Icom IC-781 (IC 781 IC781) transceiver mods reviews software and diagrams

   
 
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24 June 2019, 13:48 UTC 


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Icom IC-781 (IC 781 IC781)
IC-781
Programming interface schematics for Icom:
Programming software for Icom IC-781 (IC 781 IC781) :
PDF User Manual for Icom IC-781 (IC 781 IC781) :Icom IC-781 Instruction Manual
PDF Adjusments Procedures Manual with schematics for Icom IC-781 (IC 781 IC781) :
Schematics for Icom IC-781 (IC 781 IC781) :

Mods for Icom IC-781 (IC 781 IC781) :
    Icom IC-781 (IC 781 IC781) filter modification
    Icom IC-781 (IC 781 IC781) Reduce the internal heat by the speaker
    Icom IC-781 (IC 781 IC781) ALC Circuit problem
    Icom IC-781 (IC 781 IC781) General coverage transmit mod

Icom IC-781 (IC 781 IC781) technical specifications :  Icom IC-781 (IC 781 IC781) technical specifications



Icom IC-781 (IC 781 IC781) filter modification

The stock FL-96 (455 kHz SSB: 2,8 kHz wide @ -6 dB) can be replaced with an FL-44A (2,4 kHz wide @ -6 dB) to improve adjacent-channel selectivity and sharpen Twin PBT operation. In addition, the stock FL-102 (9 MHz, AM) can be replaced with an FL-223 (9 MHz SSB: 1,9 kHz wide @ -6 dB) to provide an SSB-NARROW bandwidth setting.

Here is the filter installation procedure:

(I would suggest that you purchase an IC-781 service manual from Icom Parts for guidance, if you do not already have one. Icom Parts should also have the FL-44A).

  1. Remove the top and bottom case covers.

  2. Lay the radio upside down on a towel, with the front panel facing you.

  3. Using a magnetic-tip manual screwdriver with a #2 Phillips tip having rounded blade edges, remove all eleven retaining screws from the IF board (the board with all the filters).

  4. Unplug the multi-conductor header cables from the board, to allow the board to be moved aside.

  5. Grab the inner edge of the board, and swing the board away from the chassis. Do not stress coax cables on board. Rest board on a stand (e.g. 2 phone books) next to radio.

  6. Locate FL-96. Using a solder-sucker or wick, and a temperature-controlled pencil iron, desolder 4 filter pins.

  7. Remove nuts & washers from filter mounting studs. (I think the nuts are M3 or M4.)
  8. Remove FL-96, wiggling it gently to free pins. You may need to re-heat pins quickly to release filter. The board is G-10, and can take reasonable heat.

  9. Place FL-44A on board; tighten down studs with nuts & washers.

  10. Re-solder pins of FL-44A; clean excess flux with nylon brush & isopropyl alcohol. Also ensure that there are no solder blobs or slashes.

  11. Re-install board and all cables unplugged in Step 4.

  12. Pull FL-102; insert FL-223, and flip 2 dip switches (per user manual) from AM to SSB.

  13. Test radio, then replace covers.

Good luck! The whole job should take about 30 minutes.Note that the FL-223 is selected in USB or LSB mode by pressing the [WIDE] button.

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