Icom IC-7400, Service Manual, Page: 20 / 92

5-3 TRANSMITTER ADJUSTMENTS
IDLING
CURRENT
(for driver)
(for HF/50 M
band final
amplifier)
(for 144 M
band final
amplifier)
144 M PEAK
TX PEAK
TRANSMITTER
TOTAL GAIN
Ic APC
1
2
3
1
1
2
3
1
1
• Displayed freq. : 14.100000 MHz
• Mode
: USB
• [MIC GAIN] : Max.CCW
• [RF POWER] : Max. CW
• [TUNER] : OFF
• Preset R11, R18, R204 (PA unit) to
max. counter clockwise.
• Turn C202 (PA unit) to 90˚ clock-
wise.
• Transmitting
• Transmitting
• Displayed freq. : 144.00000 MHz
• Mode
: USB
• Transmitting
• Displayed freq. :
146.00000 MHz [USA]
144.00000 MHz [except USA]
• Mode : RTTY
• Transmitting
• Displayed freq. : 145.00000 MHz
• Mode
: USB
• Set following controls as:
[RF POWER] : Max. CW
[MIC GAIN]
: Center
[KEY SPEED] : Center
[PITCH]
: Center
• Disconnect P1 (PA unit) from J151
(RF unit).
• Connect an audio generator to
[MIC] connector and set as:
Frequency : 1.5 kHz
Level : 1 mVrms
• Transmitting
• Displayed freq. : 14.100000 MHz
• Mode
: USB
• Connect an audio generator as:
Frequency : 1.5 kHz
Level : 1 mVrms
• Transmitting
• Transmitting
• Displayed freq. : 14.100000 MHz
• Mode
: USB
• [MIC GAIN] : Center
• Connect an audio generator to
[MIC] connector and set as:
Frequency : 1.5 kHz
Level : 1 mVrms
• Transmitting
• Mode : RTTY
• Connect CP300 to GND.
• Transmitting on the maximum TX
current band.
PA
Rear
panel
RF
Rear
panel
Rear
panel
Rear
panel
Connect an ammeter
between the power
supply and the IC-
746PRO/7400.
Connect an RF
power meter to the
[ANT 144MHz] con-
nector.
Connect a digital
multimeter or oscillo-
scope to the check
point J151.
Connect an RF
power meter to the
[ANT1] connector.
Connect an RF
power meter to
[ANT1] connector.
Connect an ammeter
between power sup-
ply and the IC-
746PRO/7400.
+2.5 A
+300 mA
+1 A
Maximum output
power
Maximum output
Level
50 W
Maximum output
power
50 W
23 A
PA
PA
RF
Front
panel
MAIN
MAIN
MAIN
R11
R18
R204
C202
Adjust in
s e q u e n c e
L253, L252,
L251, L272
several times.
[MIC GAIN]
control
L330
R331
R555
5 - 4
ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITION
MEASUREMENT
VALUE
POINT
UNIT LOCATION UNIT ADJUST
After adjustment, re-connect P1 (PA unit) to J151 (RF unit).
After adjustment, disconnect the ammeter between the power supply and the IC-746PRO/7400.