Modifications for the ICOM - RogerK

19-07-1998(IC-736) Icom IC-736 DDS/VCO Bug/FixI have just received confirmation from ICOM Canada that there is a bug in the design of the IC-736 with respect to frequencygeneration. It seems that although it seems to be a common problem, not all IC-736's exhibit the problem. It seems that there isa "floating" data/address line and at times it floats the wrong direction, giving about 30HZ (maybe 32HZ?) difference in LSBmode. The fix is to solder a 47K resistor between pins 17 and 10 on IC24 on the main board. (bottom of radio, near front). Ihave not yet tried the fix, as I just got it today.To see if you too have the problem, try the following test:1. switch to AM first and tune to a strong AM carrier, and switch to LSB (once and only once) 40M is a good place to try this.2. tune the carrier to about 400HZ tone and listen carefully.3. switch to USB and back to LSB quickly. You should hear a different tone. If not, then you are "floating" in the rightdirection.4. switching to USB and back to LSB will not produce any more differences. You must LEAVE SSB mode (ie AM) and comeback to LSB for the first time to re-set the "floating" line. It is the LSB/USB/LSB switch that shows the difference in the twoLSB received frequencies (by tone only, the display does not change...)I've tried to post this message about 4 times so far with no apparent success. Hopefully this one will make it....73's and hopethat helps someoneSteve, VE3CWJThis modification is read 903 times.top of page23-08-1998(IC-737) Icom IC-737 general coverange in transmission1. Remove the top and bottom covers of the transceiver.2. Remove the final power amplifier module.3. Locate the LOGIC-UNIT on witch there is a back-up lithium battery for the RAM memory.4. On the LOGIC-UNIT, near the chip called IC6 (TMP82C265BF-2),between the output pin PC06 and the imput pin PA15, findthe diode D3.5. This diode is not an SMD component.6. Cut the diode D3...Now the ICOM IC-737 will transmit from 1,6 to 30 Mhz !!!.73's de IW3BKW Riccardo @OE7XCI. ***This modification is read 1061 times.top of page23-08-1998(IC-737) CW Filter Switching Modification for the Icom 737The Icom 737 is a wonderful radio for CW operation, but I did not like the filtering switching options offered in normal operationof the radio when you have installed BOTH the 9 Mhz and 455 Khz optional CW filters. The default option is to use the SSB filterfor CW in the CW mode, and then switch in BOTH the 9 Mhz and 455 Khz optional IF filters in the CW-N mode. This provides toobroad a filter for general tuning in CW, and the CW-N mode (with the two filters in) is far too sharp for just tuning around.I felt that it would be better to allow the 455 Khz filter to be functioning full time in the CW mode, and then switch in the 9 MhzCW filter in the CW-N mode. The following simple modification only requires a single wire to added to the radio.MODIFICATION1. Remove the top/bottom cover of the radio as per the manual.