Purity Adjustment - Sharp 14BM2 Service Manual

PIF ADJUSTMENT
NO. Adjustment part Adjusting procedure and conditions
1 TUNER IFT 1. Get the tuner ready to receive the E-9 CH sig-
(PRESET) nal, 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 80dBµV.
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 posi-
tion 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
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
1 PURITY 1. Receive the GREEN-ONLY signal. Adjust the
beam current to ~700 µA (21" & 20")/~500 µA
ADJUSTMENT
(14").
1000p
2. Degauss the CRT enough with the degausing
IF OUT
coil.
75ohm
Note: Follow the Job Instruction Sheet to ad-
C
3. Maintain the purity magnet at the zero mag-
-1.5+/-0.8dB
netic field and keep the static convergence
roughly adjusted.
4. Observe the points a, b as shown in Fig. 4-1
through the microscope. Adjust the landings
to the rank A requirements.
5. Orient the raster rotation to 0 eastward.
6. Tighten up the deflection coil screws.
» Tightening torque: 108 ± 20 N (11 ±2 kgf)
7. Make sure the CRT corners landing meet the
A rank requirements. If not, stick the magnet
sheet to correct it.
Note: This adjustment must be done after
± µ
1 dB V
Note: Set the service mode by JA122 &
* For the following colours press R/C RGB key
to change.
Green only

PURITY ADJUSTMENT

Adjusting procedure and conditions
just the magnetic field.
Vertical Bv : +0.030 mT
(0.30 gauss)
Horizontal Bh : +0.020 mT
(0.20 gauss)
(Reference: page 8/21)
warming up the unit for 30 minutes
or longer with a beam current over
µ
700 A. (21" & 20")
(For 14", the beam current should be
µ
over 500 A).
JA124 (short) then press factory proc-
ess R/C RGB key to change to RGB
mono colour mode.
Red only
Blue only
* Press R/C RGB key for 1 second
in NORMAL MODE, the colour
will change to RGB mono colour
Signal colour
mode.
screen cleared
Text Key "R.G.Cy"" Key can be
directly use to change to other
colours screen.
7-2
Waveform and others
a
b
Fig. 4-1
A
B
A = B
Fig. 4-2
Rank "A"
(on the right of the CRT)
A
B
A = B
Fig. 4-3
Rank "A"
(on the left of the CRT)