820-2936-B

[Anterweb]

I got this 820-2936-B with coke spilled inside it,

After putting through the Ultrasonic it came out spotless , It seems to want to try and boot without battery connected ( Gets half way through loading bar and the reboots )

But if I connect a known good battery the magsafe goes off completely and I have to unplug and plug back in the magsafe to get it to work again,

I cant see anything obvious the board looks good under the scope. Any ideas?

 

[2informaticos]

Check resistance between pins 17/18 and 27/28 of U7000.
Be sure Q7055 is not shorted I/O.

 

[Anterweb]

Check resistance between pins
17/18 = 8.13k
27/28 = 19.9 ohms

Be sure Q7055 is not shorted I/O.
Is not shorted to ground but is shorted from I/O testing with another board I see this shouldnt be the case,

The mac will boot on battery alone but only in SMC bypass and will boot on magsafe alone but again only in SMC bypass mode, if both battery and magsafe connected I can not turn on at all!

Presume Q7055 is dead and replace?

 

[2informaticos]

"17/18 = 8.13k"
Fix that, don't touch Q7055.
Check R7051/52 and their traces.

 

[Anterweb]

R7051 was bad, Changed that and now get 2.2 as scem says,

Now getting 140 k and slowly rising on pins 17/18 ? (what should I be getting here?}

Still same behavior,only boots in SMC bypass with either battery alone or magsafe alone. Does nothing with both connected but now does not shut the magsafe off anymore

Q7055 still has continuity between the top and bottom pins?

 

[2informaticos]

What is the exact PPBUS_G3H voltage (without battery)?

 

[Anterweb]

SO I went to check this and a couple of weird things from last night,
PPBUS_G3H voltage (without battery) = .220v
PPBUS_G3H voltage (JUST battery) = 11.96v

Magsafe green light is real dim and it will now only boot up from battery alone and does nothing with magsafe connected,

Also noticed when checking voltages that U7000 or a component very close to it is getting VERY hot when magsafe is connected , finger on board in that area gets a burn!

But as i said still boots fine with battery alone.

 

[2informaticos]

Check diode mode to ground on U7000 pins.
Pay atention to pins 2, 19, 20, 27, 28.

 

[Anterweb]

2 = ol
19 =.014
20 =.011
27 =.501
28 = .500

 

[2informaticos]

Renive U7000 and check again pins 19 & 20.
If good, replace U7000.

 

[Anterweb]

Renive U7000

Renive?? Did you mean reflow? or Remove?

If so how should I be measuring 19/20 and what should I expect a good reading to be?

 

[2informaticos]

Sorry for misstyping; I meant remove.
If U7000 is the culprit, you shouldn't get such low values (0.011/14), after removing it.