820-3437-B No PP5V_S5

[lctrbrt]

Hi at all,

I got an Macbook Air (820-3437-B) with liquid damage which wont turn on.

"G3Hot" Rails
PPBUS_G3H = 8,19V
PPBUS_S5_HS_COMPUTING_ISNS = 8,19V
PPBUS_S5_HS_OTHER_ISNS = 8,19V
PPDCIN_G3H = 16,69V
PP3V42_G3H = 3.44V
PPVRTC_G3H = 3.44V

"5V" Rails
PP5V_S5 = 0V


U7701 is in that area where the liquid was and looks some kind of black/burned.

My Questioin is where PP5V_S5 is generated and if U7701 could be the problem which I guess so.

Thanks in advance.

[mon2]

Re: 820-3437-B No PP5V_S5

My Question is where PP5V_S5 is generated

U7501 creates the PP5V_S5 rail.

https://store.rossmanngroup.com/d1-tps51980.html

[lctrbrt]

Re: 820-3437-B No PP5V_S5

Thank you very much.

I changed U7701 and no change but the one that was on the board before was definitly fried; half of the chip is black and the housing disintigrates if I scratch slightly with tweezers on it.

I'll have a look at U7501, hopefully it will resolve the problem.

[piernov]

Re: 820-3437-B No PP5V_S5

PPBUS_G3H = 8,19V
PP5V_S5 = 0V

SMC not running.

[lctrbrt]

Re: 820-3437-B No PP5V_S5

Hi,

thank you very much.

I'm a bit confused about that PPBUS_G3H = 8,19V thing.

I've used the power rail order list and there it states that the PPBUS_G3H should be around 12.6V but on the https://logi.wiki/index.php/PPBus_G3H site it states that the Air's have to be around 8.6V.

So 8.19V should be ok, should'nt it?

Also is there a quick way to check if the SMC is working? Unfortunately I didn't found much info about it not to mention a datasheet.

The SMC itself looks that the liquid didn't arrive it or the surrounding area of it so I think the problem is another with my beginners skills.

Can you recommend some source with a tutorial or something for checking the SMC?

Many thanks!

[mon2]

Re: 820-3437-B No PP5V_S5

Have you replaced U7501 yet? Do you have the PP5V_S5 rail ?

Once you have U7501 replaced / operational - then consider to do a SMC reset:

https://logi.wiki/index.php/Startup_Keys#SMC_Reset:

So 8.19V should be ok, should'nt it?

Yes, till SMC enables as per:

PPBus_G3H is the main power rail of the Mac. It is powered from either the battery or DC in. Its voltage will be based off how many battery cells are in series. The MacBook Pro series uses a 3S2P battery so on the charger it has a PPBus of 12.6V (12.2V before SMC boosts). The Air has a 2S3P battery so on the charger it has a PPBus of 8.6V (8.2 before boosting). This is to charge the battery, which will have a lower voltage than PPBus

[piernov]

Re: 820-3437-B No PP5V_S5

PPBUS_G3H should be 8.56V on MacBook Air starting from 2013 models.
8.2V on PPBUS_G3H and SMC_PM_G2_EN missing mean that SMC is not running.
https://logi.wiki/index.php/SMC_Circuits
You should watch some Louis Rossmann videos.

[piernov]

Re: 820-3437-B No PP5V_S5

Have you replaced U7501 yet?

There is no point in replacing chips randomly without proper troubleshooting procedure — except create more problems.

then consider to do a SMC reset:

SMC reset is effectively performed when disconnecting all source of power (Magsafe and battery).

[lctrbrt]

Re: 820-3437-B No PP5V_S5

Have you replaced U7501 yet? Do you have the PP5V_S5 rail ?

Once you have U7501 replaced / operational - then consider to do a SMC reset:

https://logi.wiki/index.php/Startup_Keys#SMC_Reset:



Yes, till SMC enables as per:

Hey,

no I didn't replace it. The first thing I've learned is like piernov mentioned not to randomly replace parts. The IC looks good and the liquid doesn't came to the area of it so I guess its fine and the problem lies somewhere else.

I took out the board so the SMC should be reseted but no signs of life.

The only thing I replaced was the burned backlight IC but unfortunately no difference in board behavior.

Thank you very much and have a nice weekend

[lctrbrt]

Re: 820-3437-B No PP5V_S5

PPBUS_G3H should be 8.56V on MacBook Air starting from 2013 models.
8.2V on PPBUS_G3H and SMC_PM_G2_EN missing mean that SMC is not running.
https://logi.wiki/index.php/SMC_Circuits
You should watch some Louis Rossmann videos.

I've seen so many videos of him unfortunately I don't do stuff like that often cause our shop is relatively small and mostly we do assemblies so I don't can use the 'learned' stuff regulary and forget it unfortunatley. Also I recognize stuff better which is written down than from videos.

When I try stuff like this I inform the customers that I'm just a beginner and that I can try but that this is mostly for learning and if they want I could send it to a partner which is specalised in boardlevel repairs.

But I'll search for SMC vid's from Louis this weekend and watch them maybe they'll help.

Again, thank you very much and have a nice weekend

[lctrbrt]

Re: 820-3437-B No PP5V_S5

Hi guys

Sry I forgot to post about the results.

Device is working again like a charme. I did like Piernov told and watched some videos from Louis Rossmann and in one he mentioned that the problem also could occur if the connector for programming the board(I think it was J1800) is corroded and it was. After removing it an cleaning the pads the machine started. THe only problem was that after running it for some hours the backlight would went of but there it was just some dirt under the diode arround teh LCD connector.

Again, thank you very much you and this forum are awesome