Inspiron 3668 motherboard swap

I had this board that does not power off when shut down hard or soft. When connecting a power cord to it it used to make a loud fan noise.

After CMOs battery replacement and reset CMOs no change. The only way this board can perform or behave quasi normally is never shut it down. I recall it does sleep after long idle. 
Finally I found a discarded unit of 3668 from which a replacement board is salvaged and swapped in this unit, then all above issues gone. Lesson learned