A2992 - 5V - 0.00A - No Power

[applejuice95]

820-02918 - 2023 M3 A2992
- 5V 0.00A on Meter - USB-C
- No light on MagSafe

Small corrosion on UR730, and CR765 - Cleaned and scrubbed with ISP

Re-assembled. Tested, and computer worked, battery charged. Today after replacing a new USB-C I/o board, the machine no longer works.. We realized this was the wrong part, it was a port for A2442/A2485. The M3 uses a new part 821-04548-A.

After this, now computer has no power.


-PPBUs_AON = 0.00V
-PP3v8 = 0.00V
- PPDCIN_AON (F5600) - 5V


No DFU mode.

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of PPBUS_AON. What is the exact resistance?

[applejuice95]

Measuring at C5253 & C5254 - 135ohms same thing near C9803

[mon2]

Connect the power adapter. Carefully measure the voltage to ground of:

PPCHGR_VDDA
PPCHGR_VDDP

SMBUS_BATT_SCL
SMBUS_BATT_SDA

[applejuice95]

PPCHGR_VDDA - 4.46 V
PPCHGR_VDDP - 4.416 V

SMBUS_BATT_SCL - 0.0V
SMBUS_BATT_SDA - 0.0V

(board is out of machine, on bench)

[mon2]

Remove all power. Measure the resistance to ground of PP1V8_S2. What is the resistance?

PP1V8_S2 is the LDO output created by the UF400 PD controller.

[applejuice95]

1.4Kohm

[mon2]

No short here.

With no power to the board what is the resistance to ground of PP3V8_AON?

Not sure on which PD controller is active for the port under use.

Test if you have a voltage output at:

PP3V3_UPC1_LDO (UF500)
PP1V8_UPC1_LDO (UF500)
PP1V5_UPC1_LDO_CORE (UF500)

PP3V3_UPC0_LDO (UF400)
PP1V8_UPC0_LDO (UF400)
PP1V5_UPC0_LDO_CORE (UF400)

For the active USB-C port, the local PD controller linked to that USB-C connector will offer the above LDO rails otherwise something is wrong.

Based on the earlier posts, you are missing the 1v8 rail required for the I2C communication with the buck / boost regulator for PPBUS_AON.

[applejuice95]

Thanks Mon, checking on Monday. we are closing out for the weekend. Thank you for all of your help, talk later.

[applejuice95]

PP3V8_AON - Resistance to Ground = 400ohms (starts around 100, builds up, stabilizes at 400).

(With Power cable in USB-C port #2) These are the voltages for UF500

PP3V3_UPC1_LDO (UF500) - 3.23V
PP1V8_UPC1_LDO (UF500) - 0.00V
PP1V5_UPC1_LDO_CORE (UF500) - 1.5V

Yes it would seem 1.8V rail is absent. 1.8V rail is also absent when power is moved to USB-C port #1 (just right of the MagSafe) - 3.3V is present on UF400, but 1.8V is not.

Checking for resistance to ground with power removed,
PP1v8_AON on C2221 - 23kOhms
PP1V8_S2 - 14kOhms
PP1V8_AWAKE - 4kOhms

[mon2]

Test for the PP1V5_UPCx_LDO_CORE rails on each PD controllers which feeds the BMC interface used by the CCx lines to select the 20v.

[applejuice95]

- The 3 USB-C PDs
PP1V5_UPC0_LDO_CORE - 1.5V
PP1V5_UPC1_LDO_CORE - 1.5V
PP1V5_UPC2_LDO_CORE - 1.5V

- The MagSafe
PP1V5_UPC5_LDO_CORE - 1.5V

[applejuice95]

Have any more ideas?

I can't help but feel like this was caused by installing the wrong USB-C i/o board.

Mobile Sentrix sells them, but they're selling A2442/A2485 i/o boards as being compatible with A2992/A2991 M3 models which it is not.. Different part number entirely.

Originally client had a no response machine. We inspected the usb-c port that works with PP1V5_UPC2_LDO_CORE .. It was all burned up. Removed it, and reinstalled board with this one i/o board removed from the equation. There was a tiny amount of corrosion near U730 we cleaned, but the machine booted fine. It worked, charged the battery to 100%.. The next day after ordering what we thought was the correct replacement for the burned up i/o ubs-c.. On the first try, only metered at 5V 0.00Amps.. Has been this way ever since. Hard to not draw this conclusions that it was the improper equipment which caused this problem.

I only can hope it is not U8100

[mon2]

Suggest to order the relatively new Qianli iBridge A3 Tester to allow you to quickly confirm the state of the USB-C ports. Also acts like a USB-C meter, etc.

https://www.mobilesentrix.com/ibridg...-tester-qianli

Not sure about the compatibility across the USB-C paddle boards at this time. What are the markings (silk screen) on the A2992 paddle board? I do have a good contact at Mobile Sentrix (Canada) and can alert him if there are errors on their website. It is important to have the proper connector onboard.

[applejuice95]

Heres the item: https://www.mobilesentrix.com/usb-c-...2485-late-2021

Says compatible with M3 14" & 16"

I do not believe this to be true. The part number for the M1 Pros is indeed 820-03084-02/ 923-10062 and this is indeed what they're selling.

For A2991/A2992 M3 models. the part number is 821-04548-A (or 821-04548-01)

Similar to how the A1707 ports were different from A1990 even thought the connector was the same.

I believe installing this part, and plugging up power may have shorted this 1.8V rail. Which I'm still puzzled on.

I read through the only other similar article on here, where you had helped a gentleman with an M2 A2338 with a similar short. 5V 0Amps, missing 1.8 rail.. Kind of left it in the wind but looked like U8100 was shorted. Which I REALLY hope isn't the case here.

They said they've forwarded to Moosa for review. I also sent them some photos of the 24" iMac displays they're selling as compatible for M3 an M1 models which is also not true. The daughter board and camera/ALS sensors were totally different sizes even thought the LCD is the same. Doesnt work lol

[mon2]

Very interesting review. Also have alerted the team in Canada on this thread.

At this time, do you have the proper USB-C paddle board for your unit? Any luck with a DFU with the proper paddle board?

[applejuice95]

Waiting for one coming off of eBay then going to re-run it.

You think its possible with that rail being absent that DFU revive can still be a possibility?

[mon2]

We have an imac in from repair (for a while now) that is in a similar position. From other cases that are public, most likely to be tossed into the landfill but we are stubborn and have countless hours into the attempted repair. With feedback from Master Liu, he suggested that the T2 firmware is corrupt. We too do not have the 1v8 rail on this imac which is created by a local PMU. He noted that a corrupt T2 firmware can cause this issue. To us, it is a catch-22, from what we know, you need the 1v8 to perform the DFU but curious to know of your position. He also mentioned that it is ok to take the T2 firmware off another board to place onto ours and then continue to test with the Apple configurator to restore the unit. The parts are extremely small and the board is very crowded. Will try these ideas this week.

Find it strange that BOTH pd controllers are missing their 1v8 rail. For this reason, the Qianli iBridge A3 tester may offer some help on your case. Test if the 1v8 is present on other units you may have with this PD controller. As far as I can see, this 1v8 rail should should enable upon power up since it is only a low current LDO. Assuming the LDO is burnt out, then the pd controllers would have to be replaced but the resistance to ground show they are not shorted.

[applejuice95]

What if, we set up the unit for a DFU revive and while running through the process -- we inject 1.8V into the 1.8 rail.. Just give her what shes missing.

If its incapable of sending 1.8V through the rail potentially due to a firmware corruption, but the only way to fix the corruption is a DFU. Supplement the voltage with an artificial V-IN? Anyone ever done this?

This is one of those, "sounds good on paper" ideas but, hey who knows.