2015 MacBook Retina 12 inch won't power on

[Coronaflyest]

After replacing the screen on this 2015 MacBook Retina 12 inch it no longer turns on. It was running fine before.

I installed the top half of the MacBook on a known working bottom and it works fine, so we can rule out ribion cables, keyboard and everything else on the top half.

If I reconnect battery power and plug it into AC I see the white light on the logic board turn on but it won't turn on.

 

[dukefawks]

Did you disable the battery before replacing the LCD?

 

[Coronaflyest]

Did you disable the battery before replacing the LCD?

Yes I had battery isolation pick on there the entire time I was working on it.

 

[dukefawks]

Uhm, there is a small button to disable the battery.

PPBUS voltage on F7140?

 

[Coronaflyest]

Uhm, there is a small button to disable the battery.

PPBUS voltage on F7140?

I see, I didn't know that. In that case the battery was not disabled I'm not sure if I shorted something out.

Im getting 8.61 volts on PPBUS_G3H off of F7140.

 

[Coronaflyest]

I started measuring the power rails and PP3V3_S5 has a direct short to ground. I also discovered that the power adapter that came with this machine is fake. When I first received the machine I found it very strange that the power adapter looked brand new and the material of the wire was off.

PPBUS_G3H 8.61
PPDCIN_G3H 14.83
PPVRTC_G3H 3.29
PP3V3_S5 0.0
PP5V_S0 0.0
PP5V_S4 0.0

 

[dukefawks]

The short on 3V3_S5 is of course a problem. I assume you are measuring this with the board outside the case with no power connected?

 

[Coronaflyest]

The short on 3V3_S5 is of course a problem. I assume you are measuring this with the board outside the case with no power connected?

Yes with the board is off and out the case.

Any suggestions on where to look to find the short on 3V3_S5?

 

[dukefawks]

Inject voltage and see what heats up. Start low and monitor current.

 

[Coronaflyest]

Inject voltage and see what heats up. Start low and monitor current.

I was hoping that it was a bent pin but they appear to be fine.

I started injecting voltage, at 2 volts I was drawing 1.2 amps, I'm limiting the amps as I go up in voltage but I don't think I should go higher. I saw a video on this same board where Louis finds the short with less than 1 watt of power consumption.

Im currently using 99% alcohol, I might try with freeze spray if I don't find the short tonight.

 

[Coronaflyest]

After injecting voltage for about 10 mins I noticed that the heat sink for the CPU was hot, I was in disbelief. I removed the heat sink and also removed the edge bonding on the top side to check the caps. Sure enough it was the CPU/PCH.

 

[Gurmon]

That is shitty luck.....I hate fixing these machines...

 

[Coronaflyest]

That is shitty luck.....I hate fixing these machines...

Yea man, I would love to know what went wrong since I tested it before taking it apart. I blame the knock off charger, it caught me off guard since it looked legit. I will inspect them from now on before plugging them in.

 

[Gurmon]

I'd put it down to battery still connected or ESD.

 

[G.Beard]

I was hoping that it was a bent pin but they appear to be fine.

I started injecting voltage, at 2 volts I was drawing 1.2 amps, I'm limiting the amps as I go up in voltage but I don't think I should go higher. I saw a video on this same board where Louis finds the short with less than 1 watt of power consumption.

Im currently using 99% alcohol, I might try with freeze spray if I don't find the short tonight.

Of course it's pointless now..... But next time

You should be setting the voltage at a fixed value and going up in current. Set voltage a bit lower than the rail and take the currrent up slowly. Not the other way around.

The amount of current flowing will make the short hot and flow to ground through the path of least resistance (the short) and not bust down any doors it should not. Higher voltage (like pressure) is likely to cause breakdown if it exceeds the rated value of parts and bust through any doors it likes and then you've got a more fucked up board on your hands than you started with.

For all the knowledge and snap attitude to posts on this forum, why is no one else saying this?

Just stick your lip on the board. If you get burned you made some money, buy some cream

 

[Coronaflyest]

Of course it's pointless now..... But next time

You should be setting the voltage at a fixed value and going up in current. Set voltage a bit lower than the rail and take the currrent up slowly. Not the other way around.

The amount of current flowing will make the short hot and flow to ground through the path of least resistance (the short) and not bust down any doors it should not. Higher voltage (like pressure) is likely to cause breakdown if it exceeds the rated value of parts and bust through any doors it likes and then you've got a more fucked up board on your hands than you started with.

For all the knowledge and snap attitude to posts on this forum, why is no one else saying this?

Just stick your lip on the board. If you get burned you made some money, buy some cream

Thanks for the info, I will keep that in mind on the next short.