A1278 (820-2936-A) green light no power

[robertpritchard]

hello looking for some help.. i have a green light and everything is good with one wire circut,, PPBUS_G3H is reading 0.12 volt
and is reading 0.00 short to ground. nothing is heating up and laptop was not water damaged whats the best way for me to find this short thanks

[smali]

Re: A1278 (820-2936-A) green light no power

Inject low votage with high current( amp) on short line and observe the PCB short circuit will be heatup.

[ktmmotocross]

Re: A1278 (820-2936-A) green light no power

beware of high current. u can blow component and pads with trace or weld it to another trace under it. start with low current like 1A

[robertpritchard]

Re: A1278 (820-2936-A) green light no power

thanks very much for everyones help .. so i got a new power supply and found my short had to goto 3volt to find it but finnaly Q7630 got hot.. as soon as i took it off short to ground went away after replacing i now get 01.50 on PPBUS_G3H something is pulling it down and cant seem to find it any ideas thanks

[robertpritchard]

Re: A1278 (820-2936-A) green light no power

light stays green when i attach a battery dont know if that might have anything to do with it.. anyone think i should try to reflow the gpu

[dellxps15]

Re: A1278 (820-2936-A) green light no power

reflow gpu is completely no sense.......

u dont have ppbus g3h voltage stable ?

it should be 12.5 volts.

these is generated by u7000 and 2 mosfet near it.

check u7000 voltages and if it get hot as battery light is controlled by it.

[hackintoshmalang]

Re: A1278 (820-2936-A) green light no power

reflow gpu is completely no sense.......

u dont have ppbus g3h voltage stable ?

it should be 12.5 volts.

these is generated by u7000 and 2 mosfet near it.

check u7000 voltages and if it get hot as battery light is controlled by it.

Hi DellXPS15,

i have mbp a1278 (820-2936B), my mbp is missing p5vs3_vo1 on pin 24 (u7200/tps51125)...but p3v3s5_vo2 on pin 7 is present, 5v3v3v_reg_en present on pin 13, pp5v_s5 is also presnt on pin 17.... could it be becaus e bad chip tps51125 for some reason cannot generate p5vs3.. (there are not shot to ground)

Please help me, green light is present, when attach battery change into orange...but no fan spinning ( because missing p5vs3 and pp5vs0)

[dellxps15]

Re: A1278 (820-2936-A) green light no power

bios pin voltages before and after doing smc bypass ?

[piernov]

Re: A1278 (820-2936-A) green light no power

@hackintoshmalang please open another topic for a different issue. Check if PM_SLP_S4_L is present in the meantime.