Hello, I just encountered a problem with my Tecsonic MX-900. The on/off button won't stay down! The box will only power up when I hold the button down, but it won't lock in the 'on' position. Before I try to buy a suitable replacement component, I need to access the inside of the switch to see why it's not locking, but I can't see how to open it up. Here's the offending switch, can anyone please help??