MacBook Pro black blank screen with fan full speed

Have a Macbook pro mid 2010, the system was initially slow so tear down and applied thermal paste on the GPU and CPU, system behaved very good after assembly.

While working on the macbook accidentally unplugged the power adapter then it went to blank screen immdediately.

Pushed the power button to hard shutdown and restarted , now my display gone black blank screen.

Scanned all the forums and suggested answers for the past one week but no success

1. Flashlight on Apple logo for login option but couldnt see anything

2. Tried NVRAM and SMC reset multiple times , but nothing

3. Drained the battery and left for overnight and connected the power next morning still no luck

4. disconnected the battery and used only power adapter source but still nothing

5. Pressed recovery option

When i press the power i get sleep light going strong, hard drive working, fan full speed and thats all nothing else

Not hearing any startup chime, now running out of option and not sure what to do next

Someone please help.