What are the possible causes of an overheating CPU and MCP

Hello

After connecting a defective LCD cable on two macbooks A1304 I had no image and the CPU overheats enormously

This cable has probably short circuited a few items ...

After observing the two motherboards I noticed a transistor HS on both the Q9807 serving fueled the backlight

So I replaced these two cards but the problem is always the same :

-No Screen image

-No Startup chime

-The CPU and MCP overheating enormously

As I am not an expert in this field I prefer requested

What are the possible causes of an overheating CPU and MCP after a short circuit ????

thank you in advance for your assistance

Mother board model : 820-2375