Table of Contents
Advertisement
Y Safety Precautions
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.
But this is changeable in view of productivity.
5. Unless otherwise noted, set the line voltage to
230Vac!10%, 50Hz.
Y Test Equipment required
1. RF signal generator (with pattern generator) 1[EA]
2. DC Power Supply
3. Digital Multimeter (volt meter) 2[EA]
4. Oscilloscope 2[EA]
5. White balance meter 1[EA]
: VCO (Voltage Controlled Oscillator) Adjustment
Test Point
: J72
Adjust
: L107
Ceramic
CAP.
38.9MHz
10000pF
RF
Signal
generator
3
Ceramic
CAP.
10000pF
GND
L106
5Vdc
Power
Supply
GND
Fig.1 : Connection Diagram of Equipment for VCO Adjustment.
1) Turn on DC power supplies.
2) Adjust Video Detector Coil (L107) for 2.85! 0.1Vdc.
NOTE : The condition of signal Generator.
Frequency
38.9MHz
: RF AGC (Auto Gain Control) Adjustment
ADJUSTMENT
IC102
TDA9815
4
5
L107
Z101
(VCO ADJ.)
G3962
J72
IC01
u-COM
C115(-)
L01
Modulation
Output level
OFF
80dBu
Test Point
Adjust
The RF AGC control (VR101) was aligned at the time of
manufacture for optimum performance over a wide range
conditions. Readjust of VR101 should not be necessary
unless unusual local conditions exists, such as:
Digital
Multimeter
Fig. 2 : Connection Diagram of Equipment for AGC Adjustment.
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.
Multimeter &
3) Picture noise caused by "broadcast noise" or weak signal.
oscilloscope
If the broadcast is "clean" and the RF signal is at least
2.85Vdc
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 jother end of rotation will usually cause a
degradation of over load capabilities resulting in color beats or
adjacent channel reference.
Adjustment (Refer to Table 1)
VL (Vertical Linearity)
Adjust so that the boundary line between upper and lower
half is in accord with vertical blanking line.
VS (Vertical Shift)
Adjust so that the horizontal center line of digital circle
pattern is in accord with geometric horizontal center of
the picture tube.
VH (Vertical Height)
Adjust inside of the circle at top and bottom display.
- 1 -
: J189 or Observing Display
: VR101
AGC TP.
J189
Tuner
VR101
(AGC ADJ.)
IF Board
Advertisement
Table of Contents
