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Yes PLT_RESET_L pulses now but still no boot, Fan does not even attempt to spin with SMC bypass

so update on this unit. today it decided to boot. ran cpu stress test and no issue... made no changes since last update. *scratching head*

now i get a pulse on pin 3, still not turning on. whats next?

no corrosion in the area, no pulse on pin 3,6. pulses on pin 5,7 on u1950

no issues getting into diagnostic mode without SSD plugged in. no luck with SSD plugged in and SMC bypass as well

***you can ignore this*** i'm measuring pp3v3_S0 @ 1.9V. is this right? i'm not even getting p3v3s0_EN always on how is there even voltage here @@?

can't find PLT_RST_L, hopefully PLT_RST_BUF_L is the same.. and no pulse here and nothing on pin 3 of u1950 either

Yes, i disconnected the internal SSD and let it boot from HDD and it still turns off

Originally board hard short on ppbus at C7314. Replaced to remove short. now board without SSD 90% of the time boots and shows no hdd icon. 10% just won't boot. with SSD, sometimes chime with fan spin and dies. tried with external USB bootable. fan spins and dies before apple logo.

There is a pulse there and at VCORE as well.. same dead on SMC bypass

resistace to gnd on L7310/20 is 42ohms only liquid signs on c1801(removed) and Q1840(replaced) and yes stable 3v3_s5/SUS.

Hello, I have an 820-3476 that initially had short on ppvcc_s0_CPU. removed the damaged cap C1008 near the cpu without heat. no more shorts but still does not boot. i detected pulsing voltage when plugin in magsafe from s4 all the way to all_sys_pwgd. no other shorts found so far. any...

Resolve by replacing UB000

Changed U7600 to resolve issue. Thank you for the guidance

Yes some of the s0 power rails are running except for those depending on the 5v rail. Diode mode reading is 0.165 done at L7650

typo there i i have pp3v3_s4 but no pp5v0_s4 even when pin 24 of u7600 is enabled. SMC_ONOFF_L can be triggered when power button is pressed. so seems i'm going past s5 state. i have PM_SLP_s4 and S3. 12v s0 is constant ON @12V, not pulsing.

Hello, I have a 820-4668 not booting, after a few measurements, don't see obvious short or any heating. I have the 1st LED but when pressing power botton has no reaction. my confusion is that in no_boot state i have S5 state power rails(which i do have). but the board is pushing out...

PCH_INTRUDER_L is 2.85V R1451 is good @10K ohm *new findings* i'm measuring 5ohm to ground on PM_BATLOW_L side. Tried injecting 1V into it, for split second, meter went up and went back to zero. i measure again, its now 70+ohm. Now PM_BATLOW_L reads 0.24V i check UB0000 and U2800, i see...

RTC_RESET_L is 3v PCH_SRTCRST_L 3v both 32MHZ and 24MHZ present pp1v0_sus 1V so far this is the only RTH signals listed in the schematic. have i missed any?

With Battery connected, it seems to be charging the battery. getting 300-700mA on charger PM_BATLOW_L is 0 no matter battery is connected or not. and not sure how to do SMC bypass though, tried on another A1708(working fine laptop but once i press and hold the power button it just boots up...