Does anyone know if the tsu 9600 and tsu 9400 rotary wheel are interchangeable. I have a problem with screen backlight, has a mind of its own going on and off without touching unit. Switched firmware multiple times no fix . I read an old thread talking about rotary wheel being the culprit. If i move wheel ever so slightly and don't touch it problem goes away. I have an old 9400 with metal wheel. 9600 has plastic with dots, can they be switched. If so is there any soldering involve. Thanks