Transmitter Adjustment - Icom ic-775 Service Manual

5-4
TRANSMITTER
ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITIONS
MEASUREMENT
VALUE
ADJUSTMENT
POINT
UNIT
LOCATION
UNIT
ADJUST
IDLING
CURRENT
1
• Displayed frequency
:
1
4.1
00000
MHz
.
Mode
:
USB
•
[PWR]
control
:
Maximum
•
[MIC] control
:
Minimum
•
R9 (PA
unit)
:
Max.
counterclockwise
•
R18 (PA
unit)
:
Max.
counterclockwise
•
R21 (PA
unit)
:
Max.
counterclockwise
• Transmitting
PA
Connect a
DC
ammeter
between the connector
(W5;
one
of red wires)
and
REG
unit.
Connect a
jumper wire
between
black cables.
1
00-200
mA DC
ammeter
Verify
(for
drive
amplifiers)
2
150
mA
increase
from step
1
PA R9
(for final
amplifiers)
3 50
mA
increase
from step
2
R18
4
250
mA
increase
from
step
3
R21
5
200
mA
increase
from step
4
R18
CARRIER
SUPPRESSION
1
• Displayed frequency:
14.100000
MHz
•
Mode
:
USB
and LSB
•
[ANT]
;
1
• Apply
no
signal
to
[MIC] connector.
• Transmitting
Rear
panel
Connect a spectrum
analyzer
to
[ANTI].
Minimum
level IF
R273,
R274
TRANSMIT
LEVEL
•
Displayed frequency
:
1
4.1
00000
MHz
.
Mode
:
RTTY
•
[DRIVE]
:
Max.
clockwise
•
[PWR]
control
:
Max. clockwise
•
R80 (RF
unit)
:
Center
• Transmitting
RF
Terminate J8
to
ground
with
a 50
O
resistor.
Connect an
RF
voltmeter
to J8.
Maximum
output
RF
Adjust
in
sequence
L57,
L161,
L60, L58
MIXER
BALANCE
1
•
Displayed frequency
:
24.900000
MHz
and
14.100000
MHz
•
Mode
FM
•
[ANT]
:
1
• Transmitting
Rear
panel
Connect a spectrum
analyzer
to
[ANTI]
via
an
attenuator.
Minimum
adja-
cent spurious
level
on
the both
frequencies
RF R80
TRANSMIT
TOTAL
GAIN
1
• Displayed frequency
:
14.100000
MHz
.
Mode
:
USB
•
[MIC] control
Center
.
[COMP]
:
OFF
•
[MIC
TONE]
:
Center
.
[ANT]
:
1
•
Connect an audio generator
to
[MIC]
connector and
set as:
Frequency
:
1
.5
kHz
Level
:
3
mV
• Transmitting
Rear
panel
Connect an
RF
power
meter
to
[ANTI].
Maximum
output
level
IF Adjust
in
sequence
LI
8,
L7.
L39,
L8
2
100
W
R23
OUTPUT
POWER
1
•
Displayed frequency
:
14.1
00000
MHz
•
Mode
:
USB
•
[ANT]
:
1
•
Connect an
audio generator
to
[MIC]
connector
and
set as:
Level
:
30
mV
• Transmitting
Rear
panel
Connect an
RF
power
meter
to
[ANTI].
200
W
IF
R364
2
•
Mode
AM
•
MIC
gain [MIC]
:
Minimum
• Apply
no
signal to [MIC] connector.
55
W
R362
COMP
AMPLIFIER
1
•
Displayed frequency
:
14.100000
MHz
.
Mode
:
USB
.
[COMP]
:
ON
•
[DRIVE]
:
Max. clockwise
.
[ANT]
:
1
•
Connect an
audio generator
to
[MIC]
connector
and
set as:
Level
:
3
mV
•
Transmitting
Rear
panel
Connect an
RF
p>ower
meter
to
[ANTI].
SOW
Front
panel
MIC
gain
control
[MIC]
2
Maximum
output
level
Lie.
L17
5-8