820-4924 - PP5V_S0/S3 Missing

[pws6074]

Guys,

The board has water damage.
The thing is "works" (turn on, get the login screen, but the keyboard and tracks doesn't), bc the board looks like a S****, i decide before start troubleshooting drop on the supersonicmachine.
Well, after that, the PP5V_S0 /S3 is missing.

Any hint at this point?

 

[TCRScircuit]

USC knocked something off. Look at the board under the scope very closely

 

[pws6074]

What is USC means?

 

[TCRScircuit]

Ultrasonic cleaner. Never clean a board before prefroming localized reflows of the damaged areas.

 

[pws6074]

Yes, for sure. Like i said: After the USC, the S0/S3 is missing, but S5 still there.
SMC_RESET is there 3.4 i get green light

 

[pws6074]

Pp3v3_s5_reg = 3.3v

 

[dukefawks]

Could be anything. Check all the usual, U1950, U1900, U6100 and termination resistors, PPVRTC.

 

[pws6074]

u1950
Pin 1 = 0
Pin 2 = 0.90v
Pin 3 = 0
Pin 4 = GND
Pin 5 = 0
Pin 6 = 0
Pin 7 = 0
Pin 8 = 3.4V

u1900
Pin 1 = 3.3V
Pin 2 = 3.3V
Pin 3 = 0V
Pin 4 = 0.90V
Pin 5 = 3.34V
Pin 6 = 3.34V
Pin 7 = 0V
Pin 8 = 0V
Pin 12 = 0.4V
Pin 13 = 3.4V
Pin 14 = 0V
Pin 15 = 0V
Pin 16 = 0V

u6100
Pin 1 = 0V
Pin 2 = 3.34V
Pin 3 = 3.34V
Pin 4 = 0V
Pin 5 = 3.34V
Pin 6 = 3.34V
Pin 7 = 3.34V
Pin 8 = 3.34V

 

[dukefawks]

By checking I meant for corrosion. Check if board is power cycling on L7520 preferably with a scope as multimeter can be to slow to catch the pulse.

 

[pws6074]

Duke, i don't have scope. Have another way?

 

[dukefawks]

Connect a LED with a 100 ohm resistor to the 5V output on L7520. Should be able to see it blink.

 

[pws6074]

Can i buy something like that for?
https://www.ebay.com/i/222540610199?chn=ps&dispItem=1

 

[dukefawks]

If you don't want to spend any money go find some old CRT scope for $20. Any 10MHz piece of crap will suffice.

 

[pws6074]

I just bought a scope and tested L7520 and i get small pulse.

 

[dukefawks]

Check PPVRTC, 32KHz from U1900 pin 12? SMC_ADAPTER_EN, DSW_PWRGD present?

 

[pws6074]

Duke, i found a corrosion on Pin 4 ( PPVOUT_S0_KBDBKLT ) J9515, so i removed.
Right now, i get my 5v back.
So, i tested PPVOUT_S0_KBDBKLT PIN 4-3 short to ground, for see if i get some, and then the multimiter shows me 2.4 Ω.
So i start remove the component one by one, but i still get 2.4.

Any ideia?
Thank you for all your help

 

[dukefawks]

Usually in the KBD keyboard connector or in the board in that area. Is the board Chiming and working again, KBD backlight is not critical of course. Can take out D7720 to isolate the short and have the rest of the machine work.

 

[pws6074]

I did that, but still

 

[dukefawks]

Still what? Does the machine even boot now?

 

[pws6074]

The board works now. However, the system can't recognize the battery. I try another battery and i get the same thing.
I try to fix without ask you guys, but i'm stuck on this.
Any hint?

Thank you