820-3437 Water near display connector, no display

[down1nit]

Came in with lots and lots of damage near J8300 display connector. Replaced, measured OK, many support components replaced as well. Tested OK on bench, got picture and backlight, cleaned up and ultrasonic'd JUST THAT AREA. 99% alcohol bath in that place and oven.

Retested after 100 C degrees oven for a couple hours, and now there's no picture.

I've re-replaced the connector, just in case flux got cooked inside being careful to use only as much flux as i need. No change. I'm not 100% sure what to look for, all rails seem fine, but i've not dug super deep.

 

[2informaticos]

Missing image and backlight at same time?
Do you still get external video and USB activity?

3V appears at pins 18/19 in the first seconds (when chime, if)?
DP_INT_HPD goes high at same time?

 

[down1nit]

Ah, no chime. No video no usb activity. Wasn't expecting that. I'll check reset circuits and power lines more thoroughly.


3v does not appear at 18/19, no signal at DP_INT_HPD_CONN

 

[down1nit]

Rails:
PPDCIN_G3H: 16.4
PPBUS_G3H: 8.6
PP3V42_G3H: 3.42
PP3V3_S0: 3.3
PP3V3_S3: 3.3
PP3V3_S4: 3.3
PP3V3_S5: 3.3
PP3V3_SUS: 3.3
PP5V_S5: 5.1
PP5V_S4RS3: 5.1
PP1V8_S3: 1.8
PP1V2_S5_SMC_VDDC: 1.2
PP1V05_S0: 1.07
PP1V05_SUS: 1.09
PP1V35_DDR_CLK: 1.38
PP1V5_S0: 1.54
PPVBAT_G3H_CHGR_R:
PPVBAT_G3H_CONN:
SMC_BC_ACOK: 3.42
PPVCC_S0_CPU: 1.775
PPVRTC_G3H: 3.3


Enables/Signals:

PLT_RESET_L: 3.36
SMC_RESET_L: 3.42
RTC_RESET_L: 3.32
PM_SYSRST_L: 3.34
PM_RSMRST_L: 3.30
SMC_PM_G2_EN: 3.4
PM_SLP_SUS_L: 3.35
PM_SLP_S0_L: 3.35
PM_SLP_S3_L:
PM_SLP_S4_L:
PM_SLP_S5_L:
PCH_PM_SLP_S0_L: 3.35
ALL_SYS_PWRGD: 3.34
S5_PWRGD: 3.3
CPU_PWRGD: 1.069
SMC_DELAYED_PWRGD: 3.45
PM_PWRBTN_L: 3.4
PM_BATLOW_L: 3.35
SYSCLK_CLK32K: 32.9K present
25MCLK: 25M present
PCH_INTRUDER: 2.26
PCH_INTVRMEN: 3.06
PCH_SRTCRST_L: 3.3

Doesn't look like problems, INTRUDER/INTVRMEN are lowish but I think that's normalish with a relatively cheap Multimeter? Should I try a lower resistance pullup? I'm going to reflash bios and check spi resistors but they appear OK.

Is this a good case for heating the cpu edges at least or stay away?

 

[2informaticos]

All mentioned voltages and signals look good.
If PLT_RESET_L is high, PCH understood the power sequence is complete.

There should be a data communication problem.
Start with BIOS and SPI resistors.

 

[down1nit]

BIOS reflashed using known good from your post in another thread. I used a good programmer and verified. Resistors are fine.

I found damage near U3220 and U7701 the first time I looked over it. Replaced those chips outright, cleaned up area, just remembered that. Don't think there's any critical data lines but I'll check their pullups etc.

 

[down1nit]

Spent a good while checking data lines. SMC nets, PCH, everything on page 40, around u3220 and around u7701.

Is there somewhere else i'd be good to check?

 

[2informaticos]

Maybe accumulated crap under CPU; heat it for test (with quality flux).
I recommend to reball SMC first.