Sharp 21XF30, Service Manual

Page: 8 / 58

8
21XF30
21XF50
8-1
8-2
PIF ADJUSTMENT
No.
Adjusting point
Adjusting pr
ocedure/conditions
W
a
vef
orm and other
s
T
uner IFT
( PRESET )
1
1
.
Get the tuner ready to receiv
e the CH.
E - 9
signal,b
ut with no signal input.
Adjust the PLL data.
2
.
Connect the s
w
eep gener
ator's output cab
le to
the tuner antenna. ( RF SWEEP )
3.
Adjust the s
w
eep gener
ator's to 80dB
µ
V.
4.
Connect the response lead ( use LO
W IMPED-
ANCE probe with w
a
v
e detector ;
see Fig.1 ) to
the tuner's IF output ter
minal.
(
This ter
minal
m
ust ha
v
e
the probe alone connected ).
5
.
Set the RF A
GC to 0 - 6
V with no satur
ation with
the w
a
v
e
fo
rm
.
6
.
Adjust the tuner IF coil to obtain the w
a
v
ef
or
m as
sho
wn in Fig.
2.
Note:
B
e
sure to keep the tuner co
ver in posi-
tion during this adjustment.
RF-A
GC
T
AKE O
VER
POINT AD- JUSTMENT (I2C B
U
S
CONTR
OL)
1.
Receiv
e "P
AL COLOUR BAR" signal.
»
Signal Strength: 56
±
1 dB
µ
V (75 ohm open)
2
.
Connect the oscilloscope to
TP201 (T
uner’
s A
G
C
T
e
rminal) as sho
wn in Fig.
3.
3
.
Call "A
GC" mode in ser
vice mode
. Adjust the
"A
GC" b
us data to obtain the
T
uner output pin drop
0.1V belo
w maxim
um v
oltage
.
4.
Change the antenna input signal to 63~67dB
µ
V,
and mak
e sure there is no noise
.
5
.
T
u
rn
up the input signal to 90~95 dB
µ
V to be sure
that there is no cross modulation beat.
2
Fig. 3
Fig.1
Fig.2
Note: For the 50 ohm signal
strength gauge
, when not us-
ing 50/75 impedance adapter
,
signal strength is 54
±
1dB
µ
V(75 ohm open), in-
stead of 56
±
1dB
µ
V (75 ohm
open).
Precaution:
The loss of using
impedance adapter
.
E-9 CH
P
C
10k 100k
1n60
75ohm
IF OUT
-1.5+/-0.8dB
1000p
1000p
Oscilloscope
»
Bias box:
About 4.5 V
Oscilloscope
0.1V
TV Set
Bias box
TP201
+
+
—
—
SIF (NICAM/A2) ADJUSTMENT
No.
Adjusting point
Adjusting pr
ocedure/conditions
W
a
vef
orm and other
s
VCO COIL T2300
1
1.
Recie
v
e "P
AL colour bar" signal.(E-69)
(Set AFT ON 855.25MHz frequency).
2.
Connect DC
V
o
ltmeter to
TP202 (MAIN BO
ARD
TEST POINT).
3
.
Chec
k and tur
n
T2300 counter-cloc
kwise (Left)
to 0V and then tur
n it cloc
kwise (Right) until
TP202
become 5V
.
After that, tur
n
T2300 counter-cloc
kwise (Left) until
TP202 became 2.5
±
0.1Vdc.
*UNIT BO
ARD ADJUSTMENT
Vcc
5V
±
0.1V
IF Input F
requency
38.9MHz
±
0.1V
Adjust
T2300 unit
TP2300(NICAM/A2 BO
ARD
TEST POINT) become 2.5
±
1.0V
Chec
k after assemb
ly NICAM/A2 BO
ARD
T
est point:
TP202 (IN MAIN BO
ARD).
Preset selected reception frequency (AFT OFF) Chec
k V
oltage
2.5V
±
1.0Vdc.
Precaution:
The
Vcc,
f
o
and other factor
s are
considered in the unit boar
d of the
1.0V tolerance whic
h diff
er fr
om the
adjustment accurac
y.