A1990 Dead, Odd Voltages on USB-C, Nothing on AWAKE's

[thedirekter]

Hey all,

Been lurking for a while to find a solution to my dead A1990 (board # 820-01326-05, I can't find a bv for that one so I've been using 820-01041 for reference) but have come up empty handed. I haven't really done any diagnostics on electronics like this though so I'm sure I've probably missed something. I've soldered and diagnosed keyboards and cars but this is definitely new to me.

My overview thus far:

After browsing the web one night, I closed the lid while it was on the charger, left it on my desk overnight and it was dead in the morning. No response whatsoever from lid opening or power button. No clicks on trackpad, lights on keys or touch bar.
I've tried getting it into DFU, but I've seen a lot of places that the host Mac needs to be on the same OS as my dead one, and seeing as this laptop died over a year ago, I have no idea what OS is on it.
I did check voltage on ports, they're all typically pulling 5v and I've seen anywhere from .002-.011A, usually hovers around .007 though. Odd thing is that sometimes it will pull 20v immediately when plugged in, but no amperage.

As far as testing on the board, here's what I've got:

EDIT: battery voltage is stuck at .48v regardless of how long I leave it on a charger.

PPBUS_G3H: 12.32v
PPDCIN_G3H: 4.99v
PPVBAT_G3H_CHGR_R: 12.36v
PP3V3_G3H_RTC_X: 3.4v
Nothing on PPV1V8_SSD0, PPV2V5_NAND_SSD0, PP5V_G3S, or PP5V_SD.

I also have nothing on any of the PPVDDCPU_AWAKE or PP0V82_SLPDR, and when testing continuity, all of them are grounded on both sides of the caps.
PP1V8_SLPS2R and PPVDDCPUSRAM_AWAKE are okay though.

I'm at quite a loss, I've already accepted this thing probably a very expensive paperweight, but if there's any chance I can revive it that would be awesome.

[mon2]

Remove all power -> remove the USB Type C connector / paddle board. Clean each contact with a Q-tip soaked in IPA (alcohol). The pharmacy grade stuff from Costco is excellent for this. Plan B is to replace the actual board that houses these type C connectors. They should be available from Mobile Sentrix but they usually deal with repair shops only. Alternative, there is Aliexpress. We have seen similar cases and the type C connector was coated with cat puke or at least looked that way when it was brought in for service. Start with this and be sure to clean both sides of the Type C connector blade. Each side is independent and will use either the CC1 or CC2 single contact for communication with the external power adapter. After a proper handshake, the power delivery contract for 20V will be selected.

[thedirekter]

Even with all of the SSD and 5v power, as well as the AWAKE's dead you think just cleaning the ports will do the trick? I checked the ports when I disassembled and they're very clean as it sits.

[mon2]

The power delivery circuit will default to 5 volts out of the external power adapter. Only if the CCx lines are working properly will you have the 20v being selected. A chat initiates between the PD controller on the logic board and the external PD adapter. A list of PD contracts are shared from which the PD controller will select the best choice to power the logic board which will be 20V and some current value (A). Given that once in a while the 20V is selected sounds like the CCx line(s) are not mating well so it is back to the connector as a start. We chased a similar case and it was just the connector at fault. Aside from this start, review the power sequencing of the power rails.

[thedirekter]

So the only issue I see there is that when I get the 20v, there isn't any current being pulled. I'll still pull the connectors just to be safe. I also forgot to mention when I checked the battery voltage (it's been sitting for over a year) it's locked at .48v regardless of how long I leave it on the charger.

[mon2]

See if this helps:

MacBook Pro A1990 Not turning on, drawing 0.00A - 0.02A at 20V repair - Repair Wiki

[thedirekter]

It doesn't power on into DFU either, but I'm not sure if it's because the laptop is actually having power issues, or if the host computer I'm using isn't on the same OS. I have no idea what version OS is on the dead one, but the host is on the latest version OS.

[mon2]

Are you using a known good hardware for the DFU host? We use a 40G rated USB Type C cable to be safe. If the same setup has worked for you in the past then it should be ok here.

Carefully measure the voltage to ground on each pin of the battery connector. The measurements for the SMBUS (I2C) SCL / SDA lines on the battery are of interest. These same lines are used to configure the ISL regulator that creates the PPBUS_G3H. Need to confirm that the SMBUS lines are not stuck low.

If not reviewed already, these are a must read:

A1990 Not starting | Rossmanngroup Forums ; post # 9

CD3215 Bootup Sequence - LogiWiki