Sharp SX51LF7, Руководство по обслуживанию

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8
SX51LF7
SX51LF8
8-1
8-2
PIF ADJUSTMENT
No.
Adjusting point
Adjusting procedure/conditions
W
aveform and others
T
uner 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 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.
RF-AGC T
AKE OVER
POINT AD- JUSTMENT (I2C BUS CONTROL)
1.
Receive "P
AL
COLOUR BAR" signal.
»
Signal Strength: 54 ± 1 dBµV (75 ohm open)
2.
Connect the oscilloscope to
TP201 (T
uner
’s
AGC
T
erminal) as shown in Fig. 3.
3
.
Call "AGC" mode in service mode.
Adjust the
"AGC" bus data to obtain the
T
uner 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.
T
urn 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 54±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
1000p
Oscilloscope
Fig.1
Fig.2
SIF (NICAM/IGR)
ADJUSTMENT
No.
Adjusting point
Adjusting procedure/conditions
W
aveform and others
VCO COIL T2300
1
1.
Receive “P
AL
colour bar” signal.(E-69)
(Set
AFT
ON 855.25MHz frequency).
2.
Connect DC V
oltmater to
TP202 (MAIN BOARD
TEST POINT).
3.
Check and turn
T2300 counter-clockwise (Left)
to 0V and then turn it clockwise (Right) until
TP202
become 5V
.
After that, turn
T2300 counter-clockwise (Left) until
TP202 became 2.5 ± 0.1Vdc.
*
UNIT
BOARD
ADJUSTMENT
Vcc
5V ± 0.1V
IF Input Frequency
38.9MHz ± 0.1V
Adjust
T2300 unit
TP2300 (NICAM BOARD
TEST
POINT) become 2.5 ± 1.0V Check after assembly NICAM BOARD T
est point:
TP202 (IN MAIN BORD).
Preset selected receptiion frequency (AFT OFF) Check V
oltage 2.5 ±
1.0Vdc.
Precaution: The Vcc, fo and other factors are
considered in theunit board of the 1.0V tolerance which differ from the adjustment accuracy
.