SR23 - 923-03509 3-2 CS - SERVICING
CIRCUIT OVERVIEW (continued)
INTEGRATED CIRCUITS
ICX2201 is a chroma decoder. It receives luminance and
chroma signals and decodes them to YUV video with
synchrony. The diagram shows the connections of the
luminance signal to the synchrony inputs. This is
because the chip extracts the horizontal and vertical
sync pulses from the luminance composite sync.
The YUV video and sync from the ICX2201 are fed to
the ICX2200 at pins 5 (IN2-3), 4 (IN2-2), 3 (IN2-1), 1
(IN2-H), and 2 (IN2-V).
The ICX2200 is an RGB video processor and switch that
supports multi-scan capabilities. This switch has four
inputs:
• IN2 (pins 1-5): This input is used for the YUV
video from ICX2201. It is selected by the
microprocessor whenever the set is in NTSC
mode by setting the input-SEL register to 0.
• IN3 (pins 7-11): This input is connected to
the rear jackpack through connector 8VGA2.
When this input is selected the microprocessor
sets the input-SEL register to 1.
• IN4 (pins 13-17): This input is connected to
the front jackpack connector 6F1 located in
front of the set. The microprocessor selects it
by setting the input-SEL register to 2.
• IN5 (pins 19-23): Not used.
The output of the ICX2200 is three lines of video (RGB)
and two lines of sync (HV). The RGB lines are connected
to the video output board and the Sync (HV) lines are
connected to the input of ICX2600.
The video output board gets the RGB output from the
ICX2200 to drive the CRT. It also returns a signal (IK –
Cathode current) to pin 41 (IK-IN) of ICX2200. This is
used to control the correct black level of the three
amplifiers (AKB circuit).
ICX2600 is a deflection processor and compensation
circuit for multi-scan signals. This IC accepts the output
sync from ICX2200 and generates the signals needed
for the large signal deflection board. Since CS Chassis
sets use only two formats (NTSC using 15KHz at 60Hz,
and 37.9KHz at 60Hz), the IC uses point scan mode
and all other frequencies are set as invalid.
ICX2600 generates signals:
• Horizontal drive (H-DRV), East-West correction
(EW), and positive and negative Vertical ramps
(+VDRIVE, -VDRIVE) used in the horizontal and
vertical deflection circuit.
• Vertical Parabola (VPARAB) and Horizontal
Sawtooth (Hsaw) are both used in the dynamic
focus circuit.
• Two signals, F0 and FH_STATUS, use the
deflection circuit to switch the frequency of
the deflection circuit between 15KHz and
37.9KHz.
• The sandcastle pulse (SCP) and Vertical timing
pulse (VTIM) are fed back to the ICX2200. This
is used as a reference for the internal blanking
circuit and the AKB timing generator.
And accepts from the deflection circuit:
• The fly back pulse (H-FBP) is used for
synchronizing the deflection with the H-DRV
pulse generated in the IC.
• H-PROT signal is used in shutdown protection.
• V-PROT is used to protect the CRT.
• The ABL signal is used by the ICX2200 and
ICX2600 to regulate the size of the vertical
and horizontal size and the current of electronic
beam.
VIDEO PROCESSING
COMB FILTER
The function of the Glass Comb Filter is to separate the
composite video signal into Luminance (Y) and
Chrominance (C) signals with a minimum amount of Cross
Luminance and Cross Chrominance. The Glass Comb Filter
is a hybrid integrated circuit together with a glass delay
line combined into a five-pin package. The filter converts
the composite signal to an acoustic signal using a
piezoelectric transducer. The acoustic signal is sent
through the glass delay line where it is delayed by one
horizontal scan line. It is then converted back to an
electrical signal. This is called 1H delay, which
corresponds to one horizontal scan line time period.
Hence the name 1H COMB. This current undelayed line
is summed with the delayed line to give Y_COMB and
subtracted from the delayed line to give C_COMB. This
is made possible by the interleaving of Luminance and
Chrominance signals during one horizontal scan line.
The glass comb filter receives composite video from
ICX2900 pin 36 (Vout2) and separates it into Luma (Y)
and Chroma (C) signals. The Luma (Y) signal passes
through a 3.58MHz Trap in order to eliminate the
residual signal of Chrominance, and then is sent back
to pin 9 (YinS1) and pin 48 (Yin1) input with different
levels (because the levels of the signals are different to
RF and CV). The Chroma (C) signal goes to two different
3.58MHz Band Pass Filters decoupled by an emitter
follower (one for RF and the other for CV) in order to
eliminate the Luminance signal from the chroma signal
of each input. Then it is sent to pins 11 (CinS1) and
40 (Cin1) inputs of ICX2900.
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