Service manual

11
14GT15
14GT20
PIF ADJUSTMENT
No. Adjusting point Adjusting procedure/conditions Waveform and others
Tuner IFT
( PRESET )
1 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 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.
RF-AGC
TAKE OVER
POINT AD-
JUSTMENT
(I
2
C BUS
CONTROL)
1. Receive "PAL COLOUR BAR" signal.
» Signal Strength: 57 ± 1 dBµV (75 ohm open)
2. Connect the oscilloscope to TP201 (Tuner’s AGC
Terminal) as shown in Fig. 3.
3. Call "AGC" mode in service mode. Adjust the
"AGC" bus data to obtain the Tuner output pin
drop 0.1V 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.
Note: For the 50 ohm signal
strength gauge, when not
using 50/75 impedance
adapter, signal strength is
52±1dBµV(75 ohm open), in-
stead of 57±1dBµV (75 ohm
open).
Precaution: The loss of using
impedance adapter
2
» Bias box: About 4.5 V
Oscilloscope
0.1V
TV Set
Bias box
TP201+
+
–
–
Fig. 3
E-9 CH
P C
10k
100k
1n60
75ohm
IF OUT
-1.5+/-0.8dB
1000p
Oscilloscope
Fig.1
Fig.2