Transmitter Adjustments - Icom IC-7400 Service Manual

5-3 TRANSMITTER ADJUSTMENTS

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