Pll Adjustment - Icom IC-725 Service Manual

6-2
PLL
ADJUSTMENT
ADJUSTMENT ADJUSTMENT
CONDITIONS
MEASUREMENT
VALUE
ADJUSTMENT
POINT
UNIT
LOCATION UNIT
ADJUST
REFERENCE
FREQUENCY
1
•
Displayed frequency:
14.10000
MHz
•
Mode
:
USB
•
Receiving
PLL
0
Terminate P4
to
ground
with
a 50
Q
resistor.
Connect
the
RF
voltmeter
to P4.
Pre-set to center.
PLL Cl 34
2
Maximum
level
(More
than -F3
dBm)
L38,
L39
3
Connect
the
frequency counter
to P4.
61.4400
MHz
L35
H
After adjustment,
remove
the resistor
from P4 and
re-plug P4.
DOS CLOCK
1
•
Displayed frequency:
14.10000
MHz
•
Mode
:
USB
• Receiving
DDS
Connect the
frequency counter
to
IC4
pin
1 1
or IC5
pin 11.
5.24288
MHz DDS
Cl
DOS LOOP
1
•
Displayed frequency:
14.12650
MHz
•
Mode
:
AM
• Receiving
PLL Connect
the
oscilloscope
to
R133
(rear panel
side).
1.0
V
DC
PLL L30
2 • Displayed frequency:
14.12649
MHz
Approx. 2.0
V
DC
Verify
1ST LO
LOCK
VOLTAGE
1
• Displayed frequency: 7.99999
MHz
•
Mode '
:
USB
• Receiving
PLL Connect
the
oscilloscope
to
R77.
(shielding
case
side)
6.5
V
DC
PLL C35
2 • Displayed frequency: 14.99999
MHz
6.5
V
DC C46
3
• Displayed frequency: 21 .99999
MHz
6.5
V
DC C59
H
• Displayed frequency: 33.00000
MHz
7.5
V
DC
C70
5
•
Displayed frequencies
0.50000
MHz,
8.00000
MHz,
15.00000
MHz
and 22.00000
MHz
More
than 2.0
V
DC
Verify
1STLO
OUTPUT
LEVEL
1
•
Displayed frequency:
14.10000
MHz
•
Mode
:
USB
• Receiving
PLL
Terminate P5
to
ground
with
a 50
O
resistor.
Connect
the
RF
voltmeter to P5.
More
than 0
dBm
Verify
2
After adjustment,
remove
the resistor
from P5 and
re-plug P5.
RIT
1
• Displayed frequency: 14.10000
MHz
•
Mode
:
USB
• Set the
signal
generator;
Level
:
50
pV (-73 dBm)
Modulation
:
OFF
• [RIT]
switch
:
ON
and
OFF
• Receiving
Top
cover
Speaker
Pre-set to center.
Front
panel
[RIT]
control
2
Same
tone pitch
on
both conditions.
PLL R70