820-3437-b

[Aaron]

Hi,

Machine won't turn on/display, Board has short fan spins, magsafe light is orange.

- C1910 Was corroded, so I replaced it and ran a jumper (picture)
- PPVRTC - Voltage is low. Has 3.42, but has drops on the line to about 2
- Voltage at C1910 is 3.42


What other information can I get for you?

I have working board the exact same here to help trouble shoot

Thank you

 

[JohnB8812]

That looks no fun did you replace U1900? Also, are PP3v42 and PPBUS stable?

 

[Aaron]

- PPBUSG3H - 8.58 with drops to 8
- PP3v42 - 3.42V consistent
- C1910 - 3.33-3.42 (moves around)
- Pin 1 on U1900 (PPVRTC_G3H) - 3.33-3.42 (moves around)
- Pin 13 on U1900 (PPBUS_G3H) - 3.42

U1900 has not been replaced

 

[dukefawks]

So it is power cycling. Check if CPU Vcore is pulsing too at L7310.

 

[Aaron]

L7310 is 1.7V then drops to 0

Thanks Duke

 

[dukefawks]

The usual suspects apply: U1900, U1950, U6100 area termination resistors and traces, J6100, crap under SMC.

 

[Aaron]

Thanks Duke,

I removed U1900 and found this (Picture). Not sure if the tear is a big deal. Will continue by replacing U1900

 

[dukefawks]

Doesn't look dramatic, all pads are still there at least.

 

[Aaron]

Thanks Duke

- The fan has spun up to full a few times while sitting on the desk.

- pm_slp_s4l is pulsing as is S5l

- CPU heat sink is getting real hot

- U1900 has been replaced now, no change

- I checked around "U1900

, U1950, U6100 area termination resistors and traces, J6100, crap under SMC"

I will proceed by double checking these areas. Any other suggestions?​

Thank you

 

[Aaron]

Another clue...

When I first plug it in, I get no fan spin. If I plug it in again, then I get short fan spins

(All measurements previously were taken with short fan spins)

I decided to measure the rails when there's no fan spin. I get S5 rails, but no S4.
Also Missing:
- S4_pwr_en
- PM_slp_S5_L
- SMC_S4_WakeSRC_EN

Sorry for the confusion

 

[dukefawks]

CPU getting real hot is NOT good. Resistance to GND on Vcore?

 

[Aaron]

116 Ohms

Excuse the ignorance, does that mean anything?

 

[Aaron]

I found 3 solder balls just below the cpu at C1031 - is this a done deal?

 

[dukefawks]

116 is fine. U1950 pin 8 checked for corrosion and possible corrosion under SMC?

 

[Aaron]

Thank you.

Duke I found blue corrosion on the line to Q8150 (Photo), Replaced Q8150, nothing changed

WIll follow your instructions