Icom IC-756PRO III - Transmitter Adjustments

4 - 4
4-3 TRANSMITTER ADJUSTMENTS
ADJUSTMENT ADJUSTMENT CONDITION
MEASUREMENT
VALUE
ADJUSTMENT
POINT
UNIT LOCATION UNIT ADJUST
IDLING
CURRENT
• Connect an RF power meter to [ANT1] connector.
• Turn R14, R16, R65 and R67 on the PA unit to max. CCW.
• Disconnect W16 from EP4, and connect an ammeter between W16(+) and EP4(–).
(for drive ampli-
fi er) 1
• Display freq. : 14.100000 MHz
• Mode : CW (Key up)
• [RF POWER] : Max. CW
• [TUNER] : OFF
• Transmitting (without key)
PA
Connect an ammeter
between W16(+) and
EP4(–).
Measure the cur-
rent, and memorize
it as the reference.
PA
–
2
1 A more than
reference
R14
3
2 A more than
reference
R16
(for fi nal
amplifi er) 1
• Display freq. : 14.100000 MHz
• Mode : CW (Key up)
• [RF POWER] : Max. CW
• [TUNER] : OFF
• Transmitting (without key)
PA
Connect an ammeter
between W16(+) and
EP4(–).
Measure the cur-
rent, and memorize
it as the reference.
PA
–
2
1 A more than
reference
R65
3
2 A more than
reference
R67
• After the IDLING CURRENT adjustment, connect the W16 and EP4.
TX PEAK
1
• Display freq. : 14.100000 MHz
• Mode : USB
• Set following selections, controls
and functions as :
[VOX] : OFF , [ TX] : OFF
PBT1 : Center , PBT2 : Center
Filter : 2.4 kHz
[RF POWER] : Max. CW
[MIC GAIN] : Center
[TUNER] : OFF
[METER] : METER Po
[MONITOR] : OFF
• Apply no audio signals to [MIC]
connector.
• Transmitting
MAIN-A
Connect a digital mul-
timeter or oscilloscope
to the check point
CP243.
0.06 V MAIN-A R247
2
• Connect an audio generator to
[MIC] connector and set as:
Frequency : 1.5 kHz
Level : 1 mVrms
• Transmitting
Rear
panel
Connect an RF power
meter to [ANT1] con-
nector.
50 W
Front
panel
[MIC GAIN]
control
3 • Transmitting
Maximum output
power
MAIN-A L261
4
• [MIC GAIN] : Center
• 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 : 10 mVrms
• Transmitting
RF-B
Connect an RF volt-
meter the check point
J201.
Maximum level RF-B
L1801,
L1553,
L1702,
L1701
Adjust in sequence L1801, L1553, L1702, L1701, L1702, L1701
TRANSMITTER
TOTAL GAIN
1
• Display 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
Rear
panel
Connect an RF power
meter to [ANT1] con-
nector.
50 W MAIN-A R263