Purpose
The built-in IC-746 electronic keyer speed is adjustable over the range of 6 to 60 wpm. Most amateur radio operators never operate Morse code approaching 60 wpm. I usually operate in the 15 to 25 wpm range and found that setting the keyer speed in this range is very touchy because the speed changes greatly with only a slight rotation of the Key Speed knob. This modification limits the maximum keyer speed to about 32 wpm making the adjustment of the keyer speed easier.
Modification
Solder a 1.5k ohm resistor across C8 of the S-LOGIC Unit PCB. If a maximum keyer speed other than 32 wpm is desired, increase the resistor value for a higher maximum speed, or lower it for a lower maximum speed.
Procedure
- Remove the top cover: 12 black screws and 2 chrome handle screws
- Remove the bottom cover: 6 black screws
- Remove the front panel assembly: 4 flathead screws; disconnect ribbon cable W18 that connects the S-LOGIC Unit PCB on the front panel assembly to the MAIN Unit PCB on the chassis by pulling it out of its socket (J1334) on the MAIN Unit PCB
- Solder a 1.5k ohm resistor across C8 of the S-LOGIC Unit PCB. C8 is located next to pin 1 of J601. See photograph for location (red arrow). I used a size 0603 surface mount resistor. A leaded resistor may alternatively be used.
- Reassemble in reverse order of disassembly.
 
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