820-01521: Liquid Damage

[baker_jeff]

First time working on one of these, oh boy (Late 2018 MacBook Air).

Liquid hit in the U3200. One one USB-C port, 5v @ 0.001amp. The 2nd port would flash on/off/on/off.

I replaced U3200 and a couple of the small caps and resistors in that area that looked gross. Now, both USB-C ports show 5v @ 0.03amp, but occasionally it will flash on/off/on/off on the one port still.

I'm getting my LDO outputs on both CD3215s.

TBT_PWR_EN is 0v. Should I be following this or am I barking up the wrong tree?

Thanks in advance!

Jeff

 

[2informaticos]

Check what happens with both charger and battery connected.
Do you get 1V1 LDO on both ports?

 

[baker_jeff]

Hmmm with everything plugged in, I'm getting 20.5v and 0.00a. T2 getting warm, nothing else that I can tell.

 

[2informaticos]

Why do not check for some board voltages now?
Battery has some charge?
Try to turn board on...

 

[baker_jeff]

Gah, I just came back to test this and it's back to 5.15v @ 0.01a, both ports.

 

[baker_jeff]

I'm getting 1.1v LDO line on both.

 

[2informaticos]

Looks like more components affected by corrosion there.

 

[baker_jeff]

Coming back to this one. Things "look" clean. No broken traces that I can see, no really nasty components. Should I be hunting down TBT_PWR_EN?

 

[2informaticos]

Actual PPBUS_G3H voltage?
Do you get AWAKE and SLPS2R voltages?
Can you enter to DFU mode?

 

[baker_jeff]

PPBUS_G3H showing 12.3v, but seems to flicker down to 10v or 0v every few seconds. PP1V8_AWAKE is flickering between 0v and 0.7v.

No luck/signs of life trying to get into DFU mode.

 

[2informaticos]

On T2 boards, all voltages derive from PPBUS_G3H.
Check for short on secondary power supplies.

 

[baker_jeff]

Coming back to this one, the "top" USB-C port isn't staying on. With the voltage reader plugged in the screen flickers on/off/on/off/on/off etc. The bottom port reads 5v 0.01amp. I replaced both CD3215.

I tried with a diff USB-C port piece and the top port started working. Put the original back... still working. This one is effing frustrating.

I'm still getting 12.3 on PPBUS. Using this list as reference: https://logi.wiki/index.php/T2_and_CD3215_Power_on_Sequence

PPBUS_G3H: 12.3v
PP3V3_G3H_RTC: 3.3v
PP3V3_G3H: 3.3v
PP1V8_SLPS2R: flickering between 0.00v and as high as 0.9v. It flickers up consistently every 0.5 seconds and then back to 0.00v. Checked restistance and it is shorted. Following this...

 

[2informaticos]

Which is the exact ohm value to ground at PP1V8_SLPS2R ?


What about other AWAKE and SLPS2R voltages, any pulse at least?

 

[baker_jeff]

In resistance mode: PP1V8_SLPS2R is 0.9ohm

I happened to get in a working board (yay!) and it is getting 4.5kohm.

I injected shy of 3v and can't find the damn problem even using Flir. Lots of areas getting warm... but nothing on this line.

 

[2informaticos]

3V injected into 1V8 power rail???

 

[baker_jeff]

Well... yeah. I bumped it from 1.8 to 2.8 as nothing obvious was showing up... unwise judging from your response?

 

[2informaticos]

What kind of PSU used?
Did you leave the amp limit at max?

 

[baker_jeff]

Tekpower... amp set to 5.2

 

[2informaticos]

You should get something like 2A ( a bit more) for 2v.
Something should heat with 4-5W.
Did you remove heatsink?