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Old 11-07-2021, 11:39 PM   #1
wnt2fx
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Default 820-01700 5v 0.25 a

Hello everybody, I am a little desperate understanding this t2 board. Somebody worked on it before ( u3100) I guess reflowed. Liquid damage hit mainly the right wing but also u7800 area. L7811 looked horrible.

First thing I did was carving out a short on ppbus ssd0. Not so much maybe 2 three layers deep "just" in the extent of pad 1 of c9573.

I do not have the battery here.
On all ports except on the master u3100 (XA= 0.01A and no pbus) I get 5v going up in 2 steps within 2 seconds to 0.24A and stays stable there. The only thing I notice gets warm is the t2 area and pp3v3_g3h_rtc supply. Not hot, only 30 C

The last line in power sequence I get is PMU_ACTIVE_READY If I remeber right it is at 1.7v. I did not check all lines in the sequence there but many and they are all present in correct value e.g.

PP1V1_SLPDDR

PP0V9_SLPDDR

PP0V82_SLPS2R

PP0V8_SLPS2R

PP1V1_SLPS2R

PP1V8_SLPS2R

https://logi.wiki/index.php/T2_and_C...28820-01700.29

I do not have

PMU_VDDMAIN_EN

I replaced u3100 but unchanged.

I checked some t2 lines to gnd ( logiwiki, me: redGND, blackGND )

PPVDDCPU_AWAKE 10-15 Ohm 18 19

PP0V82SLPDDR 30-40 Ohm 40 45

PPVSSCPUSRAM_AWAKE 100-120 Ohm 170 253

PP1V1_SLPS2R 1-2 kOhm 5,9k 5,3k

PP0V9_SLPDDR 40 Ohm 55 61

PP1V8_SLPS2R 4 kOhm 200k 13k


will take a big nap now. After some hints / ideas I am more than willing to note down more measurements. best regards,

k
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Old 11-08-2021, 11:29 AM   #2
wnt2fx
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Default Re: 820-01700 5v 0.25 a

Ultrasonic cleaning --> still [email protected] on three ports, still [email protected] and so no PPDCIN_XA_G3H_F output on primary port.

The power sequence says "H9M LOAD SECURE ROM, SMC BATTERY TRAP" right before creation of PMU_VDDMAIN_EN. I can get the battery today but wonder if this makes sense as long I have this amperage draw on three an no amps on primary port.

U9580, R5620, C9580, C9581, C9583, C9584 and C9574 were removed in my first test now they are back but no change. I removed them because the area looked hit and after removing R5620 it was clearly a short on PPBUS_G3H_SSD0_SNS. To dig down the short I first removed theese components to then find out that the board is burnshorted in pad1 of C9573.

I noticed a strong difference drop to GND on PP1V8_SSD0 (.06), compared to PP1V8_SSD1.
Injecting 1V draw about a half mA

also
PP2V5_NAND_SSD0
PP0V9_SSD0
have a lower diodedroptoGND compared to their _SSD1 equivalants but not so much.
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Old 11-09-2021, 09:16 AM   #3
piernov
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Default Re: 820-01700 5v 0.25 a

SSD chips are almost certainly dead. T2 won't initialize in that case. Must be replaced from donor board then must perform T2 DFU restore.
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Old 11-10-2021, 12:27 AM   #4
wnt2fx
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Default Re: 820-01700 5v 0.25 a

Hey piernov. Thanks for beeing here ! Generally: t2 must come from identical Board ?

Now, I don’t think that the t2 is dead:

Today I picked up the housing with battery and after I installed the logicboard I suddenly had 0.07A @ 19v input on all ports.
I just connected fans, audio, power button and touch bar connections, not the battery yet ! So I was wondering if any of the flex connected where crucial to negotiate 20v an disconnected one after another. But still, logicboard in the housing, nothing connected and 19V. As usual on USB-C Ampmeter - 96W charger.
I can not explain why I have no more 5v 0.25A / 0.01 A on main port symptomatic.

The board power cycles it seems to me. Every about 20 seconds the drawn amps drop to 0.01 for a seconds and the fan wants to kick in.

With battery plugged the draw raises slowly to about 0.8A before the reset / cycling occurs. The battery has some charge at least. When I disconnect the charger the board continues cycling and has stable voltages (until 20 seconds :-) on the few points I measured. No DFU recognition.

ppbus 12.58V.

correct value and stable until each 20 seconds:

all SSD0 and SSD1 voltages
PP3V3_G3H_RTC_X
all major SLPs
PP3V3_G3H_T
PP5V_G3S

How can I find out if t2 fails to fetch efi from nand or if it does not get to that point because some malfunctioning circuitry is the root ? What rails are clever to check now and/or would it be wise to take out the nand and check it?
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Old 11-19-2021, 01:00 AM   #5
wnt2fx
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Default Re: 820-01700 5v 0.25 a

Quote:
Originally Posted by piernov View Post
SSD chips are almost certainly dead. T2 won't initialize in that case. Must be replaced from donor board then must perform T2 DFU restore.
ah I was too fast. You wre for sure speaking about the nand and not the t2. ssd chips must come from donor board because of eSPI ?

I mean this board should be saved anyways but my first concern is data recovery here.

Every 20 seconds ppbus drops from 12.58V to 12.28V.

Please someone guide me on how to proceed with this one. thank you so much
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