Purity Adjustment - Sharp CX51N3 Service Manual

ADJUSTMENT PRECAUTION: Make sure TV Set in "Nomal Condition" before switch to Service Mode for Adjustment.
PIF ADJUSTMENT
NO. Adjustment part Adjusting procedure and conditions
1 Tuner IFT 1. Get the tuner ready to receive the E-9 CH
(PRESET) signal, but with no signal input.
Adjust the PLL data.
2. Connect the sweep generator's output cable
to the tuner antenna. (RF SWEEP)
3. Adjust the sweep generator's to 80dBuV.
4. Connect the response lead (use LOW IMPED-
ANCE probe with wave detector; see Fig.1) to
the tuner's IF output terminal. (This terminal
must have the probe alone connected).
5. Set the RF AGC to 0 - 6 V with no saturation
with the waveform.
6. Adjust the tuner IF coil to obtain the waveform
as shown in Fig. 2.
Note: Be sure to keep the tuner cover in
position during this adjustment.
2 RF-AGC 1. Receive "PAL COLOUR BAR" signal.
» Signal Strength: 57 ±1 dBµV (75 ohm open)
TAKE OVER
POINT
ADJUSTMENT 2. Connect the oscilloscope to TP201 (Tuner's
(I 2 C BUS AGC Terminal) as shown in Fig. 3.
CONTROL)
Oscilloscope
+
0.1V
–
Bias box
+
–
» Bias box: About 4.5 V
Fig. 3
3. Call "AGC" mode in service mode. Adjust the
"AGC" bus data to obtain the Tuner output pin
drop 0.1 V below maximum voltage.
4. Change the antenna input signal to
63~67dBµV, and make sure there is no noise.
5. Turn up the input signal to 90~95 dBµV to be
sure that there is no cross modulation beat.
Waveform and others
1n60
10k
Oscilloscope
100k 75ohm
Fig. 1
E-9 CH
P
Fig. 2
Note:
For the 50 ohm signal strength
gauge, when not using 50/75
impedance adapter, signal
± µ
strength is 52 1 dB V(75 ohm
±
open), instead of 57
(75 ohm open).
TP201
Precaution:
The loss of using impedance
adapter
TV Set
7-1
NO. Adjustment part
PURITY ADJ. 1. Receive the GREEN-ONLY signal. Adjust the
1
1000p
2. Degauss the CRT enough with the degausing
IF OUT
3. Maintain the purity magnet at the zero mag-
4. Observe the points a, b, as shown in Fig. 1-1
5. Orient the raster rotation to 0 eastward.
C
6. Tighten up the deflection coil screws.
-1.5+/-0.8dB
7. Make sure the CRT corners landing meet the
* For the following colours press R/C RGB key to
change.
µ
1 dB V

PURITY ADJUSTMENT

Adjusting procedure and conditions
beam current to ~ 700 µA
coil.
netic field and keep the static convergence
roughly adjusted.
through the microscope. Adjust the landings
to A rank requirement.
» Tightening torque: 108N ± 20 N
(11kgf ± 2 kgf)
A rank requirements. If not, stick the magnet
sheet to correct it.
Note:This adjustment must be done after
warming up the unit for 30 minutes or
µ
longer with a beam current over 700 A.
Green-only Blue-only Red-only
Signal-colour
screen cleared
7-2
Waveform and others
a
b
Fig. 1-1
A
B
A = B
Fig. 1-2
Rank "A"
(on the right of the CRT)
A
B
A = B
Fig. 1-3
Rank "A"
(on the left of the CRT)
* Press R/C RGB key for 1 sec-
ond in NORMAL MODE, the col-
our will change to RGB mono
colour mode.