I know this is an older post but I thought I would add to it for anyone that comes across this issue in the future. I’ve seen this problem in another S controller where that component (labelled D23) on the power board will fry and the controller will no longer turn on. I’m not a technician by any means but the controller was no longer under warranty and I was curious, so I removed the burned part from the board and soldered on an intact one that I desoldered from another busted controller. After putting the controller back together with fresh batteries, it powered on again! However, it immediately started to overheat in that region and I turned it off to avoid frying the replaced D23 component. The question remains: are the D23 components defective? Or, is there something else in the circuit that is causing D23 to overheat? If anyone who is experienced with electronics has any suggestions, I certainly welcome them.