8
Electrical adjustments
29
L7.3A
8
Electrical adjustments
Notes :
Unless stated otherwise, the supply voltage used is :
–
220v to 240v +/- 10%, 50 - 60 Hz +/- 5%.
–
Voltage and oscillograms are measured in relation to earth.
–
Never use a heatsink as earth.
For the adjustments a colour pattern generator PM5418 has
been used. Pattern generator type PM5193 (optional) .
8.1
Settings on the carrier panel
8.1.1
+ 140 V supply voltage for 25" and 29" picture tubes.
Connect a multimeter (DC) across C2551. Set brightness at
mid position and contrast at maximum. Apply a pattern
generator with a colour bar. Adjust potentiometer R3572 to 140
Volts +/- 1 V DC.
8.1.2
Geometry adjustments (software adjustment)
Set pattern generator (e.g. PM5418) with colour bar pattern
and connect to aerial input with RF signal amplitude - 1mv.
Enter SAM mode byusing the Dealer Service Tool or short-
circuit service pins M28 and M29 on PCB and switch power
"ON". The menu is displayed whenever SAM mode is entered.
Enter into GEOMETRY menu.
•
Vertical Amplitude and position
–
Select item VSH and set vertical shift to 31 (Nominal
value !!).
–
Select item VAM and align the top of the screen with
vertical amplitude.
–
Select item VSL and align the bottom of the screen
with vertical slope.
•
Horizontal Amplitude and phase
–
Select item HSH and align horizontal shift until picture
to center of the screen.
–
Select item EW and align the picture width (only those
sets with East-West drive circuit).
–
Select item PW and align East-West parabola for
straight vertical lines.
–
Select item TC and align east-west trapezium for a
rectangle.
–
Repeat if necessary.
General :
The value can be increment or decrement by pressing the user
remote control right or left key. The results of the picture will
change according to the selected item.
8.1.3
Focusing
Set pattern generator (e.g. PM5418) with colour bar pattern
and connect to aerial input with RF signal amplitude of 1mv.
Set brightness and contrast at maximum. Adjusted with
focusing potentiometer (upper hole of LOT 5445 ) for maximum
sharpness of the picture.
8.1.4
IF-PLL / RF AGC adjustment (software adjustment)
Set generator (e.g. PM5418) with colour bar pattern and set
frequency for PAL to 189.25MHz and for NTSC 55.25MHz with
RF signal amplitudeof 3mv (70dBuv) and connect this signal to
the aerial input.
Enter SAM mode by Dealer Service Tool or short-circuit service
pins M28 and M29 on PCB and switch power ON. The menu is
displayed whenever SAM mode is entered. Enter into TUNER
menu, select items IF-PLL for AFT alignment
Method Of Alignment
–
Set AFW to 80 kHz
–
Adjust IF-PLL until AFA & AFB just switching from "0" to
"1". The correct value for IF-PLL is 61.
Enter into TUNER menu, select items AGC for RF AGC
alignment.
Method Of Alignment
–
Connect a multimeter (DC) at pin 1 of tuner.
–
Adjust the AGC until the voltage at pin 1 of the tuner is
/- 0.4V DC. The correct value for AGC should be
37.
The value can be increment or decrement by pressing the user
remote control right or left key.
8.1.5
Picture demodulator adjustment
Connect a pattern generator (e.g. PM5418) with a cross hatch.
Connect an oscilloscope (1ms/div) to pin 6 of IC 7225-5A and
adjust L5260 so that the overshoot response is minimum .
Select a colour bar signal and verify if the picture is OK.
8.1.6
34.4MHz Trap Alignment
NOTE: For Pal multi set only.
GENERAL SET-UP
Connect Frequency Synthesizer PM5193 with sine wave and
signal strength of 100mv rms. (100dBuv) via a 50 ohm cable
terminated with a RC network(50ohm,10nF) and connect to
tuner C-CUT (C-CUT OPEN) . Output detection points at saw
filter coil 5040 ,pin 3of 1050. The capacitor is in series with the
signal, the resitor is vonnected to ground. Adjust L5040 for
minimum amplitude.
8.2
VG2 and White-D settings
8.2.1
Vg2 cut off alignment
Connect a pattern generator (e.g. PM5418) with a black picture
, set picture controls of the TV set as following :
Brightness: 25
Colour : 30
Contrast: 50
Switch on the TV set and measure with a 100 : 1 scope probe
at the cathodes of the picture tube socket pin 6,8 and 11 of
CRT sockets C83/84 ; alternately pin 6 for Green, pin 8 for Red
and pin 11 for Blue .
Measure the level of the pluses and adjust the level of the
highest pluses by means of the Vg2 potentiometer (lower knob
of LOT 5445). The DC level must be 140 Volts +/- 2V DC for
25" tubes and 16/-2V DC for 29" picture tubes.
