Transmitter Adjustments - Icom IC-756PROIII Service Manual

4-3 TRANSMITTER ADJUSTMENTS

ADJUSTMENT ADJUSTMENT CONDITION
IDLING 1 • Display freq.
CURRENT
• Mode
(for drive)
• Preset R11, R18 on the PA unit to
max. CCW
• [RF POWER]
• [TUNER]
• Transmitting (without key)
After adjustment, re-solder the wire (W29) on the PA board
(for fi nal 2 • Transmitting (without key)
amplifi er)
After adjustment, re-solder the wire (W29) on the PA board
TX PEAK 1 • Display freq.
• Mode
• Set following selections, controls
and functions as :
[VOX] : OFF
PBT1 : Center , PBT2 : Center
Filter
[RF POWER] : Max. CW
[MIC GAIN] : Center
[TUNER]
[METER]
[MONITOR] : OFF
• Apply no audio signals to [MIC]
connector.
• Transmitting
2 • Connect an audio generator to
[MIC] connector and set as:
Frequency
Level
• Transmitting
3 • Transmitting
4 • [MIC GAIN]
• Preset L1701, L1702's top to same
high with coil's case.
• Connect an audio generator to
[MIC] connector and set as:
Frequency : 1.5 kHz
Level
• Transmitting
Adjust in sequence L1801, L1553, L1702, L1701, L1702, L1701
TRANSMITTER 1 • Display freq.
TOTAL GAIN • Mode
• [MIC GAIN]
• Connect an audio generator to
[MIC] connector and set as:
Frequency : 1.5 kHz
Level
• Transmitting
UNIT
PA
: 14.100000 MHz
: CW (Key up)
: Max. CW
: OFF
PA
: 14.100000 MHz MAIN-A C o n n e c t a d i g i t a l
: USB
, [ TX] : OFF
: 2.4 kHz
: OFF
: METER Po
Rear
panel
: 1.5 kHz
: 1 mVrms
: Center RF-B
: 10 mVrms
: 14.100000 MHz Rear
: USB panel
: Center
: 1 mVrms
4 - 4
MEASUREMENT
LOCATION
Unsolder W29.
Connect an ammeter to
the unsoldering points
of W29.
U n s o l d e r R 2 8 ( L 8
side).
Connect an ammeter to
the unsoldering points
of R28.
multimeter or oscil-
loscope to the check
point CP243.
Connect an RF power
meter to [ANT1] con-
nector.
Maximum output
power
Connect an RF volt-
meter the check point
J201.
Connect an RF power
meter to [ANT1] con-
nector.
ADJUSTMENT
POINT
VALUE
UNIT
250 mA PA
500 mA PA
0.06 V MAIN-A
50 W Front
panel
MAIN-A
Maximum level RF-B
50 W MAIN-A
ADJUST
R11
R18
R247
[MIC GAIN]
control
L261
L1801,
L1553,
L1702,
L1701
R263