Sharp 21HF2-SS, Service Manual

Page: 16 / 73

21HF2-SS
3 – 13
[2] ADJUSTMENT
1. PIF ADJUSTMENT
No. Adjustment point Adjustment condition/procedure Waveform or others
1 Tuner IFT
( PRESET ) 1. Get the tuner ready to receive the CH. E - 9 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 80dBV.
4. Connect the response lead ( use LOW IMPEDANCE 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 wave-
form.
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 TAKE
OVER POINT
ADJUSTMENT
(I2C BUS CON-
TROL)
(AUTO & MANUAL
ADJ)
1. Receive "PAL COLOUR BAR" signal.
•
Signal Strength: 56
±
1 dBV (75 ohm open)
2. Connect the oscilloscope to TP201 (Tuner’s AGC Terminal) as
shown in Fig. 3-1.
3. Call "V01" mode in service mode. Adjust the "V01" bus data to
obtain the Tuner output pin drop 0.1~1.0V below maximum
voltage.
4. Change the antenna input signal to 63~67dBV and make sure
there is no noise.
5. Turn up the input signal to 90~95 dBV to be sure that there is
no cross modulation beat.
* for Auto ADJ
1) Receive “PAL COLOUR BAR” signal.
signal strength: 56 1dBV(75 ohm open)
2) Go to service mode.
3) Go to service data V01, press R/C to
oper ate auto key (Hex C1) and confirm the
“OK” display on the screen.
4) If appear NG, increase data some step and
pls repeat step 2.
5) proceed step 4 & 5 in manual mode.
E -9 C H
P C
10k
100k
1n60
75ohm
IF OUT
-1.5+/-0.8dB
1000p
1000p
Os cillos cope
F ig.1
F ig.2
B ias box: About 4.5 V
Os cillos cope
0.1V
T V S et
B ias box
T P 201 +
+
-
-
F ig. 3-1