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[SOLVED]820-2879-B 13" Pro not turning on

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Haralampos

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Hey there and first of all thank you for all the helping videos on your youtube channel.
Actually i am stuck with the logicboard of the topic. it shows green light but does not switch on.

i have 16,5 volts on pin 1 &2, ground on 3&4 and i get 2,85 V on pin 5.

Please help me fixing the board, i would really appreciate.
 
H

Haralampos

New member
Pins of the J6900, the main power plug.it doesnt to seem a liquid damage. No corrosion is visible. Is it possible that it doesnt switch on if the gpu has a bga problem?
 
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dukefawks

Administrator
You have a green light so no use is measuring anything on J6900.

What is the voltage on F7040 and PP3V3_S5(L7220)?
 
H

Haralampos

New member
Both 0 Volt. Thank you so much for your help.

If F7040 has no voltage, does that mean that PPBUS_G3H is down?

F6905 has 16,5 V as well


Update: i measured following voltages on U5010 :

-PP3V3_S5 3,41 Volt
-PP3V42_GH3 3,41 Volt

U7600

-no voltages at all.

U7870 looks really strange, the golden bottom is part gone, i tried to measure PP3V3_S0 (picture in attachement) Wed Jul 20 14-16-42.JPG

Could it be that ISL6259 is damaged?Right behind it i should have PPBUS_G3H at F7040. If i measure at pin 5 CHGR_ICOMP it gives me a small sound like a short.
 
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dukefawks

Administrator
What is the resistance to GND on F7040? Make sure to discharge the bus first by shorting it to GND. No power applied of course!

U7870 is a "no stuff" so is supposed to be missing. I'm suspecting a short to GND on PPBUS_G3H...
 
H

Haralampos

New member
I do get 0.8 as result for resistance with no power and grounded before.

Update :

In diode mode i have a connection between F7040 and GND. shorted?

SMC_BC_ACOK seems to be grounded at U7000, but at U6901 it is not.

Update2 :

As i watched one more video about a problem with PPBus_G3H repair i recognized that my R7010 shows 0,00 Ohm, R7011 shows 9,3 kOhm.
 
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dukefawks

Administrator
Inject voltage with external power supply on F7040. The shorted component will heat up. Apply low voltage first, like 2V and go up till you find the thing getting hot.
 
george-a

george-a

Member
Id remove F7040 and measure both sides for short.. If the side toward the regulator was shorted Id measure the components first without injecting voltage... if the other side toward the rest of the motherboard is shorted then inject voltage there (with F7040 removed so that this voltage goes one direction only)
 
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Haralampos

New member
Ok i unsoldered F7040. When i have the RAM Memory downwards the lower pad(closer to battery connector) of F7040 is not grounded, so not shorted. This pad comes from DC-IN.
The upper pad (leaving the Fuse) with the name PPBUS_G3H is grounded(means shorted?)

I did now the following try with one of my old power adaptor that gives me 3Volt.
I soldered plus on the shorted side of F7040 and - on ground as you can see in the picture.
After plugin of the adaptor i don`t have any more voltage on it.

Where is my mistake?
 

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dukefawks

Administrator
That power supply is probably over current/short protected so it will shut down. Also when connecting anything to a shorted bus the voltage will of course drop close to 0 and current will go to the maximum the power supply can put out. The shorted component should in this case start to heat up.
 
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dukefawks

Administrator
No practical solution without injection a voltage. Make something work to inject a voltage. Tap into the CPU Core voltage from an old motherboard or something. That usually supplies 1-2V at 50+ amps.

Shorts on PPBUS are often one of the bigger black caps.
 
H

Haralampos

New member
Thank you for your response. I ordered a laboratory power supply with 0-30 V and up to 5 amps. After it arrives i will try to figure out the shorted part and let you know.
 
H

Haralampos

New member
Today the ic reached me and was soldered in. Macbook not turning on, but it seems that i am a step further. Battery is charging, F7040 with 12,0 V.
What is the next step? should i measure all Rails now?
 
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