Macbook 820-3115 missing 3V42_G3H

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Greenlight is on with 3,4V on Pin 2 of L6995

That is expected and a good sign. U6990 and linked local parts create this 3v42 rail. This rail is required to turn on the magsafe LED (green / orange). The color of the led is over a single wire communication protocol.

without U7491 even attached.

U7491 is another component that is powered off the 3v42 rail.

Remove all power -> meter in lowest resistance scale -> what is the resistance to ground of PPBUS_G3H ?

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

PPBUS_G3H is at 4,5 Ohms

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

PPBUS_G3H is at 4,5 Ohms

That is too low.

Remove F7040 (fuse) and check which side of the fuse pads is with the low resistance.

Is the short on the producer side (L7030 inductor) or consumer side (pin # 2 of F7040) ?

Do not power up, only remove the fuse to locate the side with the short.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Its Pin 2 of F7040

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Power up without the same fuse and confirm that PPBUS_G3H is present.

What is the voltage on pin #1 of this fuse pad (F7040) ?

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

It starts at 1,3 V but is declining.

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Remove all power. Check the resistance to ground of fuse pad #1. Checking for shorted caps.

What is the resistance?

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Pin 1 is reading O.L

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

What is the meter scale ? OL is a good sign that you do not have any bad caps on this (producer) side.

Confirm the voltage of PPCHGR_DCIN, ACIN, PPDCIN_G3H_CHGR.

If the voltage is powering U7000 and arriving at the high side mosfet, the next step is to confirm the mosfets are OK with resistance checks.

For the mosfet resistance checks, remove all power and check the resistance readings across the mosfet pins (Q7030):

Source (1-2-3) & Drain (5-6-7-8)
Source (1-2-3) & gate (4)
gate (4) & Drain (5-6-7-8)

Post each reading & the scale used on the meter.

Then repeat the measurements for the low side mosfet @ Q7035.

If the mosfet readings are not too low then it is down to U7000 being defective and needs to be replaced.

Without the fuse onboard, the PPBUS_G3H should be text boot perfect on pin # 1 of the (removed) F7040 fuse.

need to grab some groceries..will check back later...

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

PPCHGR_DCIN: 16,55V
CHGR_ACIN: 3,97V
PPDCIN_G3H_CHGR: 16,4V

Q7030:
Souce-Drain: 4Mohms (Mohms)
Source-Gate: 1Ohms (Ohms)
Gate-Drain: 9,5Mohms (Mohms)

Q7035:
Souce-Drain: 4Mohms (Mohms)
Source-Gate: 5kOhms (Ohms)
Gate-Drain: O.L (Mohms)

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

omg, it was hot outside..my milk duds were sweating. should burn the lawn and collect insurance.

Q7030:
Souce-Drain: 4Mohms (Mohms)
Source-Gate: 1Ohms (Ohms)
Gate-Drain: 9,5Mohms (Mohms)

The part is most definitely shorted and needs to be replaced. You can remove it off the board and check these measurements again on the removed component. Unless the ISL is causing this short condition, the mosfet should be replaced.

Q7035:
Souce-Drain: 4Mohms (Mohms)
Source-Gate: 5kOhms (Ohms)
Gate-Drain: O.L (Mohms)

Also consider to replace this part as the resistance is low. Compare the value against a fresh mosfet.

These parts are very inexpensive so consider to buy spares and replace these 2 mosfets and do source also the regulator @ U7000 as a precaution. If you have a donor board, even better.

After the replacements, still leave off the fuse @ F7040 and confirm that PPBUS_G3H is restored.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Q7030:
Souce-Drain: 4Mohms (Mohms)
Source-Gate: 20kOhms (kohms)
Gate-Drain: 9,5Mohms (Mohms)

Q7035:
Souce-Drain: 4Mohms (Mohms)
Source-Gate: 5kOhms (Ohms)
Gate-Drain: O.L (Mohms)

Compered to another Board seems to be okay now.
But Pin 2 of F7040 is still reading around 5 Ohms.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Is the a way to check if U7000 is alright ?

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Compered to another Board seems to be okay now.

The mosfets on this board match the mosfet resistance values of a working and identical logic board?

Is there a way to check if U7000 is alright ?

Yes, when ppbus_g3h is the proper value, u7000 is ok.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

It’s similar to the other defective logic board

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Start with replacing the 2 mosfets. Before replacing, check their resistance while the parts are out of circuit.

PPBUS_G3H (aka F7040, pin # 2) travels all over the board. Respectively, review for any possible damage to the circuit board; liquid damage / corrosion, etc.

If none is found, only then proceed to use a power supply at a low voltage but can use higher current - suggest 0v8 on the voltage and 2-5A on the current. Will link a great video on this subject later today but it is from ADAMIT on how this works.

Summary is that the shorted part will heat up as you inject this voltage. Hoping it is a bad cap downstream. We want to keep the voltage low in case the CPU power mosfets are linked to this rail and if the mosfets are shorted / leaking. A higher voltage will destroy the CPU.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

So I´ve removed both Mosfets and checked them, readings are:

Q7035
Source-Drain: 4,5 Mohms
Source-Gate: O.L
Gate-Drain: O.L

Q7030
Source-Drain: 9 Mohms
Source-Gate: O.L
Gate-Drain: O.L

There is no obvious sign of liquid damage or something else.

Where should I inject voltage?

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Watch this video:

https://www.youtube.com/watch?v=EWuzmIz7hOE

Then with your power supply set to 0v8 (yes < 1v0), current @ 2A-5A should be ok, apply the red power supply lead onto PPBUS_G3H.

Black power supply lead to ground. Check for any part that may be heating up. Hoping it is a capacitor like in the YT video.

Do not increase the voltage - to protect the CPU in case it is shorted to the same rail.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

I´m struggeling with my power supply, I´ve set it to 0,8V but the maximum Current i can inject is about 0,191 A so nothing seems to heat up.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Is there something i´m missing?