Hello. I have a Dell Optiplex 380 MT that isn't powering on. The light shows amber on the motherboard but the front I/O is not showing any errors and the machine does not power on.

I've tried:

Replace CMOS battery

8 different RAM modules (4GB each)

3 different PSUs (pulled from other working 380s)

Replaced the processor

Reseating all cables

Tried powering on with GPU and drives disconnected using VGA

Is the motherboard dead?