Dark Display after replacement w new

Daughter's MacBook Core 2 Duo...had "half screen" issue...would clear with pressure on bottom Rt corner...replaced display cable, then replaced display after cable did not fix issue...

Booted up ok screen displayed normal for 20 seconds then went black...can see screen with flash light.....now I'm reading the inverter cable could be bad...

I'm sure its possible I damaged the cable but was very delicate with whole repair.

Is there any test I can do to eliminate the cable or inverter or could this be something else.

thanks for any suggestions...this is giving me a stiff neck if you know what mean.