Icom Ic-2800 Dual Band Fm Tranciever Service Manual

4 - 5
4-3-3 UHF LOOP
The generated signal at the U-VCO (Q20, Q21, D20, D21)
enters the PLL IC (IC2, pin 15) via buffer-amplifiers (Q22,
Q23) and is divided at the programmable divider section and
is then applied to the phase detector section.
The phase detector compares the input signal with a refer-
ence frequency, and then outputs the out-of-phase signal
(pulse-type signal) from pin 13.
The pulse-type signal is converted into DC voltage (lock volt-
age) at the loop filter (Q101, Q102, R538, C481,...

4-5 PORT ALLOCATIONS
4-5-1 CPU (MAIN UNIT; IC19)
4-5-2 SUB-CPU (CONTROL UNIT; IC10)
Outputs reset signal for the LCD con-
troller (IC8).
Input port for serial signal from the
main-CPU (MAIN unit; IC19)
Output port for serial signal to the
main-CPU (MAIN unit; IC19)
Squelch/volume setting level input
ports for VHF band.
Squelch/volume setting level input
ports for UHF band.
Input ports for the up/down signals
from the VHF main dial.
Input ports for the up/down signals
from the VHF main dial.
Outputs...

5 - 1
SECTION 5 ADJUSTMENT PROCEDURES
5-1 PREPARATION
All adjustments in this section must be performed on wide bandwidth condition unless specified otherwise.
(Narrow bandwidth is selectable for Europe and Italy vertions only.)
Ô ÔREQUIRED TEST EQUIPMENT
Ô ÔCONNECTION
EQUIPMENT
DC power supply
RF power meter
(terminated type)
Frequency counter
FM deviation meter
DC voltmeter
GRADE AND RANGE
Output voltage : 13.8 V DC
Current capacity : 20 A or more
Measuring range : 1–80 W
Frequency range : 100–600 MHz...

5 - 2
5-2 PLL AND TRANSMITTER ADJUSTMENTS
PLL LOCK 
VOLTAGE
PLL
REFERENCE
FREQUENCY
UHF
OUTPUT
POWER
VHF
OUTPUT
POWER
FREQUENCY
DEVIATION
ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITIONMEASUREMENT
VALUEPOINT
UNIT LOCATION UNIT ADJUST
1
1
1
2
3
4
1
2
3
4
1
2
3• VHF displayed freq. :
145.000 MHz
• Receiving
• UHF displayed freq. : 
450.000 MHz [USA]
440.000 MHz other
• Output power : Low
• Transmitting
• UHF displayed freq. :
445.000 MHz [USA]
435.000 MHz other
• Output power : High
• Transmitting
• Output...

5 - 3
DC power supply 
13.8 V / 20 A
R119
UHF output power
adjustment
CP-LV
PLL lock voltage
check point
L2
PLL lock voltage
adjustment
R2
VHF deviation
adjustment
R119
VHF output power
adjustment
C84
Reference frequency
adjustment
R78
UHF deviation
adjustment
Controller 

*This output level of a standard signal generator (SSG) is indicated as SSG’s open circuit.
5-3 RECEIVER ADJUSTMENTS
The receiver adjustments must be performed after PLL ADJUSTMENTS.
5 - 4
SENSITIVITY
S-METER1
2
3
1
2
3
4
5
6
7• Turn into sensitivity setting mode.
• Select an adjustment channel by pushing 1st or 2nd
switch from the top on the left side.
• Connect an SSG to the antenna connector and set as:
Frequency : Same as displayed
Level : 3.2 µV* (–97 dBm)
Deviation : ±3.5 kHz 
Modulation : 1 kHz
•...

5 - 5
DC power supply 
13.8 V / 20 A
Controller
R229
UHF squelch
adjustment
R196
VHF squelch
adjustment
2.2 k½ JIG1 JIG CONNECTOR
1 2345678
1 2345678
4.7 k½ JIG2
to the microphone connectoror
(Sensitivity)
(S-meter)
RECEIVER ADJUSTMENTS (continued)
SQUELCH
(UHF)
(VHF)
ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITIONMEASUREMENT
VALUEPOINT
UNIT LOCATION UNIT ADJUST
1
2• UHF displayed freq. : 
445.000 MHz [USA]
435.000 MHz other
• Set the squelch level to 22 %
using the HM-98 microphone.
• R229  : Max clockwise
•...

IC1 1130009250 S.IC MN83951
IC2 1130008560 S.IC TC75S51F (TE85L)
IC3 1180001830 S.IC M5291FP
IC6 1120002580 S.IC M52338FP
IC7 1130007420 S.IC TC7W14FU (TE12L)
IC8 1190000950 S.IC SED1354F0A (QFP15-128PIN)
IC9 1130009360 S.IC LH61665AS-60A
IC10 1140007930 S.IC HD6433032SK21F
IC11 1110004910 S.IC S-80945ANMP-DD9-T2
IC14 1180000420 S.IC TA78L05F (TE12R)
IC15 1180001850 S.IC TA79L15F (TE12L)
IC16 1120002600 S.IC M52045FP [EUR], [ITA]
1120002590 S.IC M52042FP other
IC17 1180000420 S.IC TA78L05F (TE12R)
IC19...

R240 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R241 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R242 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R243 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R244 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R245 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R246 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R247 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R248 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R249 7030003560 S.RESISTOR ERJ3GEYJ 103 V (10 k½)
R250...

REF ORDER
DESCRIPTION
NO. NO.
C121 4310001070 MYLAR 100 SMC 333K
C122 4030014540 S.CERAMIC GHM1038 SL 330J 3KV
C123 4510006970 S.ELECTROLYTIC ECEV1CA330WR
C124 4030006860 S.CERAMIC C1608 JB 1H 102K-T-A
C125 4510006230 S.ELECTROLYTIC ECEV1EA470UP
C126 4030006860 S.CERAMIC C1608 JB 1H 102K-T-A
C127 4030006860 S.CERAMIC C1608 JB 1H 102K-T-A
C128 4510006970 S.ELECTROLYTIC ECEV1CA330WR
C129 4030006860 S.CERAMIC C1608 JB 1H 102K-T-A
C130 4030006900 S.CERAMIC C1608 JB 1E 103K-T-A
C131 4030006900 S.CERAMIC C1608...