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MBP 820-3113. Liquid damage.

gcain

gcain

New member
[FONT=&quot]Significant liquid damage with pins 4 & 5, as well as the traces totally dissolved (Red wine, Arg!).

[FONT=&quot]Replaced U5410: Pins 4 & 5 completely burnt out.[/FONT]
I ran a wire from U5410 pin 4 to R5410 Pin 2 and from U5410 Pin 5 to R5410 Pin 3 to try and get around the traces being burnt out. (Can someone confirm this is right please?!)

Replaced R7403 which was dead.


Board now powers up but fan runs high & R7403 is reading erratic voltages.

Can someone suggest some measurements I should be taking?


I'm new to the board repair business and know enough to be dangerous. :)
With a little direction though I should find my feet really quickly. All suggestions and input appreciated.[/FONT]
 
D

dukefawks

Administrator
U5410 is not important right now, the board will work without for now.
Measure both R7402 and 3 from F7040 to the actual pin on U7400 to see if the traces are ok.
ALL_SYS_PWRGD present?
 
gcain

gcain

New member
dukefawks said:
Measure both R7402 and 3 from F7040 to the actual pin on U7400 to see if the traces are ok.
Click to expand...

I get continuity from F7040 to U7400:pin3, if I understand your question correctly.

dukefawks said:
ALL_SYS_PWRGD present?
Click to expand...

R7402:pin1 is bouncing between 1.2v & 1.4v.
U7400::pin3 measured at Pin1 of R7410 is giving me 12mV. :/
F7040 is giving me 12.59v on both ends.
ALL_SYS_PWRGD: U2650::pin1 is giving me 3.2v.
 
A

aprendiz

Moderator
Check resistance between F7040 and pin 1 from U7400, the value should be about 182K (the value of R7403), now measure resistance between F7040 and pin 48 from U7400, the value should be about 150K (the value of R7402)....
 
gcain

gcain

New member
Thanks for the instructions!

U7400 doesn't have a pin 48, it stops at 40 (or 41 really) right?
 
gcain

gcain

New member
Ahhh No!
I got two boards mixed up!!

I'll get the proper readings in a moment.
 
Last edited:
gcain

gcain

New member
aprendiz said:
Check resistance between F7040 and pin 1 from U7400, the value should be about 182K (the value of R7403), now measure resistance between F7040 and pin 48 from U7400, the value should be about 150K (the value of R7402)....
Click to expand...


So, now that I have the right board. (sorry about that, I'm working on a bunch of old ones I haven't been able to fix).

I have no continuity between;
F7040 and U7400::pin1
F7040 and U7400::pin8.

Looking at it though, I'm not so sure there would be...
 
gcain

gcain

New member
I cleaned the points and checked again.

I'm getting 30 to 40 Mohms (it's not a stable reading) on both pins.


(Going to start checking every component btween U7400::pin1 and F7040)

Happened to get another 3115 in today and checked U7400 to F7040; Yep, 182 & 150k Ohms exactly. :/
This is good though, I have something to look for now.
 
Last edited:
gcain

gcain

New member
When I measure the resistors (7402 and 7403) I get the correct values.

7402 & 7403 have been removed, traces etc. cleaned up and replaced...

But the resistance between them and F7040 is still in the Mega Ohm ranges. On the working board I have here, it is 0ohms on Pin2 and then the expected 182k & 150k on Pin1, respectively.

Is it a single wire between F7040 & the two resistors?

What could be messing with the resistance?
 
gcain

gcain

New member
F7040 to C7513::pin1 is 0Ohms.
C7513::pin1 to R7402 & R7403 is 6MOhms.

So I'm guessing if we jumper-wire from C7513::pin1 to R7402 & R7403 I should have power back there. :)

Yeeew, going to give it a try and report back.


Edit:
Could one of the capacitors on that line be faulty and causing this issue?
Maybe the issue is a component and not the trace.
 
Last edited:
gcain

gcain

New member
Still no chime or picture or ram-beeps.

I'm getting the 12.6v at R7402 & R7403 now, but the behaviour is exactly the same.
 
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