MacBook Pro wont turn on, completely anyway...

Ok so here is the situation...

2012 macbook pro retina 2.6ghz, 8gb ram, a 512gb samsung 850 in the 2.5" slot and another of the 850's in the drive bay.

I bought a 2015 macbook pro and stop using the old macbook for about 3 months....

I figure id use the 2012 as a media server, but when i tried to turn it on, i got nothing.

Heres what ive checked...

Battery:

Does hold a charge, does charge properly with the magsafe.

SMC reset:

It works, so that means I can rule out the logic board right?

Power cycle:

Havent gotten any results from this either.

Target mode:

no thunder cables on hand, will wait til morning to get one.

Display:

No minidisplay to hdmi on hand, so ill have to check in a few hours...

(display does not turn on in any capacity whatsoever. Connector is clean and properly inserted.

Keyboard:

I assume this works because i am able to run the SMC reset...

Trackpad:

no way to verify as of now.

HERES THE WEIRD PART...

When put a usb drive, it worked, at first i thought everything was all bad and maybe water got on or in somewhere, but then i held the power button and the device turned off (hdd spun down) Pressed power button with it in, and it spins up as if the computer was starting.

As far as the disc being accessed, i have no idea if it is, Sure sounds like its checking the disc though.

Other than that, I have no lights on the computer itself that work aside from the left side battery indicator. (works fine)

I actually didnt think the power button worked until i triggered the power pads to make it trigger "on"

so... Anyone have any idea of what I can do to troubleshoot further? Cause im starting to not know what to do...