Macbook 820-3115B P18V5 issue

[Nuld_]

Hello there,

So i have a A1278 13" (820-3115-B) which was definitely has been worked on.
There is definitely an issue on the "P18V5_DCIN" Line.
Before I´ve connected the Magsafe Connector and something around or on the backside of D6990 was smoking.

D6990 readings:
Pin 1: starts at 5Mohms but is declining
Pin 2: 25,4kohms
Pin 3: 31kohms

[mon2]

Re: Macbook 820-3115B P18V5 issue

Are these the resistance to ground readings for D6990 ?

Remove all power / no battery.

Meter in diode mode.

Check the diodes in the diode mode.

So red meter lead on pin # 1; black meter lead on pin # 3. What is the reading?

Now reverse the meter leads and there should be no flow. Reading ?

===

Red meter lead on pin # 2; black meter lead on pin # 3. What is the reading?

Now reverse the meter leads and there should be no flow. Reading ?

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

Yes, the readings are to ground.
Pin 1-3: 0,227V
Reverse: 0,964V

Pin 2-3: 0,226V
Reverse: O.L

[mon2]

Re: Macbook 820-3115B P18V5 issue

Pin 1-3: 0,227V
Reverse: 0,964V

D6990 is defective and needs to be replaced.

Reverse of 1-3 should be O.L.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

Removed D6990 readings on Board to ground are:

Pin 1: starts at 25Mohms but is declining.
Pin 2: 39,3kohms
Pin 3: 31,25kohms

[mon2]

Re: Macbook 820-3115B P18V5 issue

Resistance readings are fine on the logic board.

Has D6990 been replaced ? Do replace it and measure the DIODE mode readings again. Post the measurements.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

Diode mode readings with new D6990:
Pin 1-3: 0,18V
Reverse: 0,933V

Pin 2-3: 0,2V
Reverse: O.L

So basically the same readings, new D6990 is a know good one.

[mon2]

Re: Macbook 820-3115B P18V5 issue

Measure in the same way, the removed (older) dual diode that was onboard. Measure while it is NOT on your board.

What are the readings ? Something else may be wrong but let us confirm.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

D6990 readings when removed:

Pin 1-3: 0,227V
Reverse: O.L

Pin 2-3: 0,226V
Reverse: O.L

[mon2]

Re: Macbook 820-3115B P18V5 issue

So the diode is good but something may be wrong with the logic board.

Remove F7040 fuse and check the DIODE readings again with the present diode that is onboard. No power during these tests.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

Same readings with F7040 detached.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

Forgot to mention that U7941 is currently missing on this board.

[mon2]

Re: Macbook 820-3115B P18V5 issue

That is ok. Wondering if U6990 is throwing this off.

Do you have a donor board ? Check the readings of the same D6990 on another board.

You can try to remove U6990 and see if the results improve. The question is why this leg of the dual diode is showing this reading in reverse mode but the other leg is ok.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

U6990 Readings:
Pin 1: 1,268MOhms
Pin 2: O.L
Pin 3: 1MOhms
Pin 4: 31kOhms
Pin 5: 0,1Ohms
Pin 6: 31kOhms
Pin 7: 31kOhms
Pin 8: 31kOhms
Pin 9: 31 kOhms
Pin 10: 184,5kOhms

No donor board which i´m trusting that U6990 is okay.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

U6990 seems to be okay

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

But i´m really confused that Pin 3 Ohms doesn´t change even when D6990 isn´t soldered on.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

Anything else I could check for ?

[mon2]

Re: Macbook 820-3115B P18V5 issue

If safe to do so, check of the 3v42 rail is being created by this IC with your magsafe adapter. It is a primary required rail.

If you do not see 3v42, then remove all power and check to see if the output of this IC is being shorted to ground. Check the resistance to ground if the voltage rail is not present.

[Nuld_]

Re: Macbook 820-3115B P18V5 issue

The problem is that D6990 only recieves around 4V at Pin 1 and 2 but R6905 or R6990 are totally fine.

[mon2]

Re: Macbook 820-3115B P18V5 issue

Post the voltage readings on each side of the same resistors and voltage on each pin of this dual diode.