I have a G751JM laptop. I'm on my second power supply. First one eventually would not charge unless I would unplug the power supply and plug it back in. During that time I noticed my fps in games where very low, close to unplayable. I thought that it was just my laptop needed to be cleaned up. After a couple of months the power supply just died on me. I purchased a new one and when I plugged it in i noticed my fps in games where back to normal. I am now having the same issue with the second power supply.
Randomly its not charging while it plugged in. When this happen I have to unplug and plug back in to get it to charge. Also now my games fps are very low while plugged in. Anyone have this issue?
Although it may not be the problem in this case, still sounds like the symptoms of a bad AC adapter, but requires more investigation to be sure.
If you game on battery, the performance will drop, so sounds like when your AC adapter stops working, you are gaming on battery with lower performance?
If you haven't already, whenever you start seeing problems, confirm if you AC adapter is being recognized by your notebook through the icon on your taskbar which will indicate whether you are on battery power or not.
If your notebook keeps switching to battery power when the AC adapter is connected, check your notebook power jack to make sure it doesn't feel loose, and confirm the output rating under your AC adapter matches the input rating under your notebook which should be 19.5 V DC, 9.23 A, for 180 W.
Although it's just a temporary workaround if it works, try to keep your battery at 100% and charge your battery completely when the notebook is off to minimize stress and power draw from your AC adapter while the notebook is turned on.
If anybody else has better ideas, hopefully we'll hear from them. Thanks.