820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

[Flippers McCoy]

Hello again, everyone!

I have a MacBook Air motherboard, 820-00165-A that won't boot up. The computer spent an hour on the beach, which was plenty enough to fill it up with sand and/or salt. After that, it showed no signs of life, not even a charging light. I removed the motherboard and cleaned out all the salt, which had caused some damage to J6100 and U7090, so I cleaned up U7090 and just removed J6100. After cleaning I get a charging light which switches from green to orange, but it still won't boot. I also ran it through an ultrasonic cleaner, whcih didn't help. I confirmed that U7090 is working, it's properly outputting PP3V42_G3H.
PP5V_S4RS3 and PP3V3_S4SW_SNS are 0V. The other S4 rails are fine, but just these two are 0V. Neither of them are shorted to ground.
I checked on U7501, which creates PP5V_S4RS3 and confirmed that it seems to be working, as U7501 is creating PP3V3_S5_REG_R.
I checked on U8050 and it's getting voltage in, but is not outputting PP3V3_S4SW_SNS. SMC_SENSOR_PWR_EN is 0V, so I suspect that U8050 is not being told to turn on, but I am unsure of that.
I've attached schematics and boardview just in case anybody needs them!

Does anyone have any advice on what to troubleshoot next? I'm at a bit of a dead end from what I know how to do.

Thanks!

[SMDFlea]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

SMC_SENSOR_PWR_EN might be Q5500 shorted or corrosion/smutz

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

I checked it out, It's getting 8.6V from PPBUS_G3H, but not SMC_SENSOR_PWR_EN (as expected) and isn't outputting PBUS_S0_VSENSE. Also SMC_SENSOR_PWR_EN isn't shorted to ground (nothing on Q5500 is shorted to ground either). The area looks really good, I've attached a picture just in case, though!

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

I checked out those forum posts SMDFlea PMd me (PM me if you would like links), looks like I will likely have to try a reflow of the SMC.

• PPBUS_G3H is 8.6V solid
• The traces and probe points near the SPI ROM look great
• R1300 is 3.4V solid
• R1301 is 3.25V solid
• R1302 is 3.2V-3.25V
• R1303 is 3.3V-3.31V
• PM_SLP_S4_L is 0V solid

I'll try reflowing the SMC and see where that gets me

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

The reflow didn't do anything, same symptoms. I don't think I have the tools to do a reball, I've been scraping by with a soldering iron, a heatgun, and tweezers :/

[piernov]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Ok so to recap, all G3H, RTC and S5 rails are ok but there is no PM_SLP_S4_L? Not even pulsing?
Check the RTC clock area, check RTCRST#, SRTCRST#, INTVRMEN#, RSMRST# PWRBTN# that go to the PCH.

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

I forgot what I measured at each one, so I went ahead and measured them all again and this is what I got

PPBUS_G3H: 8.56V-8.57V
PPBUS_S5_HS_COMPUTING_ISNS: 8.56V-8.57V
PPBUS_S5_HS_OTHER_ISNS: 8.56V-8.57V
PPDCIN_G3H_ISOL: 18.91V
PPDCIN_G3H: 18.34V
PP3V42_G3H: 3.40V-3.41V
PPVRTC_G3H: 3.31V-3.32V

PP5V_S5: 4.99V-5.00V
PP5V_S4RS3: 0V

PP3V3_S5: 3.31V-3.32V
PP3V3_S4: 0V

PM_SLP_S4_L: 0V no pulses

RTCRST*: 3.30V-3.31V
SRTCRST*: 3.30V-3.31V
INTVRMEN*: 3.20V-3.21V
RSMRST*: 3.27V-3.29V
PWRBTN*: 3.39V-3.40V

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Bump

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Bumperooni

[SMDFlea]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Have a good look at all the probe points for liquid damage/corrosion. Have a look at J4800 pin 10

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Pin 10 looks a little meh, but it gets continuity between both far ends (the far edge of the pad and the other side of the connector, if that makes sense) and isn't shorted to either of the adjacent pins. Also 18 and 17 look similarly meh, but test fine.
I checked out all the probe points and they all look fantastic, golden and shiny

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Bump

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Bumpitty bump

[piernov]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

No idea, maybe I'm missing something. Any corrosion around the SMC or the PCH? You may try to reflow the SMC, and try to flow some flux under the PCH (if ever the ultrasonic cleaner couldn't clean it all).

[SMDFlea]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Have a good check around the bios chip area.

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

I already tried a reflow on the SMC, and I just examined it and the surrounding area with a microscope and I didn't see anything off at all. I did find some resistors around U5611 that look a little unhappy, but that circuit only becomes relevant in S0 state, so I don't think that's the issue. I've attached a picture anyway, just in case.
I tried reflowing the PCH and adding a pile of flux, and it still has the same behavior except that PPBUS_G3H fluctuates from 20.4V quickly down to 0V then to 20.4V on and on and on.
Same thing with PPDCIN_G3H except it only goes as high as 19.04V

And, surprise surprise, I'm not getting any more S5 rails

[piernov]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Not a great idea to reflow the PCH. However if PPBUS_G3H is now fucked up it should be unrelated. Sounds like bad high-side MOSFET on the PPBUS_G3H regulator or bad PPBUS_G3H controller (the ISL6259).

[SMDFlea]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

flippers, have you put the order in yet for the Quick 861DW

[Flippers McCoy]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

When I put it back on my desk to check out PPBUS_G3H again, it was giving me a steady 8.56V >.>

I checked my power rails again and it's much the same as the last post I made about the state of the power rails, EXCEPT PP3V3_S4 is 3.3V now.
Ah, I didn't know that about the PCH! Why is it a bad idea to reflow?

SMDFlea, there are actually some slightly complicated politics behind the Quick 861DW. Currently I personally don't have the money to buy equipment for myself, nor the time to practice board level repairs as a hobby, as I'm a student working full time. I work in a small computer repair shop full time, and I have been teaching myself how to repair motherboards with the equipment we have on hand as I have the opportunities. Overtime, I have been able to prove myself enough that the owner is comfortable with paying the large amount of money (it's a small shop, we don't have a lot to spare) for the proper equipment. However, I am waiting to hear about another job opportunity this week in the university I hope to attend two years from now.
I would hate for my boss to spend a lot of money on equipment and then have the only employee who knows how to use them leave.
If I do not get the job I am waiting to hear about I will buy the equipment and be much happier for it, if I do get the job I fear that my journey into motherboard repairs may be at an end
Regardless, I should either be getting the proper equipment or stop posting very often in the coming weeks
Thank you for checking up on it!

[SMDFlea]

Re: 820-00165-A Missing PP5V_S4RS3 and PP3V3_S4SW_SNS

Sorry ,no offence meant.If your journey into motherboard repairs does end I`m sure that the skills you`re picking up now will help you at some point in the future.