That amber light only confirms the board is receiving 5V power.  It needs a 12V rail to start up.  Usually a solid amber light means a bad power supply.  The other possibility is that the mainboard is bad -- and given the age of the system, if you plan a repair, it may be wise to replace both the power supply and the mainboard together, since they're the same age.  
I have a Dell optiplex 3020 and it is not coming on it is just showing the orange light on the motherboard no fans spinning too please help me with it!
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