21.5” late 2009 iMac work except Inbuilt display

I have 21.5” late 2009 iMac with 3.6ghz processor, 4gb ram.

I am from low economic group. I got this as donate.

When I bought This Used system, it was with incomplete OS X & Dead NVRAM battery.

1. I tried multiple times to install OS X with bootable Usb.

2. Reset smps

3. Prvm ram, clean physical ram. But installation showed multiple errors.

4. I connected to Apple help via call. Shared some articles but not fixed.

Problem started when I take help from technical person when he changed nvram battery.

1. Display stop working.

Then I can’t afford technical help so I decided to make it myself.

Before started Something I spent 2 months On various articles, Videos, faqs.

I found broken lvds cable and vertical sync cable while during nvram battery Change.

1. Replace same number lvds cable & vertical sync cable successfully without damaging anything.

2. Re greese both processors successfully.

3. Successfully Installed Mac OS X & upgraded.

4. Made Dygnotic  led worked.

5. Successfully installed other softwares.

6. System working fine on external display. With chimp sound.

Problem:

1. Unsuccessful To start Inbuilt display Again.

2. Multiple times checked cable connections. But unable success.

3. Display showing dark black, but I tried with torch it showing light visible display Elementals on screen.

Need help,

? Is this Lvds cable problem?

? Is this 12 volts display supply problem?

? Is this lcd led inverter board problem?

? Is this CFL tube inside lcd panel problem?

I know Without checking patients you can’t diagnose.

thank you!