A friend gave me a old FT-290r with the display broken. This i common problem, the display starts showing stains and eventually turns black completely. So I decided to replace the display. I found on the internet a solution in which the display is replaced by a small OLED and an additional CPU to translate the commands from the Yaesu CPU for the old display to the new one.

However, I decided however for another approach: a complete rebuild of the CPU board. This way, I am completely free in changing or adding functionality laike CAT, CTCSS tones and various stepsizes. Also, in one tranceiver I replace the complete PLL by a small board with an SI5151. This works great too.

I chose for a standard Arduino nano. So, disassemble the transcever, remove the display and CPU board. Replace the display with a small OLED for which Adafruit has developed a library, the SDD-1306. Please take care to choose the right options with the proper #define: FT290 (default] or FT790 and original PLL (default] or SI5351 (only for the 2m version].

Cut out a new board of experiment board the size of the original CPU board, and remove the connectors from the old one and put hem in place on the same location on the new board. Solder the Arduino on the new board. The location is a bit critical since you would like to keep access to the USB connector when it is build in. Furthermore, you need a PCF8574 (I use the smd version] and find a spot for the original beeper. Notice that the CPU board in the FT-790 is slightly different.

To extend the IO for the buttons, mode switch and memory switch I included a PCF8574. To select the appropriate set the signals R42 (mode] and R43 (buttons] is used.

The software includes a CAT-handler so when everything is done and build in, the USB connector of the Arduino can be led to the external world. I use a beafy USB-A connector for this, which I've glued in the hole for the antenna connector (since I replace this one with a BNC connector to the front panel].