Laptop on death's door?

Hey r/techsupport

I have an old inspiron 7720 laptop that has been a workhorse for me for the last few years. The battery life has slowly died and the processing speed has slowed down over the years but she's held relatively steady.

A few weeks ago, when i turned the laptop on, it died. I figured it just needed plugging in since the battery life is terrible. That also didnt solve the problem. I grabbed an old (identical) adapter, figuring the laptop adapter might have gone (even though the led indicating it is getting power was on) - still no fix.

So i pulled the battery and tried both adapters and still, no power. So i did some googling and thought maybe its the DC power supply. I purchased an OEM DC power supply online and installed it. Still no fix.

Im not sure if this means I'm sunk and its a motherboard issue? I really cant afford a new laptop, unfortunately. Any other diagnostic tests or suggestions you all could make would be greatly appreciated.