820-00850 no power - 5v

LCDR2

Member
Hello, long time no post.

I have a 820-00850 board which has no power, USB provides approximately 5.2v on all ports and 0.05 / 0,06 amps.

We have got
PPBUS_G3H 12.3v

Have not got
PP5V_G3S

I'm unfamiliar with exactly how this model works, aside from a few of louis' videos.

Looking at the board I saw corrosion under Q3440 which was missing pin 3 on the chip side so will need to be replaced. Is this enough to stop the laptop from booting?

The rest of the board looks OK. Is it worth reflowing the U3100 chip on that part of the board?
 

2informaticos

Administrator
Staff member
Q3440 is involved in the communication with the charger on that port.
All ports get 5V only?
Replace Q3440 before trying other things on the board.
 

LCDR2

Member
Update. Tested all ports again.

One USBC port only draws 0.01A .

I'm not sure how to differentiate which port it's connected to at this stage. I'm running tests at varioius points, and will post below.

All draw 5.22v v with no reset
J3300 side

CircuitTop (0.01a draw)Bottom (0.07 / 0.08a draw)
USBC_XB_USB_TOP_P2.5v steady1.5v (varies)
USBC_XB_USB_TOP_N2.68v 1.04v
USBC_XB_CC1_CONN1.0511.6v (varies)
USBC_XB_CC2_CONN0v1.6v (varies)
USBC_XA_USB_DBG_BOT_N1.55v2.588v
USBC_XA_USB_DBG_TOP_N1.8v1.75v
PP3v3_G3H700mv (decaying)3.3v
PPBUS_G3H1.5v (decaying slowly)12.27v

OK so....

One port does not provide main power rails to board which I discovered after testing outputs from USBC ROM chip.It didn't occur to be me to run seperate tests.

I'm not quite following yet how one port can work through a circuit, but when connected with the other port, it does not work.
I have swapped the USBC connector, and the USB connector on the board looks OK.


Is this a U3100 issue or a U3200 isssue ? I am having trouble separating out where the fault is.

Hope this information helps clear things up. I will post more after lunch!
 

2informaticos

Administrator
Staff member
Do you get 5V on all ports now?
R7020 gets voltage?
Post diode mode to ground at PPBUS_G3H; be sure F7000 is good.
 

LCDR2

Member
5.21v on all ports.
3 ports draw 0.7a
1 port draws 0.1a

R7020 is getting voltage (5.2v) ONLY when connected with ports drawing .7a, NOT with port drawing 0.1a

F7000 On"working" usb 12.29v on '0.1a" usb we get 1v
 

LCDR2

Member
PPBUS G3H 0.332v diode mode to ground (assuming I did it right)

Issue appears to be localised to something going on with that one port.

I am assuming my issue is with U3100 since that was the only area of damage I could see.

Does that correlate with the port that is only drawing o.1a?

It's the port closest tothe back of the laptop / heat sync.
 

2informaticos

Administrator
Staff member
Yes, the problem is located on the "0.1A" port.
Use boardview to locate corresponding CD3215 chip.
You can also check which CD3215 doesn't generate 1V1 LDO.
 

LCDR2

Member
Update

Reflowed area around suspected damaged CD3215

Now all ports get 5.21v and 0.07a / 0.08a

All ports deliver power to F7000 (12.29v) and R7020 (5.2v)

Does not continue to 20v success :(
 

LCDR2

Member
Seems to be

PP1V8_SLPS2R - 1.8 volts (pulsing / not stable)
PP1V8_AWAKE - 1.8v
PP1V1_SLPS2R 1.1v
PP0V8_SLPS2R 0.79v
PP0V82_SLPDDR 0.82v
PP3V3_AWAKE 3.37v
PPVDDCPUSRAM_AWAKE .8
PP0V9_SLPDDR .9v
PP1V1_SLPDDR 1.1v
PP1V2_AWAKE 1.2v
PPVDDCPU_AWAKE 0.754



Will try DFU
 

LCDR2

Member
Hello

Tried DFU.

Not sure how long I am supposed to wait. It appeared to work but laptop didn't boot like in video. Got to the point where it got "stuck"

I get this error, sometimes, when I try to run again.

I didn't get this error when I attempted the second time (where the progress bar paused like in your video)

Laptop still drawing 5.2v 0.08a :)

1609822717888.png
 

2informaticos

Administrator
Staff member
Try with Catalina and Big Sur too in the second machine, if you don't exactly know the macOS installed in T2 machine.

"PP1V8_SLPS2R - 1.8 volts (pulsing / not stable)"
This could be a problem; should be stable, as all other SLPS2R voltages.
 
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