Help No Display but Fans Spin etc

Help No Display but Fans Spin etc

So it didn't work at first,

then i messed around cant remember what i did but it started working after opening for a while then i opened again to put things better in place.

It has a blank display not connecting to HDMI, but powers up, fans spin etc.

I have tried hairdryer, cleaning MOBO, External Monitor, Heating GPU, Taking both batteries out,, Power for 60 secs etc.

Is there an multi meter test i can do to see if its the GPU e.g. not getting enough power.

I'm unsure.

Is there any motherboard test i can do or buy a motherboard diagnostics card etc.

I would like to find out problem if possible.