CIRCUIT DESCRIPTION
1. POWER SUPPLYchroma signals, demodulated in IC201, and output from
The power supply circuit of the EB4-A chassis ispin30 (R-Y) and pin31 (B-Y). These chroma signals pass
composed of a rectifier smoothing circuit, an oscillationthrough the 1H delay line circuit (IC271), and they are
circuit, a control circuit and an output rectifier circuit. Theinput to pin29 (R-Y) and pin28 (B-Y). These R-Y/B-Y
AC input voltage is full-wave rectified by the rectifiersignals pass through RGB matrix circuit and RGB
smoothing circuit, and an unstable DC voltage isselector circuit of IC101. The internal RGB signals are
generated at both terminals of the smoothing capacitorgenerated in RGB matrix circuit and the RGB selector,
C607. This voltage is input to the oscillation circuit. Theconsisting linear amplifiers, clamps and selects either the
oscillation circuit is provided with a blocking oscillatorinternal RGB signals or the external RGB signals input
circuit that switches the switching transistor Q613 ONfrom pin22(R), pin23(G), pin24(B). Selection is controlled
and OFF, and an oscillation frequency and a duty squareby the voltage at the RGB switch control (pin21) and
wave pulse are generated in the input windingsmixed RGB modes are possible since RGB switching is
according to operation of the control circuit. A square-fast. The RGB switch also functions as a fast blanking
wave pulse whose size is dependent on the turn ratio ofpin by blanking the RGB output stages; here internal and
the input and output windings is obtained in the outputexternal RGB signals are overruled. The colour gain is
winding. This is rectified in the output rectifier circuit, andcontrolled by DC voltage of pin26. (OCOLOUR� control)
the desired DC voltage is obtained.The contrast control voltage present at pin25, and the
brightness control voltage present at pin17 controls DC
2. IF & DEFLECTION (TDA8361)level of RGB signals. The RGB signals are finally
The IF output signal from the tuner passes through thebuffered before being available at the RGB output pins
SAW filter, and it is input to pin45 and pin46 of IC201.[pin20 (R), pin19 (G), pin18 (R)].
The signal input to the IC passes through the IF
amplifier, video detection and video amplifier circuits and4. AUDIO OUTPUT(TDA7263M)
is output from pin7 as a composite video signal. AndThe audio signals output from the audio unit are input to
after this signal is converted to impedance at Q151,pin1(L) and 5(R) of IC171 and passes through the pre-
supplies to the video and chroma amplifier stages. amplifier circuit and drive circuit, after which it is input to
The sync.-separation circuit separates the video signalsthe audio amplifier. The audio amplifier is an SEPP
applied to pin13(internal video signal) or pin15(external(single-ended, push-pull) OTL type and output to pin8(R)
video signal) to vertical- and horizontal-sync. signalsand 10(L) to directly drive the speakers.
respectively. The horizontal oscillator requires no
external components and is fully integrated. The5. VERTICAL OUTPUT (LA7832/LA7832)
oscillator is always running when the start-pin36 isAn IC (LA7832/LA7833) is used for the vertical output
supplied with 8V. Horizontal drive signal is output fromcircuit in this chassis. The vertical drive pulse from pin43
pin37. VR361 is for adjustment of the horizontal centring.of IC201 is input to pin4 of IC501. This pulse drives
The separated vertical-sync. signal from sync. separationIC501, and vertical scanning is performed. In the first half
circuit passes through the vertical-separation circuit, andof scanning a deflecting current is output from pin2 and
applied to trigger divider circuit. The horizontal oscillationpasses through the following path:
pulse and input vertical sync. pulse are monitored by theVcc(B4) Ţ D501 Ţ pin3 Ţ pin2 Ţ DY Ţ C512 Ţ
trigger divider circuit, and switching 50Hz and 60HzVR501/R509. An electric charge is then stored in C512.
system, the vertical amplitude automatically adjusted forIn the last half of scanning the current path is C512 Ţ
50Hz and 60Hz. The output signal from the triggerDY Ţ pin2 Ţ pin1 Ţ VR501/R509 Ţ C512. In this way,
divider is triggered vertical oscillation circuit consisting of
C351, R352 and pin42, and vertical drive pulse is outputan amplifying sawtooth waveform current flows directly to
DY to perform electron beam defection. Next, in the first
from pin43. VR501 is for changing the amount of AChalf of the banking period the vertical drive pulse
feedback applied to pin41 and for adjustment of thesuddenly becomes OFF, and in order to reduce the
vertical amplitude. current flowing to DY, the current path becomes as
3. VIDEO CHROMA & R.G.B. (TDA8361)follows by the inductance of DY:
DY Ţ pin2 Ţ pin1 Ţ VR501/R509 Ţ C512 Ţ DY. Also,
The composite video signal output from the pin7 ofwhen the charge of DY has dissipated, the current path
IC101 passes through Q151-Q154, and it is supplied tobecomes Vcc24V Ţ pin6 Ţ pin7 Ţ C502 Ţ pin3 Ţ
pin13. The external video signal output from SCART is
supplied to pin15. The video signal input to pin13 orpin2Ţ DY Ţ C512 Ţ VR501/R509, and when the
pin15 is separated to luminance (Y) signal and chromaprescribed current value is reached, the vertical drive
pulse becomes ON. This completes one cycle.
signal in IC201. These pins are used in common with
H/V-sync. separation input. The peaking of Y signal is
adjusted by DC voltage of pin14. (OSHARPNESS�
control) The chroma signal is divided into R-Y and B-Y
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F7JGV |
ACEC
