Icom IC-740 (IC 740 IC740) transceiver mods reviews software and diagrams

   
 
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26 February 2021, 4:31 UTC 


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Icom IC-740 (IC 740 IC740)
IC-740
Programming interface schematics for Icom:
Programming software for Icom IC-740 (IC 740 IC740) :
PDF User Manual for Icom IC-740 (IC 740 IC740) :Icom IC-740 Instruction Manual
PDF Adjusments Procedures Manual with schematics for Icom IC-740 (IC 740 IC740) :
Schematics for Icom IC-740 (IC 740 IC740) :

Mods for Icom IC-740 (IC 740 IC740) :
    Icom IC-740 (IC 740 IC740) FM-Unit EX242 zum (selber) nachbauen
    Icom IC-740 (IC 740 IC740) enable TX on WARC bands
    Icom IC-740 (IC 740 IC740) Display/distortion problems IC-740 HF rig

Icom IC-740 (IC 740 IC740) technical specifications :  Icom IC-740 (IC 740 IC740) technical specifications



Icom IC-740 (IC 740 IC740) Display/distortion problems IC-740 HF rig

Also probably would apply to IC 735 and IC 745 as well.

The symptoms were distortion on transmit, a very unstable display, often tuning dial would not move frequency, display would give all kinds of random numbers, sometimes no numbers at all on sections of display readout. This appeared to be a mechanical problem, as a sharp "rap" on the case would change things, sometimes curing it temporarily. We pulled off the covers of the set, and gently tapped each board. The PLL board appeared to be the culprit. This is the small covered board to the rear left on the underside of the 740.

We popped off the little cover over the board, loosened the 4 mounting screws and took out the board. Everything looked good, but the points on the board that contacted the metal standoffs were corroded and dirty. We flowed fresh solder around the screw holes on the board (underside), cleaned the standoffs and cleaned the chassis where they connected to it. This cured the problem. Interestingly enough, we did the same fix to an Icom 22S 2 mtr rig several years ago that would keep going out of "lock". It cured that problem as well. The bottom line is, make sure all your board to ground/chassis connections are real clean. Just a thin film of crud can cause all kinds of problems on a unit that uses the mounting screws as the ground return. Sometimes (but not always!) just loosening and retightening the mounting screws will help the problem.

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