820-02098 - a2442 - power cycling

[Opunktvoll]

Hi all,

I have a a2442 with liquid damage mainly at Q5800 and UF800 area. But nothing serious. Also corrosion and burn marks at both USB-C ports (the ones below the magsafe connector). I cleaned all up and replaced the bad USB-C ports.

Ampmeter shows 20V and 0,13A for around 10 seconds and then the Ampmeter reboots. Same behavior on every port.

When reassembled in housing the display lights up and shows battery warning sign, so at least it´s doing something. But only for 10 seconds..


Any idea where to look at? First suspect was CD32.. because of the burn marks and constant power cycling, but they should be fine because of 20V is present.


I appreciate any hints or support

[mon2]

Re: 820-02098 - a2442 - power cycling

This may be one of those models where a battery is requied to boot.

Suggest to test with a known good battery attached to the board.

20V confirms your CD321x ACE controllers are ok.

[Opunktvoll]

Re: 820-02098 - a2442 - power cycling

Doesn´t make any difference with battery installed. Still cycling every 10s and still showing battery warning sign.

Battery is fully funktional and also charging when connected.

[mon2]

Re: 820-02098 - a2442 - power cycling

Measure the voltage to ground of each pin on the battery connector. Interested in the voltage level of the SCL and SDA pins which will be used to communicate with the battery's BMS module.

[Opunktvoll]

Re: 820-02098 - a2442 - power cycling

SYS_DETECT_L: 0.45V
SMBUS_BATT_SCL: 0.5V
SMBUS_BATT_SDA: 0.5V
TP_BMON_IOUT: OL

Measured with red probe on ground.

[mon2]

Re: 820-02098 - a2442 - power cycling

SMBUS_BATT_SCL: 0.5V
SMBUS_BATT_SDA: 0.5V

So these are DIODE mode readings and likely denotes them to be ok but let us confirm.

Now use DC voltage mode on your meter. Apply power to the logic board.

Red meter probe onto SMBUS_BATT_SCL, black meter probe to ground.

What is the measurement?

Repeat with SMBUS_BATT_SDA. Each should be ~1v8 if ok.

[Opunktvoll]

Re: 820-02098 - a2442 - power cycling

Sorry, my mistake.

I can confirm both SMBUS_BATT_SCL and SMBUS_BATT_SDA are at 1v8.

[Opunktvoll]

Re: 820-02098 - a2442 - power cycling

After some more testing:

PP5V_S2SW_USBC01 and PP5V_S2SW_USB23 are both 0V because enable is missing (P5VUSBC01_EN and P5VUSBC23_EN, both coming from the CD3217.. ). Acc. To schematic this is critical.
No matter if powered up via magsafe or each USB port, it's always missing. Could this be the reason maybe? Unfortunately I don't have a working board to compare.

Maybe this also explains the power cycling of the USB-C meter.. I once read this is always related to an issue with the CD32s in some way.

[Davitzz]

Re: 820-02098 - a2442 - power cycling

After some more testing:

PP5V_S2SW_USBC01 and PP5V_S2SW_USB23 are both 0V because enable is missing (P5VUSBC01_EN and P5VUSBC23_EN, both coming from the CD3217.. ). Acc. To schematic this is critical.
No matter if powered up via magsafe or each USB port, it's always missing. Could this be the reason maybe? Unfortunately I don't have a working board to compare.

Maybe this also explains the power cycling of the USB-C meter.. I once read this is always related to an issue with the CD32s in some way.

Hello, i have the same port cycling problem at 20V in the same board, did you solved in someway?