Toshiba CF35E50, Техническое учебное пособие

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3. IF/MTS/S.PRO MODULE
The IF/MTS/S.PRO module (MVUS34S) limits bandwidth
of IF signals and detects video and audio signals. The module
consists of IF amplifiers, SAW (surface acoustic wave)
filter, and PIF IC. The SAW filter has a wideband response
to improve picture quality and audio buzz characteristic and,
develops separate outputs of video and audio signals. The
PIF IC employs a PLL complete sync det audio split
carrier system.
3-1. IF/MTS/S.PRO Module (MVUS34S)
3-1-1. Module Terminal Layout
3-1-2 Video PIF Circuit
A PIF detector switching carrier is oscillating at a frequency
adjusted to 45.75 MHz with L051 (VCO CW coil) under no
RF signal input. When an RF signal enters, an IF video
carrier is fed to APC section from IF AMP inside the IC, and
the detector switching carrier is adjusted by the APC, VCO,
etc. in the PLL circuit so that its frequency and phase are
matched to those of the IF video carrier to perform precise
sync detection. Thus processed video output is developed at
pin 21.
PLL lock speed is automatically controlled by adding the
video signal at pin 21 to pin 1. That is, since the video signal
is not output at operations of power on, CH switching, etc.,
the APC filter between pin 16 and GND consists of C022 and
C053, and R018, and the filter effect decreases, thus increasing
PLL lock speed.
Next, when a video out exists, the internal resistance is short-
circuited and the APC filter consists of C022 and C053,
internal resistance, and R018. As a result, the filter effect
increases and the PLL lock speed decreases. Consequently,
under normal signal reception, phase of the detector switching
carrier is locked in a stable condition if an IF video carrier is
lost for a short time due to over modulation, etc. By combining
such a PLL complete sync detection system and a wideband
SAW filter shown in Fig. 2-4, a wideband (4.2 MHz) video
detection output with less beat interference will be obtained.
3-1-3. Audio PIF Circuit
The IF signal fed through Q003 (Fig. 2-4) enters an audio
section of the SAW filter (Z001) which has an IF bandwidth
for dedicated audio signals, and only the audio signal of
41.25 MHz is fed to pin 7. The signal is sync-detected with
the detection carrier completely synchronized with the IF
video carrier and pin 14 develops a 4.5 MHz SIF signal. By
using the PLL split carrier system just stated, audio signals
with less buzz by the video signal will be reproduced. The 4.5
MHz SIF enters pin 15 through a 4.5 MHz filter, Z003 and
pin 9 develops a FM-detected audio signal.
Pin No. Name Pin No. Name
1 GND 15 DAC-OUT2
2 IF-IN 16 R-IN
3 NC 17 C-IN
4 +9V 18 L-IN
5 RF AGC 19 GND
6 AFC 20 SCL
7 VIDEO OUT 21 SDA
8 ADR SW 22 W-OUT
9 MPX OUT 23 C-OUT
10 --- 24 L-OUT
11 --- 25 GND
12 TV R-OUT 26 R-OUT
13 DAC-OUT1 27 +9V
14 TV L-OUT
Fig. 2-3 IF/MTS/S.PRO module terminal layout
27 12
9 1