Transmitter Adjustments - Icom IC-756proIII Service Manual

4-3 TRANSMITTER ADJUSTMENTS

ADJUSTMENT ADJUSTMENT CONDITION
IDLING • Connect an RF power meter to [ANT1] connector.
CURRENT • 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-
• Display freq.
fi er) 1
• Mode
• [RF POWER]
• [TUNER]
2
• Transmitting (without key)
3
(for fi nal
• Display freq.
amplifi er) 1
• Mode
• [RF POWER]
• [TUNER]
2
• Transmitting (without key)
3
• After the IDLING CURRENT adjustment, connect the W16 and EP4.
TX PEAK • Display freq.
• Mode
• Set following selections, controls
and functions as :
[VOX] : OFF
PBT1 : Center , PBT2 : Center
Filter
1 [RF POWER] : Max. CW
[MIC GAIN] : Center
[TUNER]
[METER]
[MONITOR] : OFF
• Apply no audio signals to [MIC]
connector.
• Transmitting
• Connect an audio generator to
[MIC] connector and set as:
2 Frequency
Level
• Transmitting
3 • Transmitting
• [MIC GAIN]
• Preset L1701, L1702's top to same
high with coil's case.
• Connect an audio generator to
[MIC] connector and set as:
4
Frequency : 1.5 kHz
Level
• Transmitting
Adjust in sequence L1801, L1553, L1702, L1701, L1702, L1701
TRANSMITTER • Display freq.
TOTAL GAIN • Mode
• [MIC GAIN]
• Connect an audio generator to
1
[MIC] connector and set as:
Frequency : 1.5 kHz
Level
• Transmitting
UNIT
: 14.100000 MHz
: CW (Key up)
: Max. CW
PA
: OFF
: 14.100000 MHz
: CW (Key up)
: Max. CW
PA
: OFF
: 14.100000 MHz
: USB
, [ TX] : OFF
: 2.4 kHz
MAIN-A
: OFF
: METER Po
: 1.5 kHz
Rear
: 1 mVrms
panel
: Center
RF-B
: 10 mVrms
: 14.100000 MHz
: USB
: Center
Rear
panel
: 1 mVrms
4 - 4
MEASUREMENT
LOCATION
rent, and memorize
Connect an ammeter
between W16(+) and
EP4(–).
rent, and memorize
Connect an ammeter
between W16(+) and
EP4(–).
Connect a digital mul-
timeter or oscilloscope
t o t h e c h e c k p o i n t
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
Measure the cur-
it as the reference.
1 A more than PA
reference
2 A more than
reference
Measure the cur-
it as the reference.
1 A more than PA
reference
2 A more than
reference
0.06 V MAIN-A
Front
50 W
panel
MAIN-A
Maximum level RF-B
50 W MAIN-A
ADJUST
–
R14
R16
–
R65
R67
R247
[MIC GAIN]
control
L261
L1801,
L1553,
L1702,
L1701
R263