Logic board failure, green light on magsafe

My Macbook pro mid 2012 retina simply switched off while i was using it. One second i was typing a document, then the next the screen was black. The laptop does not respond to power button, i have tried resetting SMC, PRAM, powering using power pads on logic board. powering by removing the battery leaving only magsafe connected, unfortunately all of these failed to turn on the laptop. The only sign of life is that when the magsafe is connected to the logic board the LED goes green for about a second, then goes orange (no battery connected).

I have a fairly limited knowledge of electronic circuitry however i know how to use a multimeter properly and have access to all the tools required to replace individual components.

After a bit of research i found out it was necessary to test the various power rails, this is about as far as i am able to get because i do not have an understanding of how each power rail relates to each other and which power rail relies on which etc.

I downloaded the schematics for my logic board (820-3332-A) and board viewer software and set about testing every power rail in the hope that someone on a forum may be able to point me in the direction of what to test next.

Thankfully this is a work laptop but it is top spec and ran like a power house before this happened so i am eager to get it working again.

Below are my results. All conducted with logic board removed from pc, powered by confirmed working 85w psu.

PPBUS_G3H= 12.6

PPVIN_S5_HS_COMPUTING_ISNS=12.6

PPVIN_S5_HS_GPU_ISNS=12.6

PPVIN_S5_HS_OTHER_ISNS=12.6

PP18V5_DCIN_CONN=16.3

PPDCIN_G3H =16.5

PPDCIN_G3H_ISOL=16.5

PP3V42_G3H=3.4

PPVRTC_G3H=3.3

PP5V_S5=5.015

PP5V_SUS=5.01

PP5V_S4=0

PP5V_S3=0

PP5V_S0=0

PP3V3_S4=0.12

PP3V3_SUS=3.3

PP3V3_S5=3.3

PP3V3_S3=0

PP3V3_S0=0

PP3V3_TBTLC=0

PP1V05_TBTLC=0

PP1V05_TBTCIO=0

PP15V_TBT=0

PP1V8_S0=0

PP1V8_S0_CPU_VCCPLL_R=0

PP1V5R1V35_S3=0

PP1V5R1V35_MEM=0

PP1V5_S3RS0_CPUDDR=0

PP1V5_S0=0

PP1V5_S0_RIO=0

PPVTTDDR_S3=0

PP0V75_S0_DDRVTT=0

PP1V05_SUS=1

PP1V05_S0=0

PP1V05_PCHVCCIO_S0=0

PPBUS_SW_BKL=0

NC_SMC_T25_EN_L=n/a

PP1V05_S0_P1V05TBTFET=0

PP3V3_S0GPU=0

PP3V3_S0GPU_MISC=0.34

PP1V5R1V35_S0GPU=0

PP1V0_S0GPU_ISNS=0

PPVCORE_GPU=0

PPVCORE_S0_CPU=0

PPVCORE_S0_AXG=0

PP1V5_S3_CPU_VCCDQ=0

PP1V05_S0_CPU_VCCPQE=0

PPVCCSA_S0_REG=0

Thanks in advance for taking the time to read!

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