MacBook - 2021 A2485 - 16 inch - 820-02100-A - No Boot / No Power

[applejuice95]

Hi there, currently working on 820-02100-A logic board - No boot Chime, no Power on. - Very Minor Liquid Exposure - All cleaned with IPA , did a partial ultrasonic as well . Clean and dry.

MagSafe - Orange light cycles off then back on every 5-7 seconds
USB-C Ports - All 3 get to 19.9V/20V - .5A then Cycle ever 5 seconds.

All 4 CD3218 Chips have been checked at their LCD-CORE 3V5 and 1V5 lines at the local Capacitor, all are getting 1.5 and 3.5V But each have a different Voltage drop when the board cycles.. See below

(PP1V5_UPC_LDO_CORE) - AT EACH CD321

U5500 - Drops from 1.5V to 0.7V (for just a second when the board cycles)

UF400 - Drops from 1.5V to 0.0V (for just a second when the board cycles)

UF500 - Drops from 1.5V to 1.3V (for just a second when the board cycles)

UG400 - Drops from 1.5V to 0.0V (for just a second when the board cycles)


U5500 - PP3V3_SW_ACE5 - 3.16V problem?

UF400/UF500/UG400 - PP3V3_S2 - 3.16V problem?

PPBUS_AON - 12.6V
PP3V3_AON - 3.3V
PP3V3_S2 - 3.3V
PP5V_S2_MAIN - 5.1V
PP3V8_AON - 3.8V
PP1V8_AON - 1.8V

No shorts detected on any Power rails. Unless I'm missing one. Unfortunately this is such a new board, so many new rails are present to get a boot.

NO ITS NOT IN DFU! LOL

Please Help!

[mon2]

https://boards.rossmanngroup.com/thr...display.65127/

[applejuice95]

https://boards.rossmanngroup.com/thr...display.65127/

Brother, the machine in this Rossman thread actually boots and gets trackpad feedback..

On MY machine, I have no fanspin, no boot, nothing.

Can you tell me what you're trying to infer here?

[mon2]

Review U5660.

Is the PP3V3_UPC5_LDO stable directly on the SPI flash? Also PP3V3_UPC0_LDO on UF260 stable?

Review each resistor in the path from this flash to the PD controllers. Having 20v is a good start but perhaps the firmware is corrupt and causing this power cycling.

U5500 - PP3V3_SW_ACE5 - 3.16V problem?

UF400/UF500/UG400 - PP3V3_S2 - 3.16V problem?

To me, yes. What is the exact resistance to ground on each rail? This should be ~3v3.

Update:

Do you have a thermal camera? Review the device @ U5310. Also test the diode @ D5311.

Confirm the input voltage is stable for PPVBUS_USBC5. Respectively, the enable pin for this low current LDO should be as well for HVLDO_EN.

Finally, the output should be stable but the part is from TI so is a suspect by vendor name. This part may be defective as the power delivery controllers appear to be working since they are negotiating the 20V PD contract.

[applejuice95]

PP3V3_UPC0_LDO on UF260 - 3.16V as well.. It drops to .5-7V when the board cycles just like the other LDO rails

Res to Ground for PP3V3_SW_ACE5 measured at C5500 is around 22 K-Ohms
Res to Ground for PP3V3_S2 measured at CF400 , CF500, and CG400 is around 22 K-Ohms

I'm new to this, sorry. Not sure what SPI Flash is. I see some SPI related Lines going into UF260- If this is what you're asking about. They're also 3.12V-3.16V , and cycle down to .5V just like the other 3V3 spots..

Every 5V rail gets 5.1

[applejuice95]

Yes we have thermal cam and the power supply from NorthRidge.

U5310 Looks clean.


Pin 5 of U5310 - HVLDO_EN - .075V then drop to 0.00V when the board cycles.

D5311 is .5V on Pin 1 (Left side) and 3.16 on Pin 2 (left side)
D5311 - Diode Mode across the chip is .113V (no power plugged into the board)
Res to ground of Pin 1 is 110 Kohms - and Pin 2 is 22 Kohms

Measuring PPVBUS_USBC5. at D5401 - Pin 2 is 0.00V and Pin 1 is .78-.81 similar to Pin 5 of U5310

[mon2]

What is the exact resistance to ground of PP3V3_UPC0_LDO? This low current LDO rail is created by UF400. If there is a higher than normal load on this rail, there will be a voltage drop as you are observing.

Res to Ground for PP3V3_SW_ACE5 measured at C5500 is around 22 K-Ohms
Res to Ground for PP3V3_S2 measured at CF400 , CF500, and CG400 is around 22 K-Ohms

These lines are not showing a short condition with the high resistance.

SPI flash is the memory storage device that holds the firmware for the master device. In your case, the PD (power delivery) controllers are the CD321x devices and the firmware is stored externally onto the SPI flash devices. Sometimes, when the 20V power delivery contract cannot be negotiated, the fault is with corrupt firmware inside the SPI flash device. They are called SPI flash because they use the SPI line interconnect. Some use QSPI (quad SPI flash lines); I2C / Microwire. There are similar ram devices with less and less number of interconnect lines including HyperRam. Embedded processors / FPGA devices are able to use HyperRam with fewer lines yet maintain the expected low latency for the reading / writing to the device.

[applejuice95]

Thanks for explaining this, and for all your help with this. If the Flash is external from my 4 PDs , what component(s) is/are these on the board?

[mon2]

Devices are:

UF260
UF360

[applejuice95]

REVISE*** -

Just to inform you, all of the above tests and voltages are while board is on bench plugged in via USB-C

Just pulled the DC-IN jack for the MagSafe and connected it to the board

So with board on bench with Magsafe on it, (which again cycles between orange light and turning off)

D5401 gets 5 volts on that USB5 Rail, I'm assuming it was supposed to be .08 like before if its plugged into power via USB-C

D5311 still is at 3.16V on Pin 2 just as with the USB-C method of power to the board, and drops to 0.00 every cycle However, Pin 1 does get 3.37V for just a second then drops to .117V and repeats this.

[applejuice95]

I'm not sure why I sad PP3V3_S2 - 3.3V in the original post. Its definitely 3.16V

[mon2]

Pin 5 of U5310 - HVLDO_EN - .075V then drop to 0.00V when the board cycles.

Something is wrong here. With these voltages, the LDO is not being enabled.

Is the voltage of PPVBUS_USBC5 stable? Check each and every component that are linked to this enable pin. When you have the IN voltage, the EN pin should also be a logic '1' = high to enable this LDO.

See attached.

[applejuice95]

Measuring at C5310 for PPVBUS_USBC5

Powering the board with USB-C Charger (At ALL 3 locations)
- .08V - 0.00V cycling

Powering the board with MagSafe 3 @ J5401
- 20V then drops to 5V cycling back

[applejuice95]

UPDATE

thermal reveals R5908 lights up for a second then L5800 glows hot consistently

[mon2]

What is the exact resistance to ground of PP3V8_AON? No power to the board during this test.

[mon2]

It appears from post #13 that you have an issue with one or more of the PD controllers. At the very least, when you mate a working USB-C PD adapter to the board, the CD321x should output the power up default of 5v. This voltage should reach the IN pin on U5310 and also the local network of parts should enable this LDO using the EN pin #5. Yet, these rails remain at ~0v so there is a power path fault in this case study.

The MAGSAFE 3 leg appears to be working but drops to 5v and then power cycles.

If you use the MAGSAFE 3 adapter, what voltage do you see on the EN pin #5 of U5310? Does this pin ever go to a logic '1'?

[applejuice95]

PP3V8_AON measuring resistance to ground -

Very different readings depending on what part of the board Im measuring at on this same rail

CR707 - 2.5K ohms
CR737 - 6K ohms
C5892 - 5K ohms
C5891 - 15K ohms
CR667 - 0.2 Ohms
CR637 - 0.7 Ohms
CR607 - 0.6 Ohms

[mon2]

CR667 - 0.2 Ohms
CR637 - 0.7 Ohms
CR607 - 0.6 Ohms

These are too low and are show stoppers.

The same resistance should appear on each point under test since they are linked to the same power rail of PP3V8_AON.

Try this, remove all power. Meter in the lowest resistance mode.

One meter probe at CR667; other meter probe at CR707. What is the exact resistance in ohms? It should be ~0 ohms since they are both on the same power rail.

[applejuice95]

Pin 5 on U5310 when on Mag power is at 4.7V then drops when it cycles.

[applejuice95]

These are too low and are show stoppers.

The same resistance should appear on each point under test since they are linked to the same power rail of PP3V8_AON.

Try this, remove all power. Meter in the lowest resistance mode.

One meter probe at CR667; other meter probe at CR707. What is the exact resistance in ohms? It should be ~0 ohms since they are both on the same power rail.

Unfortunately my FLUKE 101 only does auto ranging for resistance.

However. CR667 and its 2 other Caps below it are all at that 0.8 Ohms

CR707 and its buddies beneath are all at 2.5K ohms