JRC JMA-5206 Instruction Manual page 312

3) Light
Checks for the operation panel light.
Procedures 1
Exit 1
Press [3] key while the Keyboard Test
menu is open.
The brightness of the operation panel is
gradually intensified at four levels.
Press [RADAR MENU] key.
The menu will be closed.
8─11
Keyboard Test
1. Key Test
2. Buzzer Test
3. Light
0. EXIT