passes through the
SAW filter, and it is input to pin45 and pin46 of ICI 01.
The signal input to the IC passes through the IF amplifier,
video detection and video amplifier circuits and is output
from pin7 as acomposite video signal.
And after this signal is converted to impedance at Q124,
supplies to the video and chroma amplifier stages passed
through the AV switching circuit of IC290.
The output signal from pin7 passes through the
5.5 MHz(B/G)/6.0MHz( l)/6.5MHz(D/K)/4 .5MHz(M) filtering
circuit, and it is input to pin5 of IC101. The signal input to
the IC passes through the SIF amplifier, FM detector,
external audio switch and audio output circuit, and it is
then output from pin50 as audio drive signal.
The sync. -separation circuit separates the video signals
applied to pin13 or pin15 to vertical- and horizontal-sync.
signals respectively.
The horizontal oscillator requires no external components
and is fully integrated. The oscillator is always running
when the start- pin36 is supplied with 8V.
Horizontal drive signal is output from pin37. VR401 is for
adjustment of the horizontal centering.
The separated vertical sync. signal from sync. separation
circuit passes through the vertical -separation circuit, and
applied to trigger divider circuit.
The horizontal oscillation pulse and input vertical sync.
pulse are monitored by the trigger divider circuit, and
switching 50Hz and 60Hz system, the vertical amplitude
automatically adjusted for 50Hz and 60Hz.
The output signal from the trigger divider is triggered
vertical oscillation circuit consisting of R401 ,C402 and
pin42, and vertical drive pulse is output from pin43.
VR451 is for changing the amount of AC feedback applied
to pin41 and for adjustment of the vertical amplitude.
3.VIDEO CHROMA
The composite video signal output from the pin7 of IC101
passes through Q122/ Q124, and it is supplied to pin13.
The external video signal output from SCART or other AV
terminal passes through IC290, and it is supplied to pin15.
The video signal input to pin13 or pin15 is separated to
luminance (Y) signal and chroma signal in IC101. These
pins are used in common with H/V -sync. separation
input.
The peaking of Ysignal is adjusted by DC voltage of
pin14.(’’SHARPN ESS” control)
The chroma signal is divided into R-Y, B-Ychroma
signals, demodulated in IC101,
and output from pin30 (R -Y) and pin31 (B -Y). These
chroma signals pass through the 1Hdelay line circuit
(IC270), and they are input to pin29 (R-Y) and pin28 (B-
Y). These R- Y/B- Ysignals pass through RGB matrix
circuit and RGB selector circuit of IC101. The internal
RGB signals are generated in RGB matrix circuit and the –
RGB selector, consisting linear amplifiers, clamps and
selects either the internal RGB signals or the external
RGB signals input from pin22 (R) ,pin23 (G), pin24 (B).
Selection is controlled by the voltage at the RGB switch
control (pin21 )and mixed RGB modes are possible since
RGB switching is fast.
The RGB switch also functions as afast blanking pin by
blanking the RGB output stages; here internal and
external RGB signals are overruled.
The colour gain is controlled by DC voltage of pin26.
(“COLOUR” control)
The contrast control voltage present at pin25, controls the
RGB signal gain, and the brightness control voltage
present at pinl 7controls DC level of RGB signals.
The RGB signals are finally buffered before being
available at the RGB output pins [pin20 (R), pin19 (G),
pin18 (B)].
4.AUDIO OUTPUT
The audio signal output from pin50 of IC101 is input to
pin2ofIC171 and passes through the pre -amplifier circuit
and drive circuit, after which it is input to the audio .
amplifier. The audio amplifier is an SEPP (Single- Ended
Push Pull) type and output to pin8 to directly drive the
speaker.
–4–

Circuit Description
5.VERTICAL OUTPUT
An IC (IA7832) is used for the vertical output circuit in this
chassis. The vettical drive pulse from pin43 of ICI 01 is
input to pin4 of IC451. This pulse drives IC451, and
vertical scanning is performed. In the first half of scanning
adeflecting current is output from pin2 and passes
through the following path:
VCC(B4) +D451 +pin3 +pin2 +DY +C461 +
VR451 IR459.
An electric charge is then stored in C461. In the last half of
scanning the current path is:
C461 +DY =b pin2 * pinl +VR451/R459 +C461
In this way, an amplifying sawtooth waveform current
flows directly to DY to perform electron beam deflection.
Next, in the first half of the blanking period the vertical
drive pulse suddenly becomes OFF, and in order to
reduce the current flowing to DY, the current path
becomes as follows by the inductance of DY:
DY +pin2 +pinl +VR451/R459 +C461 +DY
Also, when the charge of DY has dissipated, the current
path becomes:
Vcc+ pin6+ pin7+ C452+ pin3+ pin2+ DY+ C461 +
VR4511R459
and when the prescribed current value is reached, the
vertical drive pulse becomes ON. This completes one
cycle.
6.HORIZONTAL OUTPUT
Ahorizontal oscillation signal is output from pin37 of
IC101 and switches the drive transistor Q431. This
switching signal is current amplified by the drive
transformer T431 and drives the output transistor Q432.
When Q432 becomes ON, an amplifying current flows
directly to DY through
C441/C442 @L441 /R441 +DY +Q432- C+Q432- E
and deflection is performed in the last half of the scanning
period. Next, when Q432 becomes OFF, the charge that
had been stored in DY up to that point releases a
resonance current to the resonant capacitors C435 and
C436 and charges them. The current stored in C435 and
C436 is then flowed back to DY, and an opposite charge
is then stored in DY. This opposite charge then switches
the dumper diode in Q432 ON, the resonance state is
completed, and an amplifying current is then flowed again
directly to DY through the dumper diode.
By this means, deflection in the first half of the scanning
period is performed ,and when Q432 becomes ON at the
end of the first half of the scanning period, deflection
during the last half is begun, thus completing one cycle.
7. SYSTEM SWITCHING
(For multi- standard model)
The system switches (S1 -S11 )are used for multi -
standard model.
(Refer to Block Diagram of system switching circuit)
S1:Switch for band-limiting on NTSC(3.58) mode (D106)
This switch is driven by ON/OFF signal of CPU
(pin40).
S2:Switch for sound carrier trap on NTSC(3.58) mode
(D120)
This switch is driven by signal of CPU (pin40) too.
S3:Switch for sound carrier trap except NTSC(3.58) mode
(D121)
This switch is driven by inverting signal of
(pin40).
S4:System switch for forced SECAM mode (Q203)
This switch is driven by ON/OFF signal of
(pin44).
CPU
CPU
S5: Input switch for SECAM colour demodulation (IC290)
This switch is driven by ON/OFF signal of CPU
(pin41).
S6:System switch for forced 4.43 mode (Q222)
This switch is driven by ON/OFF signal of CPU
(pin43).
Note: When the colour system is set to “AUTO, both S6
and S7 will turn on.
S7:System switch for forced 3.58 mode (Q221 )
This switch is
(pin42).
S8:System switch
mode (Ql 53)
This switch is
(pin40).
S9:System switch
(Q154)
This switch is
(pin39).
driven by ON/OFF
for 4.5 MHz filtering
driven by ON/OFF
for 5.5MHz filtering
driven by ON/OFF
signal of CPU
on NTSC(3.58)
signal of CPU
on B/G mode
signal of CPU
SIO:System switch for 6.OMHZ filtering on Imode (QI 55)
This switch is driven by ON/OFF signal of CPU
(pin38).
S11:System switch for 6.5 MHz filtering on D/K mode
(Ql 56)
This switch is driven by ON/OFF signal of CPU
(pin37).
Note: When the TV system is set to “AUTO”, S8, S9, S1O
and S11 will turn on.
–5–