MacBook Air A1466 - 820-3437

[duxzero]

Having some issues with PM_SLP_S4_L on this board (hopefully not dead CPU/PCH).

The board had some minor liquid damage the usual places, replaced R5503 and did not find any other visible issues that needed component replacement. The board has now been in ultrasonic wash and looks very clean.

PPBUS_G3H: 8.6v
PP3V42_G3H: 3.42v
PP5V_S5: 5.0v
PP3V3_S5: 3.329v
PP3V3_S4: 0.045v

PM_SLP_SUS_L: 0v (99.6 ohms to gnd)
PM_SLP_S5_L: 0v

PM_SLP_S4_L: 0v

PM_SLP_S3_L: 0v

S4_PWR_EN: 0v

PPVRTC_G3H : 3.329v
RTC_RESET_L: 3.323v
PCH_SRTCRST_L: 3.323v
PCH_INTVRMEN: ~2.6v (can vary between 2.5v-3.2v after each power-on, but stable each time)
PCH_DSWVRMEN: ~2.6v (can vary between 2.5v-3.2v after each power-on, but stable each time)
PCH_INSTRUDER_L: ~2.4v (usually stays 0.2v below PCH_INTVRMEN & PCH_DSWVRMEN values)
PCH_CLK32K_RTCX1: yes, has signal (also replaced U1900 to just exclude chip issues)
PP3V3_S5: 3.324v
PM_DSW_PWRGD: 3.413v
PP3V3_SUS: 0v
PP3V3_SUS_EN: 0v (99.6 ohm)
PM_BATLOW_L: 3.235v
PM_RSMRST_L: 0v

What throws me off other than missing voltages on some lines are the values on PCH_INTVRMEN, PCH_DSWVRMEN and PCH_INSTRUDER_L.

From what I've seen on schematics, the missing signal on PP3V3_SUS is what is needed to eventually power the SPI ROM and then PCH brings up PM_SLP_SUS_L etc..

[reformatt]

Re: MacBook Air A1466 - 820-3437

Use this sequence for troubleshooting:

https://logi.wiki/index.php/G3_to_S3..._and_Broadwell

Not a fan of putting a board in an ultrasonic till it's actually fixed as it washes away all the helpful pointers that you may have missed. I had corrosion under U8005 on one board, which I only spotted because of the smallest tinge of green on the side of it.

PM_SLP_SUS_L is from the PCH, so review the above sequence as to why this is missing. Also check rails etc on initial power up as they can shut down if a problem is detected post S4.

[duxzero]

Re: MacBook Air A1466 - 820-3437

Yeah, I tend to wait putting it in ultrasonic until fanspin, but this one I exhausted all options on and wanted to see if ultrasonic did the final magic.

Thanks for that flowchart, that's convenient. BTW: What does it mean what's written on the flowchart for the PCH_INTVRMEN, PCH_DSWVRMEN and PCH_INSTRUDER_L points that "measures ~3.xv due to probes"? And why would probes only affect measurements here and not on the other points?

[piernov]

Re: MacBook Air A1466 - 820-3437

https://logi.wiki/index.php/User:Pie..._multimeter.3F

[duxzero]

Re: MacBook Air A1466 - 820-3437

Thanks for the link to your faq, I understand, which also explains the other two values due to 330k pull-ups I guess.

I had some progress. So, R5503 was not replaced by me, checked it and it was shorted pads under resistor due to someone using 0402, replaced it now with 0201 from a donor.

Now there is power on some of the ones previously missing:

PM_SLP_SUS_L: 3.324v
PP3V3_SUS: 3.326v
PP3V3_SUS_EN: 3.324v
PM_RSMRST_L: 3.295v
PM_PWRBTN_L: 3.408v

But still missing:

PM_SLP_S5_L: 0v (99.1k ohms to gnd)

PM_SLP_S4_L: 0v (100.4k ohms to gnd)

Added screenshot of clock pulse on U1900 pin 12 taken with a DSO201.

[duxzero]

Re: MacBook Air A1466 - 820-3437

Also PM_SLP_S5_L does in fact pulse for a few ms right after connecting power.

Can this at least rule out dead CPU/PCH, also since PCH actually provides PM_SLP_SUS_L ?

See attached screenshot from DSO201.

[duxzero]

Re: MacBook Air A1466 - 820-3437

So actually all these has one pulse after turning on power:

PM_SLP_S5_L
PM_SLP_S4_L
PM_SLP_S3_L
PM_SLP_S0_L

After the pulse and when signal is low, PM_SLP_S0_L is the only signal that seems a bit dirty low, it has tiny ripples.

Based on this info, is the S0 power rail the place to start looking?

[duxzero]

Re: MacBook Air A1466 - 820-3437

You have a lot of good info on logo.wiki Piernov, I read through your FAQ, and your 820-00165_Pulsing page and did a couple of measurements from info there:

Resistance between pins on U7100

17/18 = 3.2 ohm
27/28 = 19.8 ohm

So this seems OK.

Then I read the Bootup_Signal_Order flow chart, did most measurements there (checking for pulse) and this is the results for the signals marked in green on the chart.

P1V8S3_PGOOD: 3.28V (one pulse)
DDRREG_PGOOD: 3.28V (one pulse)
P5VS4RS3_PGOOD: 3.28V (one pulse)

P1V05S0_PGOOD: 1.04V (one pulse)
S0PGD_C: 2.64V (frist one pulse, then stays high)
VMON_Q2_BASE : ~680mV (one pulse)
VMON_Q3_BASE : ~680mV (one pulse)
VMON_Q3_BASE : ~760mV (one pulse)

ALL_SYS_PWRGD: 0V no pulse

So it seems some of the pulses (VMON_Qx) from Q8150 are very low, and the high signal on S0PGD_C seems odd (would think it should be ~3.3V). So I think that I'll try replacing Q8150 and checking resistors and caps around it.

Edit: I checked the VMON_Qx signals in FlexBV against OBDPath data for this board, and seems these voltages are actually close to what's listed there. The only exception being S0PGD_C which is listed as 120mV in the database. R8156 resistor has correct value at ~150K ohm.

[duxzero]

Re: MacBook Air A1466 - 820-3437

After replacing Q8150, in addition to values in post above, there are now also:

ALL_SYS_PWRGD: 3.28V (one pulse)

I also checked U1930 which ALL_SYS_PWRGD goes into:

CPU_VCCST_PWRGD: ~1.00V (one pulse)

Then some of rest on S0 state flow chart

PCH_HSIO_PWR_EN: 3.36V (one pulse)
|
PP1V05_S0SW_PCH_HSIO: 1.04V (one pulse)
|
PP1V05_S0SW_PCH_VCCSATA3PLL: 1.04V (one pulse)
PP1V05_S0SW_PCH_VCCUSB3PLL: 1.04V (one pulse)

...and this is where I'm now stuck at.

Edit: I can also add that I've read the SPI ROM through the J6100 connector 3 times and verified the checksum, and also flashed a clean ROM from a working board to exclude data corruption.

[duxzero]

Re: MacBook Air A1466 - 820-3437

Replaced U1950

Probed U1950

->ALL_SYS_PWRGD: 3.28V (one pulse)
->CPUVR_PGOOD_R: 3.28V (one pulse)
<-PM_S0_PGOOD: 3.44V (one pulse)
->SMC_DELAYED_PWRGD: 0V
<-SYS_PWR_OK: 0V
—
<-PM_PCH_SYS_PWROK: 0V

I'm not sure when SMC_DELAYED_PWRGD is supposed to go high, but this signal is needed to create SYS_PWR_OK and PM_PCH_SYS_PWROK. Is the problem missing SMC_DELAYED_PWRGD or does this come later and is irrelevant due to the other signals just pulsing briefly once? It's probably the latter due to signal being named "DELAYED", but nice to get it confirmed.

[reformatt]

Re: MacBook Air A1466 - 820-3437

So the board has previous rework? If that's the case, look over the board very carefully, review what has been touched and ensure they've actually placed the right components in the right spots.

I've had boards where there was liquid damage, and the last repairer introduced problems on top of the existing fault. In one case, orig fault was an open circuit inner layer track for PP3V3_SUS, but he went and screwed with the RAM strapping for some unknown reason. So I rarely trust anyone elses work until I review it.

Pay also close attention to the balls under the SMC. It sometimes pays to remove the corner bonding and reflow it with flux. I fixed a 165 board last night that wouldn't POST past EFI load with a SMC reflow. It's used in many parts of the power and post EFI boot sequence so helps to eliminate it. It often gets crap under there after liquid spillage, and as the board has been washed, it's hard to tell. Ultrasonic won't resolve any issues under that so reflow is the way to go.

[duxzero]

Re: MacBook Air A1466 - 820-3437

Yes, had previous work done on it. I'm the one that did the ultrasonic wash though, so I did check everything carefully first.

The resistor I mentioned was basically the only component replacement I could see in addition to some scraping around the same areas. Also seemed the board had been "washed" in some weird way, maybe a brush and isopropyl alc.

I've already reflowed the SMC, so I'm thinking perhaps replacing it, have a donor board and the stencil for it and have done reballing with paste on a couple of these before with success, but I'll go over all rails again first.

Thanks for the input though.

In your case, the dude that screwed with the RAM strapping maybe thought he would increase his RAM size by just changing the strapping.

[duxzero]

Re: MacBook Air A1466 - 820-3437

I guess I could have saved myself some trouble checking resistance to ground on PPVCC_S0_CPU a bit before which is 0 ohm to ground.

Removed R7310 and R7320, still 0 ohm to ground, then injected ~0.9V into PPVCC_S0_CPU and it draws ~3.05A while none of the surrounding connected caps getting hot. I soaked them all (both sides of the board) in isopropyl alc to look for any fast evaporation. The CPU die does not get hot either, but guess it does not have to either since it's not really on and the short can be anywhere incl. BGA balls under.

Well, on the bright side I got myself a new 820-3437 donor board without holes drilled through it.