In some circumstances it may be helpful to perform a factory default reset on the unit.  This can be done by powering on the RDG-1520/RT-09, then press SETUP on the remote. Scroll down and select FACTORY DEFAULT and press SEL on the remote to select it. Press SEL, then DOWN on the remote so that the cursor is highlighting "Yes" on the Module section of the Reset menu. Then press SEL. Immediately after doing this, press SETUP again and go back to the FACTORY DEFAULT menu. This time, just press DOWN on the remote so that "Yes" is highlighted on the Main option, and press SEL to reset it.