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Modifications for the Icom IC-765

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Modifications for the Icom IC-765

19-07-1998 Icom IC-765 improved monitor volume
19-07-1998 Icom IC-765 Passband tuning mod
19-07-1998 Mod to prevent ant sw unit failure
19-07-1998 Adjustment the mortrs control unit
22-08-1999 IC-765 Extended TX Mod
04-06-2000 Replace 455 SSB filter w fl 44a very nice selectivity

19-07-1998  
Icom IC-765 improved monitor volume
     

For radios with serial numbers below 2000
  1. Set radio for 8 mhz in LSB
  2. Adjust C226 for 1 to 1.2V at R201.
  3. Verify that it goes to 3V at 7.9999MHz

Change R85(10K) on main unit to 4.7K.

 

19-07-1998  
Icom IC-765 Passband tuning mod
     

  1. Dessolder and lift cathode of D63 from PCB.
  2. Add a 1N914 diode to the junction of the 1N914 cathode and the D63 cathode.

After modification: If shift button out = pass band tuning
If shift button in = if shift.

Date: 28-01-2002 User comment From: Carl Severa, AH8I
Subject: Icom 765 Passband Tuning Mod (addition of)
Your PBT modification for the IC765 is not complete.
Please refer to your source and read what is on your website.
I do not have it or I would give you the correction.
Carl Severa
 

19-07-1998  
Mod to prevent ant sw unit failure
     

  1. Remove top cover

  2. Locate ant sw unit at right rear of radio (at antenna jack).

  3. Solder a .0047 uF, 500v ceramic capacitor to back side of pc board as shown. (Board removal is not necessary).

  4. Reinstall top cover and check for proper transmitter operation. this modification prevents failure of R1, R2, D1 and L1.
-------------------------------------- Top edge of board

                     /0
                   /                       Rear panel of radio---->
   I----0        /         
 __I__         /             
 .0047uF     /0_______________0
 --I--  0                                  /0/
   I       ________________________       / /
   I------0________________________0     / /
                                        / /
                                       /0/


         View: back ant sw unit pcb.


 

19-07-1998  
Adjustment the mortrs control unit
     

The feedback circuit that controls the tuning motors becomes sensitive after a few months of ageing. It requires a one time adjustement to correct.
  1. Remove top cover and locate the antenna tuner board.

  2. Locate r5 and R10 and set them to the center of their range.

  3. Set radio as follows:
    Tuner on
    Frequency 14.100 MHz
    Mode RTTY

  4. After transmit is engaged for 30 seconds,

  5. Adjust each control (R5 and R10) so neither motor tunes while changing from SSB to RTTY and back to SSB.
    Note:
    R5 (right) controls right motor and R10 (left) controls left motor.

  6. Repeat this adjustment to verify proper operation and then check on all other bands.

  7. Reinstall top cover and return to operation.


 

22-08-1999  
IC-765 Extended TX Mod
     

  1. Remove top and bottom covers

  2. From the bottom of the radio locate the matrix board which is next to the front panel.

  3. Find diodes D50, D51, D52, D53, D54 and D55.

  4. Cut one leg of D53

  5. Assemble the radio and stay legal!


 

04-06-2000  
Replace 455 SSB filter w fl 44a very nice selectivity.
     
Author: Chris - Blakhart@huntel.net.MODIFICATION.NET


Cut power switch line and wire for on at all times-never lose s-meter lamp again. Better yet pull ps out and rewire for external use to keep heat out.

Replace AM rect diode w schottky for better audio.

Increase prod. detector output cap w larger value to get more bass.

Adjust audio tone contrl for minimum hisssss.

Take out speaker to let heat out-its a killer.

Date: 19-01-2002 User comment From: Chris
Subject: More info
The fl44a is direct replacement for the fl96 stock 765 ssb filter. If one replaces the 9 meg fl30 filter with an fl80 you then have a 2.3 bandwidth filter with outstanding specs per ICOM. All parts are ICOM standard parts, find em used.

Another even more important tip is to replace C-280 with a 0.82mf cap (observe polarity if need be)and the agc pops are gone and the IMD per QST of DEC 95 pages 78 to 79 are very relevant.