820-00928 20V only charger, shows low battery on screen

[Rlab]

Hi, this is my 1st post !
This 2017 macbook pro 15" shows low battery icon on screen powered only with the charger in all 4 tipe-C ports.

With the charger + battery, PP20V_USBC_ is pulsing from 5V to 0V on 3 ports, the port managed by UB400 gets 20V and shows apple logo for 2sec and then turns off.
If I try the port managed by UB300 imediatelly after trying the "good port" managed by UB400 PP20V_USBC_ will jump to 20V and will show on screen the apple logo for 2 or 3 sec an then turns off but PP20_USBC_ will stay at 20.26V.
the port managed by U3100 is the only port that boots through SMC bypass with the fans in full speed and does not recognize the battery.
the port related to U3200 will stay pulsing from 5 to 0V.

U3100, UB300, U3200 have been replaced in that order together with U7000.

Before the replacements this macbook was also showing low battery icon using only the charger in all ports with 20V on PP20V_USBC_ and with the charger + battery had 5V in 3 ports but had 20V on port managed by UB400 showing low battery as well.

some measurements:

PPBUS_G3H 12.57V
PP3V3_G3H 3.4V
SMC_BC_ACOK 3.4V
CHGR_BMON 0.0V with & without battery
PP5V_S4_X_USBC 0.0V
PP5V_S4_T_USBC 0.0V

This motherboard had no sings of water damage or corrosion, any thoughts?

Thanks!

 

[2informaticos]

First of all, welcome to the forum!

Compare diode mode readings on the 4 LDO rails of all CD3215 chips.

If board starts in safe mode through one port, there should be at least one SMC sensor issue.
But you still have to fix USB-C power issue.

 

[Rlab]

Thank you very much !

I don't see a significant difference between the readings on diode mode...

U3200
PP3V3_UPC_XB_LDO 0.476
PP1V8_UPC_XB_LDOA 0.488
PP1V8_UPC_XB_LDOD 0.454
PP1V1_UPC_XB_LDO_BMC 0.471

U3100
PP3V3_UPC_XA_LDO 0.477
PP1V8_UPC_XA_LDOA 0.492
PP1V8_UPC_XA_LDOD 0.458
PP1V1_UPC_XA_LDO_BMC 0.477

UB400
PP3V3_UPC_TB_LDO 0.480
PP1V8_UPC_TB_LDOA 0.495
PP1V8_UPC_TB_LDOD 0.458
PP1V1_UPC_TB_LDO_BMC 0.475

UB300
PP3V3_UPC_TA_LDO 0.477
PP1V8_UPC_TA_LDOA 0.497
PP1V8_UPC_TA_LDOD 0.463
PP1V1_UPC_TA_LDO_BMC 0.479

What do you think?

 

[2informaticos]

Now check voltage on all LDOs.
Be aware, 1V1 LDO should appear only on the port where the charger is connected.

 

[Rlab]

Voltage on all LDOs:

U3200
PP3V3_UPC_XB_LDO 3.370
PP1V8_UPC_XB_LDOA 1.796
PP1V8_UPC_XB_LDOD 1.796
PP1V1_UPC_XB_LDO_BMC 1.1

U3100
PP3V3_UPC_XA_LDO 3.382
PP1V8_UPC_XA_LDOA 1.793
PP1V8_UPC_XA_LDOD 1.806
PP1V1_UPC_XA_LDO_BMC 1.1

UB400
PP3V3_UPC_TB_LDO 3.387
PP1V8_UPC_TB_LDOA 1.802
PP1V8_UPC_TB_LDOD 1.793
PP1V1_UPC_TB_LDO_BMC 1.1

UB300
PP3V3_UPC_TA_LDO 3.380
PP1V8_UPC_TA_LDOA 1.79
PP1V8_UPC_TA_LDOD 1.79
PP1V1_UPC_TA_LDO_BMC 1.1

I checked them in all ports, all showed up

 

[Rlab]

So, If LDOs are present what could it be the next suspect?

 

[2informaticos]

Without battery, do you still get low battery icon through all USB-C ports?

Did you connect battery data cable, when you tried with battery?
Apart of the connector fixed with big screw...

 

[Rlab]

Yes, I still get low battery icon only powered with the charger (original 96W) in all USB-C ports

yes, I connect the data cable when tried battery. without data cable reacts the same as without battery.

How the "low battery icon" circuit works?

 

[Rlab]

Any suggestions ?

 

[2informaticos]

Try another known good battery.
Some boards don't boot properly without good battery.

 

[Rlab]

Ok, I will try and will go back to update the post.

Thank you, have a good weekend !

 

[Rlab]

Just tried a known good battery from a working mac and a new battery .
unfortunately this board still doesn't want to work, although there was an improvement.

With the charger + good batteries, PP20V_USBC_ keeps the 20V and shows the low battery icon.
the down side now is that it doesn't boot even SMC bypass doesn't help..

Any ideas?

 

[2informaticos]

Post levels for PM_BATLOW_L, SMC_ONOFF_L, PM_RSMRST_L and PM_PWRBTN_L.
Trigger SMC_OMOFF_L and check for drop pulse at PM_PWRBTN_L at same time.

Be sure to use original 87W charger.

 

[Rlab]

Wile doing the drop pulse check at PM_PWRBTN_L by triggering SMC_ONOFF_L this Macbook pro A1707 turned on !
since then its been working like a charm !
@2informaticos what sorcery is that ?! - Thank you very much !

I'm posting the values you requested for future reference.

PM_BATLOW_L 3.31V
SMC_ONOFF_L 3.40V
PM_RSMRST_L 0V
PM_PWRBTN_L 3.3V

 

[2informaticos]

"PM_RSMRST_L 0V"
Are you sure about this???
Does it go high when press power button?
If stays low, PCH cannot start power on sequence.

 

[Rlab]

Yes, I'm sure. PM_RSMRST_L is not pressent if the computer is off even if it has charger + battery conected.

Once the power button is pressed PM_RSMRST_L goes to 3.29V

 

[2informaticos]

If goes high when pressing power button, is OK.
Some boards don't have this signal high in off state; got crazy with a 3662 board, when I faced this first time.