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.