Aspire 4720Z charging problems.

A while back the laptop was dropped & the power jack was broken. I ordered a new one & replaced it. Eventually, due to the plastic ring that encompasses the charging plug being broken, the jack broke again. At this point the laptop would no longer turn on whether it was plugged in or not. After disassembling it I noticed the charging board was burnt so I replaced it. At this point it would run but not charge so I replaced the battery. With the new battery in & charger plugged in the screen flashes from bright to dim repeatedly & it goes from charging to not charging in tandem with the flashing screen. It will do this as long as the battery is in. Once the battery is removed it stops. Thinking I got a defective battery I got another new battery & it does the same screen bright to dim & the same plugged in not plugged in thing.

This is where I'm at now. I read a few places concerning other laptops of varying types that it could be the charging circuit that is bad & seeing that it has been dropped & the power board had been burnt out, I wouldn't doubt it . I do not know if the circuit is in the motherboard or the power board that is plugged in adjacent to the motherboard. The power board was replaced but it could be malfunctioning/bad. I can get either the motherboard or charging board for $50 or less but would rather not buy both & waste the extra $50. Anyone have any insight?

Oh, also I have tried 2 separate chargers & the same thing happens with both. Both chargers work properly with a 4620z that I own.

After a bit more testing I have noticed that the Charging Light on the laptop does not light up when plugged in. Also, the adapter has a light on it (always green) and as the battery symbol switches from battery to charging , the light on the adapter dims a bit. This shows me the 2 states. State 1: the screen brightens, the battery symbol says plugged in & the adapter light dims it is actually pulling current & charging. State 2: screen dims, battery symbol says battery (only) & the adapter light brightens which means it's pulling no current & not charging. It then rapidly switches between these 2 states.

Not sure if this helps to pinpoint the problem. I would also like to find schematics for the motherboard if anyone knows where to look. I'd like to manually fix the board if possible. No matter what I am ordering a new motherboard but would like to use this opportunity to learn how to fix the problem. I can also use this knowledge to repair other motherboards rather than replacing them. Thanks.