RB1100 cannot boot up

All,

My RB1100 suddenly won’t boot up, I try restart several times but it still Freeze, NO Beep sound and yellow led still on.
Do you know how to fix it.

Have you tried plugging in a serial cable?

Not yet, still find out the cable.

so what should I do if I can access trough serial?

Find out where it is getting stuck in the boot sequence. You will probably have to do a netinstall.