820-00840 liquid damage, no power

Victor Holley

New member
I have 820-00840 that does not turn on.

Two USBC ports had different activity.
Port #1 =5v, 0.17A steady
Port#2 20v immediately cuts off, 0A then restarts

Found one drop of water on the board.

That drop made corrosion at R7021, R7022 near U7000. No water under U7000. Test point for PPVIN_G3HP3v3G3H was corroded away. No continuity between C7078 and C6991. Replaced resistors and made jumper to bring back continuity of PPVIN_G3HP3V3G3H
Also test point TBA_CSOR_N is corroded away, but this looks like it does not make an open when missing.

Result: Port#2 is now 20v and 0amp steady


I searched forum and read posts. Learned that step one is make both usb c ports the same.
Diode mode of LDO rails showed a short on PP3v3_UPC_XA_LDO.
Replaced only this CD3215

NOW BOTH usbc ports are THE SAME
20v, 0.00A

Measured PPBUS_G3H with no battery connected. Voltage= 1.1v declines to 0.95v and boosts to 1.1v, repeats pattern.

Diode mode on PPBUS_G3H = 0.429

I stopped here to ask what would you do with this board next?
 

2informaticos

Administrator
Staff member
Post some U7000 voltages; P_IN, AUX_DET, VDDA/P, SMC_AUX_OK, CHGR_A/BMON.
Post ohm resistance over C7020/23 caps.

Try to start in SMC bypass mode.
 

Victor Holley

New member
P_IN = 20.56
AUX_DET = 4.92
VDD/A = 3.01
VDD/B = 5.11
SMC_AUX_OK =_3.41
CHGR_AMON = 3.4
CHGR_BMON = 0
c7020 2.9
c7023 2.9
SMC BYPASS was unsuccessful for fan spin
 
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Victor Holley

New member
I replaced earlier the two corroded resistors 7022 and R7021 before I took the U7000 area measurements and reported them here.
On inspection, I realize that U7000 was not even--I must have nudged it during resistor replacement. I reballed it and returned it to the board.

Now Usbc port activity is 20v, 0.03A switching to 0A and back to 0.03A, or steady 0A

PPBUSG3H = 0.08v
PPBUSG3H diode mode =0.400
VDD/A = 1.09v
VDD/P is same 1.09v
 

Victor Holley

New member
My preference would be to understand what U7000 does so that I can troubleshoot on my own.
For example, I can see that U7000 has power in from usbc charger, after it passes current sensing resistor R7020
I see CSIN and CSIP which are the two sides of the input current sensing circuit.

I see AUX_DET which probably stands for something like auxiliary detection which must be when something other than a charger is plugged into usbc

SGATE and AGATE I recognize them as common in chips that control mosfets--I guess this is how the chip switches the mosfets

I don't know MPM Detection

PP3v3_G3H seems like another power in

I see a couple of data lines where U7000 talks to SMC

I see HPWR_EN_L which is an enable for U7000, I'm not sure where it is from

CHGR AMON and BMON I recognize as common lines for charging chips but I don't know what they do. I would like to know these lines.

There is an output PM_EN_P3v3G3H which probably tells the power management chip that usbc has been plugged in?

BGATE line probably goes with SGATE and AGATE to control the mosfets

CSOP and CSON are current sense circuits for the chip outputs?

Ultimately U7000 talks to SMC and if it is told yes then it switches the mosfets to generate PPBUS_G3H from the DCIN and/or from the Battery, and it uses DCIN to charge the battery. Is this right?
 

2informaticos

Administrator
Staff member
No datasheet available.
But you can compare with an old chip, like ISL6255/57; VDD/P described there.

I said to check R7075, take your time.
If good, then should get equal values in second post too.
You've got wrong voltages after reballed U7000.
So chip is fried, or bad solders.
 
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