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820-00281-10 liquid damage

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ChrisB

New member
Ok guys, on mobile so please bear with me.

i am at my wits end with this one, don’t get enough time to work on these as I have to help with customers on front and deal with phones etc. for rapid turnaround.

we got in this touchbar MacBook Pro that had liquid damage all down the USB-C on the touchbar connector side (pictured). So far I have changed:

caps relating to PP20V_XA, the USB-C controller chip and even as far along as U7000 where there was no liquid spilled. The problem I’m getting is at F3000 I get 5.2V but it pulses from 5.2V down to 0v and very quickly recovers. If I measure at F3001 I get 5.2V that also pulses but only down to around 4.8V and then recovers. This would suggest to me that something is shorted but I cannot find it.

PP3V3_G3H is present but pulsing.
PPBUS_G3H is 0.2v and not shorted.
U7000 is getting all voltages it needs but they are pulsing up and down.

the thing is, if I remove U7000 then measure at F3000 or F3001 then the pulsing stops and the voltages are 5.2V solid.

am I missing something here?

any help is greatly appreciated.
 
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ChrisB

New member
Sorry I made a mistake as I was going off memory last night. I replaced U3200 as it's F3001 thats pulsing down to 0v and back to 5.2v. U3100 had no liquid near it, it was all on U3200 side. F3000 is also pulsing but only to 4.8v

SMC_USBC_INT_L on R3038 is pulsing but from 0v-1.8-2v and back to 0v. I'm not sure if it's just trying to turn on, something shorts out and it dies again.
 
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dukefawks

Administrator
Do you have a known good charged battery to see if it will power on from battery?

I must say the board looks pretty fucked up :(
 
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ChrisB

New member
That's the result of a spillage. I can charge the battery somewhat from a bench supply tomorrow to see but right now we don't have a known good battery to test. its a shame too as the board now looks extremely clean and this area was the only place that came into contact with liquid. maybe a faulty USB-C flex?
 
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dukefawks

Administrator
You cannot charge a battery like that EVER!
Of course you should rule out a bad USB-C connector flex too. Got pictures of what the affected area looks like now?
 
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ChrisB

New member
I didn't try to charge it. original battery was giving 0.0V.

Tried a new flex, still pulsing.

I did some measurements and thought I would check PPVCC_CPU_S0 - 0.002 on diode mode. Am I right in thinking this is far too low? it would explain a lot..

I will get pictures tomorrow once it's had another ultrasonic.
 
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dukefawks

Administrator
The battery will show 0V when not connected to a board. As soon as you remove the flat cable it is disabled.

0.002 is very low, how much is it in Ohm mode?
 
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ChrisB

New member
in Ohm mode I'm getting 3.2 Ohms. Measured on C1701. PPVCCGT_S0_CPU also measures the same. Mt thinking now is that it is TRYING to switch on, encounters a short on the CPU line and then pulses down for protection?
 
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dukefawks

Administrator
3.2 Ohm is probably ok, but I have no reference board here of course. At least it is not a full short. Have you checked all other rails for shorts?
 
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ChrisB

New member
Hi guys, did a bit more measuring and found that I have no shorts on any rail I am testing, I am finding R6921 giving 5.02V when I think it should be 3.3v. swapped U7000 again just to be sure and still pulsing up and down. When I remove anything to do with PP3V3_G3H from the system such as U7000 then it stops pulsing. I tested this by removing R6923 which is a 0 Ohm resistor and the pulsing stopped but no PP3V3_G3H was present.

Diode mode measurement on R6923 is 0.320 but if I remove that resistor then pin 1 goes up to around .480 and pin 2 which is the G3H side stays at .320
 
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dukefawks

Administrator
Do you have anyway to measure the current being drawn on the USB-C connector? Just to confirm, are you using a REAL genuine Apple 87W charger and cable?
 
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