Goldstar MC-993A Adjustment Instructions Manual

Safety Precautions
V
1. It is safe to adjust after using insulating transformer between
the power supply line and chassis input to prevent the risk of
electric shock and protect the instrument.
2. Never disconnect leads while the TV receiver is on.
3. Don't short any portion of circuits while power is on.
4. The adjustment must be done by the correct appliances.
5. Unless otherwise noted, set the line voltage to 230Vac!10%,
50Hz.
Test Equipment required
V
1. RF signal generator (with pattern generator)
2. DC Power Supply
3. Multimeter (volt meter)
4. Oscilloscope
5. Color analyzer
Main Board(Component side view)
V Multimeter or Oscilloscope
JP7 IC05
Power-
Supply
TP1
IC102
5V JP4
5V
L107
4.7kΩ
S3
JP5 VR102
Q106
S2
100Ω
Fig. 1 : Connection Diagram of Equipment for PIF Adjustment
O
PIF (Picture Intermediate Frequency) Adjustment
Test Point : TP1
Adjust : L107
1) Connect the measuring equipment to the Main Board as
shown in Fig.1.
2) Set RF frequency and output level of RF SIGNAL
GENERATOR as shown Table 1.
3) Turn off S1 and S3 and on S2.
4) Adjust L107 so that the DC voltage may be 2.5!0.1Vdc.
System Frequency
B/G,D/K/I,SECAM-L 38.9MHz
SECAM-L' 34.25MHz
ADJUSTMENT INSTRUCTIONS
1
IC101
TDA4474
Signal-
24
0.01pF
Generator
7 JP1
38.9MHz
JP2 34.25MHz
11
16
VR102
15
JP3
100Ω
S1
Modulation Output level
OFF 10mVp-p
OFF 10mVp-p
(Table 1)
O
SECAM-L' Adjustment
NOTE : This adjustment should be performed after PIF
adjustment.
Test Point
Adjust
1) Turn on S1 and S3 and off S2.
2) Adjust VR102 so that the DC voltage may be indicated
2.5!0.1Vdc.
O
RF AGC (Automatic Gain Control) Adjustment
Test Point
Adjust
The RF AGC control (VR101) was aligned at the time of
manufacture for optimum performance over a wide range
conditions. Readjustment of VR101 should not be necessary
unless unusual local conditions exist, such as ;
(B/G,D/K,I,L)
(SECAM-L') 1) Channel interference in a CATV system.
2) Picture bending and/or color beats, which are unusually due
to excessive RF signal input when the receiver is too close
to a transmitting tower or when the receiver is connected to
an antenna distribution system where the RF signal has
been amplified. In this case, the input signal should be
attenuated (with pad or filter) to a satisfactory level.
3) Picture noise caused by "broadcast noise" or weak signal.
If the broadcast is "clean" and the RF signal is at least 1mV
(60dBu), the picture will be noise free in any area.
Adjusting the VR101(RF AGC) control to one end of rotation
will usually cause a relatively poor signal to noise ratio;
Adjusting to the other end of rotation will usually cause a
degradation of over load capabilities resulting in color beats or
adjacent channel interference. For best results, adjust the
VR101 control while performing on all over local channels, or
the voltage at TP2 will be 2.3!0.1Vdc in RF level 65!1dBuV.
Adjust
L107
VR102
- 1 -
: TP1
: VR102
: J209 or Observing Display
: VR101