Pll Adjustment - Icom IC-726 Service Manual

6-2
PLL
ADJUSTMENT
ADJUSTMENT
DDS CLOCK
1
REFERENCE
FREQUENCY
2
3
DDS LOOP
1
HF
1st
LO
LOCK
VOLTAGE
1
2
3
5
50
MHz
1st
LO
OUTPUT
LEVEL
1
2
3
ADJUSTMENT CONDITIONS
MEASUREMENT
VALUE
ADJUSTMENT
POINT
UNIT
ADJUST
UNIT
LOCATION
•
Displayed frequency: 14.10000
MHz
•
Mode
:
USB
• Receiving
DDS
Connect
the
frequency counter
to IC4, pin 11 or IC5,
pin 11.
5.24288
MHz
DDS
Cl
•
Displayed frequency:
14.10000
MHz
•
Mode
:
USB
•
Ground P4
with a
50
Q
resistor.
• Receiving
PLL
Connect
the
RF
voltmeter to P4.
Preset
to
center as
shown
below.
PLL Cl 34
Maximum
level
(More than -F3
dBm)
L38, L39
Connect
the
frequency counter
to P4.
61.4400
MHz
L35
After adjustment,
remove the
resistor
from
P4 and
re-plug P4.
-
—
1
•
Displayed frequency:
14.12650
MHz
•
Mode
:
AM
• Receiving
PLL Connect
the
oscilloscope to
R
133
(rear
panel
side).
1.0
V
DC PLL L30
•
Displayed frequency:
14.12649
MHz
Approx. 2.0
V
DC
Verify
After adjustment,
fix
the
L30
in
place with
paraffin.
• Displayed frequency:
7.99999
MHz
•
Mode
:
USB
•
Receiving
PLL Connect
the
oscilloscope
to
R77
(shielding
case
side).
6.5
V
DC PLL
C35
• Displayed frequency:
14.99999
MHz
6.5
V
DC C46
• Displayed frequency: 21
.99999
MHz
6.5
V
DC C59
• Displayed frequency:
33.00000
MHz
7.5
V
DC C70
•
Displayed frequencies:
0.50000
MHz,
8.00000
MHz
15.00000
MHz
and 22.00000
MHz
More
than 2.0
V
DC
Verify
• Displayed frequency:
53.00000
MHz
•
Mode
:
USB
•
Terminate P5
with a 50
Q
resistor.
•
Receiving
PLL Connect
the
RF
voltmeter to P5.
Maximum
level
(More than
-F3
dBm)
PLL
Adjust
in
sequence
L52, L53,
L54, L58,
L59, L60,
L61
• Shift the
frequency
between
50.00000
MHz
and 54.00000 MHz.
Adjust the output
level
within -F2
dBm.
Adjust
in
sequence
L58, L59,
L60, L61
After adjustment,
remove the
resistor
from
P5 and
re-plug P5.
6
—
2