Icom IC732 modification - open ham bands

Icom IC-732 is a version of the well-known IC-737 meant for Japanese domestic market. That means its transmitter is locked to whatever band limits were allocated to Japanese hams in the 90s. They were certainly more strict than current regulations in region 1, meaning a ham who bought this transceiver cannot make use of, for example, a good portion of the 80m band.

I am one of the (now) happy owners of the 732. Apparently, I haven’t done my homework when buying it several years ago… :)

Fortunately, as the IC-732 is basically a software-locked 737, it can be easily unlocked. There are two modifications that can be done - there are 2 diodes on the main board that limit the bands: D3 and D4. My radio originally had been locked. Cutting D4 opens the radio to all amateur bands (except 60m). Cutting both D4 and D3 will probably open it up completely, but I havent’t tried that.

OK. How to do it?

1. Grab the schematic
2. And the service manual for IC-737
3. Disassemble the radio according to the service manual to get to the PLL unit - interesting diodes are there
4. Find the diodes (they are close to the front panel side of the PLL board)
5. Cut the lead from D4 (it’s a through-hole component, mounted vertically on the board)
6. Reassemble the radio
7. Reset the CPU (ENTER + CLEAR on power-on)

Now the radio should transmit on following ranges:

• 1.8-2.0 MHz
• 3.4-4.1 MHz
• 6.9-7.5 MHz
• 9.9-10.5 MHz
• 13.9-14.5 MHz
• 17.9-18.5 MHz
• 20.9-21.5 MHz
• 24.4-25.1 MHz
• 27.9-30.0 MHz

Good luck and 73!