Akai VS-2EGN

2-2-2 PLAYBACK OF PAL B/G AND NTSC 4.43
(CHROMA) SIGNALS
The PB video signal (low frequency converted CHROMA
+ FMY) from the Pre-amp Board passes through PRE
OUT Inter-Board Connection to the Video Board and
then to the LPF of FL12 (1.5 MHz at —3 dB), and is fed
to IC10 pin having only the CHROMA component
remaining. This signal passes through the ACC (Auto
Colour Control) in IC10 at the time of PB mode, is re-
input from pin (7) to pin (1 , and converted to the
original CHROMA signal at the balanced modulator by
means of the 5.06 MHz carrier supplied to pin (4). The
output from pin (3), passes through the BPF FL13
(4500 kHz of 4.43 MHz at —3 dB), enters pin (Q as
4.43 MHz CHROMA signal, and is output from pin @)
via the amplifier.
1) Operation during the PAL mode
Regarding the CHROMA signal from IC10 pin ©, since
the DIRECT PASS component and the 2H DELAY com-
3) PB APC system
ponent are mixed in DL2 (PAL 2H delay line), the cross-
talk component is cancelled. The cancelled crosstalk
component passes through TR55 (due to NT-H line
being ‘L’), enters IC10 pin ©, goes out from pin iO)
through internal switch, level-adjusted at VR13, and
enters IC6 pin ©.
2) Operation during the NTSC 4.43 mode
Since the 4N-H line is ‘H’, D31 becomes ON, TR54
becomes ON, the emitter of TR55 is reverse-biased, the
stroke component is cancelled at DL3 (NTSC 1H delay
line), and the output from IC10 pin ® enters IC10 pin
©. During recording, the BURST signal amplified by
6 dB is now attenuated by 6 dB during playback. The
CHROMA signal fed to IC6 (HA11703) pin © is mixed
with PBY, and the combined output passes to VIDEO
OUT along the same route as the aforementioned E-E
system.
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The 5.06 MHz signal to be supplied to IC10 pin (@.
The PB low frequency CHROMA signal: supplied to
pin (te) is amplitude/frequency modulated due to un-
even rotation of the tape driving system and uneven
rotation of the mechanism system. When this modu-
lated CHROMA signal is directly transformed to a nor-
x1
4.4336 19MH2
‘Service Manual VS-2EGN
if
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NTSC TR47 eee |
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629.37056KHz
1H = 15625Hz (PAL BG)
tH'=15734.264Hz (NTSC)
Fig. 7-10 PB APC Block Diagram
mal CHROMA signal which is then fed to the TV set,
hue changes and a picture with changing degrees of
saturation will result. Accordingly, the amplitude modu-
lated component is removed by passing the CHROMA
signal through the ACC circuit, and the frequency modu-
lated component is removed at the APC circuit.
19