Macbook 820-3115 missing 3V42_G3H

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

How much current can your power supply support ?

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

It supports up to 10A, I guess the problem is that I'm using C.V mode at 0,8v and only limiting the current up to 2-5 A, but the resistance is at 4,5 ohms. So it generates only a current around 0,19A.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Or am I missing something?

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Are the mosfets supposed to be soldered back on in order to inject the voltage?

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

hi. no, leave the mosfets off. only interested now to resolve the short that is on the consumer side (downstream) that is connecting to fuse F7040, pin # 2.

Consider the following process:

1) leave F7040 off. confirm that F7040, pin #2 has a low resistance to ground.

2) see attached for the fanout of the PPBUS_G3H power rail for this logic board.

3) Remove the backlight as the guilty party by reviewing the fuse on PPBUS_S0_LCDBKLT (F9700). Suggest that you remove but solder one leg on the pad so that you do not lose the fuse - just our method. Just be careful the fuse does not short against any other part or trace.

Now check the resistance to ground of PPBUS_G3H - still low ? Continue...

4) Remove all power. Inspect the mosfet linked to the CPU power rail @ Q7630. This is a DUAL mosfet inside a single package.

Meter in resistance mode.

Check the resistance across the mosfet legs of:

2 & 7
1 & 7
1 & 2

and the other internal mosfet

7 & 3,4,5 (pick any pin since they are shared)
7 & 6
6 & 3,4,5

Record each resistance reading and post them here along with the scale used on your meter.

If the resistance is a low value, the mosfet could be defective.

We want to be sure the mosfet is not leaky for the CPU so that we can proceed to adjust the injection voltage and/or current settings.

Repeat the same testing for Q7100.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

1) Yep still low
3) Low aswell
4)
Q7630:

2 & 7: 5,1 Ohms (Ohms)
1 & 7: O.L (MOhms)
1 & 2: 98,9kOhms (kOhms)

7 & 3,4,5: 0,4Ohms (Ohms)
7 & 6: 5,92MOhms (MOhms)
6 & 3,4,5 5,92Mohms (MOhms)

Q7100:

2 & 7: 19,8 Ohms (Ohms)
1 & 7: 97,6kOhms (kOhms)
1 & 2: 97,6kOhms (kOhms)

7 & 3,4,5: O.L (MOhms)
7 & 6: O.L (MOhms)
6 & 3,4,5 33,7Mohms (MOhms)

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Both of these mosfets have low resistance readings.

What is the resistance to ground of L7630, pin # 2 ?

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Pin 2 of L7630 reads about 0,5Ohms

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Is there something else I should check for ?

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

See attached.

PPBUS_G3H powers many rails including PPVIN_S0_VCCSAS0.

The mosfets for each regulator must be working properly to regulate the local rail.

Based on the earlier post, Q7100 - pins 2 & 7 have a very low resistance. Can you confirm it is 19R8 (19.8 ohms) ??

This implies that the voltage from PPBUS_G3H (~12 volts) is likely to have travelled onto the PPVIN_S0_VCCSAS0 rail = CPU voltage. This will have harmed the CPU.

Remove Q7100 and check the resistance out of circuit of this dual mosfet. Make a note of the pin # 1 orientation before removal.

After Q7100 is removed, check the resistance to ground again of PPVIN_S0_VCCSAS0 (L7100, pin # 2). Is it still very low ?

Likely the CPU is dead but wait on the above details and others to comment.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

It´s 22,3 Ohms on Pin2-Pin7.
Yup Pin 2 of L7100 is still at 5,8 Ohms after removing Q7100

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Pin 2 of L7630 reads about 0,5Ohms

What is the resistance to ground of L7630, pin # 2 now that Q7100 has been removed ?

The resistance showing now may be ok for the CPU rail.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

L7100 is reading 17,12 Ohms now.
L7630 reads 0,5 Ohms on Pin 2.

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Review the resistance on mosfet Q7630 in the same manner as Q7100. Post the readings.

Then remove Q7630 and check the resistance to ground of L7630, pin # 2.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Q7630:

2 & 7: 5,1 Ohms (Ohms)
1 & 7: 1,3 Mohms (MOhms)
1 & 2: 95,2kOhms (kOhms)

7 & 3,4,5: 0,5Ohms (Ohms)
7 & 6: 35,2MOhms (MOhms)
6 & 3,4,5 35,5Mohms (MOhms)

Pin 2 of L7630 is at 1,6 Ohms after removing Q7630

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Anything else i should look for?

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

What are the resistance check values of Q7630 with Q7630 removed off the logic board ?

The readings are very low again and Q7630 appears to be defective.

Concern again is that with a defective mosfet, the mosfet is just leaking the high side high voltage present on pin # 2 and flushing it to the downstream load = CPU. The CPU cannot handle PPBUS_G3H as the raw voltage.

A possible savior is that the LOW side mosfet is also very low so perhaps the high side and low side mosfets fought it out and the CPU is still safe but we do not yet know.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

Q7630:

2 & 7: OL (MOhms)
1 & 7: O.L (MOhms)
1 & 2: O.L (MOhms)

7 & 3,4,5: 640 Ohms (kOhms)
7 & 6: O.L (MOhms)
6 & 3,4,5 O.L (MOhms)

Q7630 seems to be okay.

[mon2]

Re: Macbook 820-3115 missing 3V42_G3H

Review the resistance to ground readings of U7600. Someone is causing the resistance readings to be very low.

[Nuld_]

Re: Macbook 820-3115 missing 3V42_G3H

U7600 reading:

1: 0,1 Ohms
2: 1,45kOhms
3: 84,3kOhms
4: O.L
5: 0,1Ohms
6: 1,435kOhms
7: 3,1kOhms
8: 3,1kOhms
9: 10kOhms
10: 0,7Ohms
11: 98kOhms
12: O.L
13: 17,3kOhms
14: 17,3kOhms
15: 6,2MOhms
16: 0,1Ohms