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Liquid damaged A2141 820-01700 Only powers on with Battery

EsteTron

EsteTron

Member
I have an 820-01700 that had corrosion under U3100 CD3217.
Replaced IC and now device pulls 5v at .3 Amps on charger alone. PPBUS gets 12.3v.
When connected to battery, it turns on and boots up to desktop just fine but does not charge. Ammeter reads 20v 0. amps with battery connected.
Replaced ISL9240 to no avail.
Replaced the CD3217 that was next to the corroded one just incase, but still same results.
 
2informaticos

2informaticos

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If board boots with battery, but doesn't switch to 20V with charger alone, the problem is on USB-C area for sure.
Probably some corroded resistors, or traces.
All 4 ports have exact the same behviour?

Compare diode mode readings around CD3217 chips between left/right ports.
Inspect U2890 and its adjacent resistors.
 
EsteTron

EsteTron

Member
Sorry for the delayed response.

All ports have the same issue.

Diode mode readings between and left and right ports read the same. Also compared with a donor board.

U2890 and nearby resistors read normal. Compared using working donor board.

The board has trace damage on Test pad UPC_XA_FUALT_L, but diode mode reading on this line compared to a donor is the same, so I think this is more of just a test point and not a via or trace.

I am missing PP5V_S4_X_USBC.

Just for sheer curiosity, i connected a charged battery and attempted and connected a USB to see if it was detectable in system report.

System report would detect a connected USB in all 4 ports but I would get an error saying that USB needs to be connected to a USB port that has power.
So there is some data going through, but no power on the ports.
 
EsteTron

EsteTron

Member
This could be where the issue lies. 5V_G3S is not present anywhere on the board. Is the rail suppose to be always present? It looks like this line is created by U7650. I see there is an enable signal for P5VG3S_EN_R reading 0v. On my donor board, it looks like it is 3.3v.
 
EsteTron

EsteTron

Member
Is it possible that U7800 is the issue? P5VG3S_EN signal is 0v. I'm curious as to how this computer still powers on to home screen with battery connected.
 
EsteTron

EsteTron

Member
Following the power sequence guide, I have all slpr and awake signals and voltages up until PMU_PVDDMAIN_EN .
 
2informaticos

2informaticos

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Even CPU power supply controller (U7100) is powered up from 5V_G3S.
Machine can't work without this voltage...
 
EsteTron

EsteTron

Member
5V_G3S is only present (5v) when battery connected.

PMU_PVDDMAIN_EN comes from U7800 but is not present.

CHGR_INT_L is 1.8v
PCH_RTC_RESET_L is 3v
CHGR_CBC_ON under both U7800 and U7000 so I am unable to test if it is sending a signal to U7800 to turn on.

This unit is not detected in DFU mode. How it stands, the USB c ports are not actually getting power with a battery, without a battery, or in DFU mode. I don't believe it is a T2 issue since the ports are not turning on or being detected in DFU mode. I'm leaning toward this being an issue with the TBT controller next to the corroded CD3217. Unless you think there is another point of interest.
 
2informaticos

2informaticos

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UPC_XA_FAULT_L is an error about USB-C port, sent out by U3100; goes to PCH, via R1845.
You must have 3V at all these fault signals, R1843-46.
Incorrect value, will block 5V output power to USB devices.
BTW, only the port with connected device should get 5V.

Of course, I'm talking about the case when board is RUNNING with battery connected.
I was thinking your previous posts reffered to same case too.
Seems that you mix the states, when board runs with battery and also posting something about only charger, when baord is off.

Detecting the problem about no 5V output for USB device (battery connected), may help to diagnose why the ports don't switch to 20V (charger alone).
 
EsteTron

EsteTron

Member
Interesting. I am glad that you point that out. Fault signal is 0v on all 4 resistors. Comparing with donor board has same diode reading of 0.66.
When connected to battery and running, it is 3.3v and pull 20v, 0amps.

When testing on donor board, 3.3v is not present on Fault line until device pulls 20v at 0.6 amps
 
EsteTron

EsteTron

Member
Comparing diode reading between donor board and I discovered that PP5V_S4_X_USBC is reading 0.34 on patient board but 0.5 on donor board.
 
EsteTron

EsteTron

Member
UPC_X_5V_EN reading 0.61 on this board and 0.53 on donor. I am not sure if that is enough variance for to to be a concern.
 
2informaticos

2informaticos

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5V sould appear at L3500, or LB700 when USB device is connected on the corresponding port.
Voltage may be disabled is a fault signal is detected on that USB port.

Not sure if you've seen Louis video about ISL95870A (GAY) chips.
You should check the one with lower diode mode reading on the coil.
Also check which side of the coil has the lower value.
 
EsteTron

EsteTron

Member
I was reading in a previous post about that. When you say that 5v appears on those coils when a USB device is connected, would that include a charger, or something else like an USB mouse?

I do recall a video talking about replacing the ISL95870A on new models with an older ISL.

L3500 is reading 0.34 on both sides.
LB700 0.5

So U3500 is of interest. Both sides of L3500 are reading the same in diode. I removed L3500 to get a better reading and I am getting a lower reading on Pin 1 on U3500 side.
 
2informaticos

2informaticos

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Then change U3500.
The MLB should send out 5V to USB port only if external device requires it; like pendrive, mouse, not charger.
 
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