Selects a desired radio wave and changes it to the video IF signal.
2 — Video IF Amp.: Q200 2SC4238
Amplifies the video IF signal output from the tuner TU by 10 times (20 dB).
3 — Video Det./Sound Det./FM Det./AFT/AGC: IC200 M51348FP
Eliminates the carrier wave in the video IF signal, and picks up the video signal and the sound IF signal.
Also, the sound signal is picked up from the sound IF signal by FM detection.
4 — Audio Amp.: IC600 NJM2070M
Sound amplification.
Segment
Driver
5 — Chroma Circuit: IC300 M52042FP
Generates the tricolor (red, green, and blue) from the video signal.
Converts the color signal into a digital signal.
Also, generates the clock pulse for the display and controls the display.
7 — Tuning Voltage Generator: IC500 MSC1169MS-K
Generates the tuning voltage with the tuning pulse (TU) output from 6.
8 — Display Voltage Generator: Q800~Q802, Q804~Q806, 2SD601A-R x 4, 2SB709A-R, 2SD1149-S
Generates the display voltages V0 ~ V4 with VEE1 and VCC7 outputs from the power supply.
— 2 —
CIRCUIT DESCRIPTION
TUNING VOLTAGE GENERATOR
BT
BS
16
15
BS
Vcc
VCC6
IC500 MSC1169MS-K
14
BT
13
IN
12
OUT
11
TU
10
H/L
TU
H/L
BU
9
U/V
VREFU1U2
1
2
VL1
VL2
VH1
VH2
GND
3
4
5
6
7
8
VREF
R500R501R502
GND
Figure 1
This circuit generates the DC tuning voltage BT for selecting a channel with a TU pulse being output from
IC700.
IC500 has 3 circuits for converting pulses to voltages; it selects one of VHF-L, VHF-H, or UHF, and
causes the tuning voltage to be output from the OUT terminal (pin 12). Figure 2 and Table 1 show the
conditions for selection.
IC500
TU
11
VHF
-L
VHF
-H
UHF
910
U/V H/L
Figure 2
12
OUT(BT)
— 3 —
Inputs
U/V
L
L
H
H
H/L
L
VHF-L receiving
H
VHF-H receiving
L
UHF receiving
H
UHF receiving
Table 1
Function
POWER SUPPLY
Vref
VCC1-1
C100
D100
C105
CP100
VR100
R101
C135
Q100
Q101
R111
R102
C140
Q111
R115
C145
R117
Figure 3
1
9
CP104
T100
GND
VCC2-2
L102
D155
32
4
5
D152
6
7
D150
D152
C112
L101
C110
C113
VCC2-3
R133
VCC7
CP108
VCC6
CP107
VCC2
CP109
VEE1
CP110
C115
C114
The power supply consists of a DC-DC converter and causes the voltages to be output as shown in Table 2.
NameVoltageFunction
VCC23.95 ± 0.02 VMain voltage
VCC630.5 ~ 39.0 VTuning voltage
VCC753.5 ~ 72.5 VTuning voltage/Display voltage
VEE1–6.3 ~ –7.9 VDisplay voltage
Table 2
— 4 —
ADJUSTMENT
LINEAR PCB
Items To Be Adjusted
ItemMeasuring Instrument
VCC2 voltage settingVoltmeter
Video detection coil adjustmentTV signal generator, pattern generator, oscilloscope,
low-pass filter
AFT coil adjustmentSweep generator, oscilloscope, voltmeter
Contrast adjustmentTV signal generator, pattern generator, oscilloscope
AGC adjustmentTV signal generator, pattern generator, IF levelmeter