820-2838 not turning on (no s3 voltages)

ytesfay80

Member
This board had some liquid damaged but not too bad and the LCD connector was butned on pins 3/4 I have removed the connector. I get a green light but it doesn't turn on. When the battery was plugged in the charger light would turn orange so the battery is being recognized

Here is a list of areas that had any liquid damage before I put flux and heated those components. I have not put it in the ultrasonic yet.
q7055
u7201
c7012
l6995 area
j5700 tpad connector
c7050 r7052 area of isl6259
pin 3 u5402
u7870
r5127 area(SPI_ALT_MOSI)
Q9302
q7330/35
u7840
c7012/13 were burned and replaced

I first replaced r7051/52 & C7050 and the pad on Pin 1 of R7051 was gone and there was no continuity from Pin2 of c7050 to Probe 556 so I ran a wire from C7050 to Pin 1 of R7051 & Probe 556.
That still didn't solve the issue so I replaced the ISL6259 and still same issue.
Resistance Pins 17/18 - 2.9ohms Pins 27/28 - 20.8ohms

U7201 had some liquid damage but no components look badly damaged. Here are some voltages of U7201
Pin 23(VIN) - 8.4v
Pin 22(VREG3) - 3.3v
Pin 29(VREG5) - 5.02v
Pin 12 - 0v
Pin 4 - 0v
Pin 21 - 3.51v
R7251 has 0v on both sides.
R7813 also 0v on both sides. (PM_SLP_S4_L)


I shorted the power pads next to the tpad connector and measured SMC_ONOFF_L going down to 0v and it still didn't turn on.
 
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2informaticos

Administrator
Staff member
"Pin 12 - 0v
...
Pin 21 - 3.51v"
This not possible, unless you have corroded trace; or did wrong measurement...
Look at schematic, check U7840 area. It should have same voltage at pins 2/3.

Also measure resistance to ground at L6995, in 200K scale.
You know, should be higher than 30K.
 

ytesfay80

Member
I didn't push my probe all the way into the pin. Pin 12 is actually 3.43v. Pin 2 of U7840 is 3.43v and Pin 3 is 3.51v

L6995 in 200k scale if I did correct shows around 66Kohms
 
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ytesfay80

Member
Threw this in the ultrasonic and I shorted the power pads and the fan spun so it looks good. I will get some sleep, test everything together and update later today.

Update: Everything is working fine now.
 
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ytesfay80

Member
I did an ASD OS test and it is telling me the Current(ID0R) DC IN sensor is reading below the low point.
I took an I/O Board+Cable from a 2011 MBA that passed the ID0R sensor test and I plugged it into this machine and that sensor still failed.

R5481 and the surronding SMC area look spotless and the resistance measured fine. I believe it was measuring somewhere around 0.35v in voltage mode

In EFI version here is the hardware profile reading.

Low-Limit: 0.1A
High-Limit: 3.29A
Description: Current Sensor DCIN 0 Rail AMON
Reading 0.04A
 
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ytesfay80

Member
I got a ID0R reading from a working 2011 MBA that passed the sensor test and this is what it showed on the hardware profile.
Low-Limit: 0.0A
High Limit: 3.5A
Reading: 0.000A
 

dukefawks

Administrator
What has the IO board to do with this, please explain?

This is of course an issue with the current sense circuits on the ISL6259.
 

ytesfay80

Member
When I say DC-In I assumed that was the IO issue.
Pins 17/18 + 27/28 measure proper resistance. (2.9ohms & 20.7ohms)
I did do some repairs on Pins 17/18 as stated previously. I'm not sure if that is causing issues.

"(I replaced r7051/52 & C7050 and the pad on Pin 1 of R7051 was gone and there was no continuity from Pin2 of c7050 to Probe 556 so I ran a wire from C7050 to Pin 1 of R7051 & Probe 556)"

There is continuty all the way from pins 17/18 to the current sensing resistors.
 
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dukefawks

Administrator
Something is fucked in the current sense circuit. It is up to you what is wrong. Maybe wire is wrong or something.
 

ytesfay80

Member
Okay I made a foolish mistake I was running the test without the charger plugged in. I plugged the charger in and did the test and it Passed this time.

Thanks.
 

ytesfay80

Member
I ran the test again with the charger plugged in and it passed and the reading on ID0R was 2.1A. I removed the charger and did the test again and the reading showed 0.04A and failed.
 
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