MBP A1278 - Won't power on, no green light on charger, but dim blinking orange light.

[TexpertLLC]

MBP A1278 - Won't power on, only green light on charger, but dim blinking orange light. Minor liquid exposure and some corrosion noticed in the area just to the right of the battery connector on board. Is this worth attempting repair? Should we do testing to pinpoint what components need to be replaced? Thanks for any help.

 

[dukefawks]

pp3v42 present? I bet the cap under that sponge is shorted and shorting out 3v42 rail.

 

[TexpertLLC]

Hey Duke I have watched most of Louis' videos and searched elsewhere as well. I try not to ask about the elementary stuff, but could you point me in the right direction to learn the best way to check for pp3v42 and other power rails? This is a 820-3115 and I have checked at C7040 and gotten .9, .843 with the voltage slowly dissipating. I have tried one different DC-in jack but that seems to make no change. Earlier today I got a solid green light on that stayed on, but I can't seem to get that again, since then i have gotten a green light for like a second another time, but now its back to no green light at all. I have not replaced any components yet but 3 or 4 of the surrounding caps do not beep out. I did remove the sponge you mentioned covering a shorted cap. it doesn't show any signs of additional damage. Any help is appreciated. If I am asking too much and you think I should do the one on one training just tell me, but I would like to learn as much as I can without having to travel to NYC. Thanks again.

 

[TexpertLLC]

Hey Duke and or others, just a reminder I still need some guidance on this repair. Thank you

 

[dukefawks]

Reply to a post don't "comment" or I won't see it.

Look up 3V42 bus on schematic and measure it. PP3V42_G3H

 

[TexpertLLC]

Please forgive me if I'm still not doing this right. I measured pin 4 and then pin 7 of U6990 and i'm getting 9.87 each time. Also I just noticed there is very faint clicking sound when the ac adapter is connected.

 

[dukefawks]

I have no idea which board you are working on so I'm gonna assume 3115.

Look at schematic and tell me what pins 4 and 7 are connected to. I want to know the voltage on the PP3V42 rails.

 

[TexpertLLC]

Hope this attached pic shows what you are looking for and yep this is a 3115.

 

[jgraffis]

What voltage do you have on the PP3V42 rail?

 

[TexpertLLC]

I am confused as to where exactly I am supposed to take the measurement at? In other words at what component should I measure with the probes?

 

[aprendiz]

black probe on GND and red probe on L6995, dont forget to turn on the DMM (Digital multimeter).....................

 

[TexpertLLC]

LOL ikr, sorry Im such a newb, you would think after a year of watching Louis I would know this stuff, but I cannot find a single video where he shows exactly where to take your measurements. I really appreciate the help. Okay there is no reading on either side of L6995, and yeah the DMM is definitely on.

 

[dukefawks]

Resistance to GND on L6995?

 

[TexpertLLC]

Resistance to GND on L6995 measures

PIN 1: 1.3 no charger, 1.5 to 1.6 with charger

PIN 2: .8 with no charger, .7 with charger.

Again sorry if that I'm not measuring it right, brand new to troubleshooting board repair. On a positive note I am pretty good at soldering once I figure out what needs replacing.

 

[dukefawks]

1.3 what, Ohm, KOhm, MOhm? Also NEVER measure anything with power applied unless measuring voltage.

 

[TexpertLLC]

1.3 Ohm. oops, noted on the no power

 

[TexpertLLC]

Where can i find this "sticky" on backlight repair?

 

[jgraffis]

it is on the top of the forum page there are 3-4 post in different colors. one says something about backlight

 

[dukefawks]

Looks like your PP3V42 bus is shorted to GND. Pretty sure the shorted cap will be under the sponge next to the BIL connector. Inject voltage on 3V42 bus and see if anything heats up in that area.