I have not read the whole thread (Yes bad of me) but your opening post and the couple that followed made me think of one thing that has been a issue for me in the past years ago. PCS were right to replace the battery and also had reason to say it may be your electrics.
The only thing I can think of is that for some reason I do not know your battery is not working correctly on the motherboard and storing the bios information (This is what the battery is for, it generates enough power to store the bios information) so when this happens and you boot the system up the bios will revert to the default settings and unfortunately the default settings in this case have the LDVS setting to disable the main screen.
The only way I can see this being a repair if that is something your still looking for would be to have the motherboard replaced. A way to see if this is happening is if you can get into the BIOS check to see if the clock is still correct or if it has reset to 00:00:00
Please if anyone feels this is wrong correct me It's late it I am trying to remember a very old issue I had that this reminds me of.
The only thing I can think of is that for some reason I do not know your battery is not working correctly on the motherboard and storing the bios information (This is what the battery is for, it generates enough power to store the bios information) so when this happens and you boot the system up the bios will revert to the default settings and unfortunately the default settings in this case have the LDVS setting to disable the main screen.
The only way I can see this being a repair if that is something your still looking for would be to have the motherboard replaced. A way to see if this is happening is if you can get into the BIOS check to see if the clock is still correct or if it has reset to 00:00:00
Please if anyone feels this is wrong correct me It's late it I am trying to remember a very old issue I had that this reminds me of.