820-00045 troubleshooting steps

[arghhh]

Liquid damaged 820-00045, looks nasty especially around ISL95530 BGA chip. I'm using an original charger with it. The issue is PPDCIN_G3H is only 5v not 14.5v so it's not generating PPBUS_G3H properly I believe. However, it looks like U4780 is the chip that tells the charger to step the voltage up?

Please correct me if I'm looking at this wrong and where to go from here. I am using a new DC in jack and cable.

 

[aprendiz]

Where exactly are you measureing PPDCIN_G3H????

 

[arghhh]

F4700 10 char

 

[aprendiz]

Remove F4700 and see if you get PPDCIN_G3H.....

 

[arghhh]

Still 5v 10 char

 

[Imyk]

Do you have a solid green / orange light on the charger ?

 

[arghhh]

lol.......

12" retina guys

 

[Imyk]

Is there no light on the logic board where the D.C. In is at?

 

[dukefawks]

The system "talks" to the charger to enable the 15V output. If that does not work it will be stuck at 5V. The system should run off the 5V, 15V is only needed to fast charge the battery.

PP3V3_G3H present? It is generated by the 95530.

 

[arghhh]

PP3V3_G3H is 1.529v. The LED next to the battery connector is dimly lit though.

 

[arghhh]

PPBUS_G3H is 0v, 0.03v drop to ground. Probably short? Don't have a known good here to compare.

 

[dukefawks]

Yeah that's a short. U7100 still suspect or something around it.

 

[arghhh]

Would that explain why PP3V3_G3H is so low? Also, what signals does the ISL look for in order to turn on the LED?

 

[dukefawks]

ISL does not turn the LED on, look at how D6900 is powered.
There is a short on PPBUS, first find out where it comes from

 

[arghhh]

pp3v3r3v0_aon, which comes from the ISL, no?

 

[arghhh]

Ok so I removed F7140 and the short is on the system side (pin 2). However, when I measured voltage with on pin 1 with the fuse removed, i got -.18v -- is this because the SMC can't see PPBUS_G3H?

 

[dukefawks]

Dunno, first that short needs to be gone. Inject voltage and see what heats up.

 

[arghhh]

Ok I hooked PPBUS_G3H to the power supply and turned the power supply on, but it didn't draw any current. So I turned it off and measured again and the short had gone (.33v drop). WTF? So I put the fuse back and there still is no short to ground, but PPBUS_G3H is still 0v when I plug it into the charger... What is going on?

 

[dukefawks]

Uhm, dead U7100?

 

[arghhh]

I hope not, that chip is BGA and over $30 new. So if the chip is getting power on H3 and H7, and CHGR_ACIN is high, should I get SMC_BC_ACOK? I see a few pins that also look like enables, so not sure.