A1502 820-3332-A no image

[hgoncalves]

Hi,

I have an 820-3332-A that has no greenlight, but the computer chimes, the fans start at full spin, and stays at full rpm, and has no image.
Already done SMC reset but with no sucess.

PPBUS_G3H = 12.25v
PP3V42_G3H = 3.4v
PP5V_S5 = 5v
PP3V3_S4 = 3.3v
PP1V8_S0 = 1.8v
PP1V5R1V35_S3 = 1.3v
PP3V3_S0GPU = 3.3v

It looks that i have an short on PPVCORE_S0_AXG because it has 0.8 ohms to ground and 0.0015v on diode mode

Can you help?

 

[2informaticos]

0.8 ohm is surely bad.
I hope you measured after 10-15s after power removed.
AXG voltage doesn't appear, unless high graphics load, but such a low value is not good.
Lift L7550/60 and see where the short remains.

You also have a SMC issue, as PPBUS_G3H is incorrect; missing Magsafe light too.
Solving SMC problem with bad CPU, may not be the best option to start.

 

[piernov]

Ivy Bridge always measure very low resistance to ground, iGPU power rail often between 1 and 2 ohms. If CPU is warm it can measure lower than 1 ohm.

 

[hgoncalves]

I measured it after a few minutes powered off.

Shell i remove L7550/60?

 

[2informaticos]

0.8 in ohm scale is not good; if you've measured correctly.
Compare with VCORE in ohm scale.

 

[hgoncalves]

Well, I'm not sure if i measured it correctly, but the fact is that now it has 1.2 ohm to ground.
PPVCORE_S0_CPU_PH2 1.1 ohm and 0.8V

 

[2informaticos]

These are better values; CPU can be good.

You should fix the PPBUS_G3H issue, which can be SMC related.
Check voltage and diode mode on SCL/SDA lines of battery bus.

 

[hgoncalves]

Sorry, but i'm having a problem identifying those...
I think the you mention the ADC_SDA / ADC_ SCL lines.
When looking for them i try to measure them on UD000 and on RD007, but those are missing on the board. Are they NO STUFF (not showing no stuff on my schematics) or are they missing from the board? Am i looking on the wrong place?

 

[2informaticos]

Look at J6950; you will probably understand what I meant...

 

[hgoncalves]

OK, now i understud

SMBUS_SMC_5_G3_SCL = 0.555 V on diode mode and 3.4V

SMBUS_SMC_5_G3_SDA = 0.545 V on diode mode and 3.4V

It looks ok to me. What should i check now?

R6950 it's ok (9.9 Kohm) but with 0V
D6950 = 3.4v on both pins

 

[2informaticos]

Difference in diode mode looks a bit high; check again...

 

[hgoncalves]

I changed the battery on my multimeter...

You're right.

SMBUS_SMC_5_G3_SCL = 0.555 V on diode mode

SMBUS_SMC_5_G3_SDA = 0.551 V on diode mode

 

[2informaticos]

Remove D6950, just in case.
You can also try changing U7000.
Let SMC as last option...