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IC275.3
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1990-10-14
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199 lines
Model: IC-275
Division: Amateur
Note: This service bulletin is meant for technical per-
sonnel with experience working on solid state com-
munications equipment. Damage caused by im-
properly installing this modification may cause
ICOM to charge for subsequent repairs to the
product. ICOM does not warrant this modification.
Bulletin #: 588-001
Subject: If the IC amplifier oscillates when the noise
blanker is turned on and the FL-83 CW narrow fil-
ter is installed
Procedure
1. Remove the covers to gain access to the main circuit board.
2. Remove R354 (22K) from the main circuit board and replace it
with a 10K (ICOM P/N 915-01113) resistor.
3. Re-install the main circuit board and replace the covers on
the radio.
Bulletin #: 24487-002
Subject: Prevent PLL unlock at high ambient temperature
Procedure
1. Change the following parts on the PLL board
Original New
Part Value Value
C101 12 pf 50V CH 6 pf 50V CH
R137 35D 45 SN (ICOM P/N 915-04229)
R133 22K 15K
C191 3 pf 50V 6 pf 50V
2. The thermister should be installed in series with R133. Un-
solder one end of R133 and solder R137 in series with it.
Bulletin #: 24487-005
Subject: Improve voice synthesizer and side tone audio
Procedure:
1. Remove C214 (.47 uf capacitor) from the main board.
2. Install a .1 mf 16V barrier layer capacitor in series with a
2.2 K 1/8W resistor from the emitter of Q58 and the base of
Q59 on the foil side of the board.
Bulletin #: 24487-003
Subject: Prevention of PLL unlock at 174 MHz
Procedure
1. Remove and replace the following components on the PLL Board
Original New
Part Value Value
R130 120 Ohm 270 Ohm
R131 47 Ohm 18 Ohm
R132 120 Ohm 270 Ohm
C42 60 pf 50V 30 pf 50V
C47 43 pf 50V 62 pf 50V
Bulletin #: 24487-004
Subject: Improve the stability of the center meter
Procedure
1. Replace C81 on the main board (currently 120pf 50 CH type
capacitor) with a 120 pf 50V SH temperature coefficient
capacitor (ICOM P/N 918-05960).
Bulletin #: 24587-001
Subject: Noise coming from speaker during transmit with
audio turned up.
Procedure
1. Replace R125 (currently a 47K resistor) on the main board
with a 10K resistor.
Bulletin #: 6888-001
Date: March 8, 1989
Subject: If CPU noise occurs
Procedure
Write to ICOM's Customer Service department for a copy of
this service bulletin.
Bulletin #: 13889-019
Date: May 1, 1989
Subject: Eliminate possible spurious emission when thermal
switch has turned on during transmit
Procedure
1. Remove top and bottom covers.
2. Remove PA section from radio.
3. Remove shield from power amplifier.
4. Replace R7 (originally 10K 1/4W) resistor with a 1K 1/4 watt
resistor (ICOM part number 915-01165).
5. Replace R8 (originally 10K 1/4W) resistor with a 1K 1/4 watt
resistor (ICOM part number 915-01165).
6. Replace the shield on the PA section.
7. Replace the PA section in the radio.
8. Replace the top and bottom covers.