A1466 820-00165-A no power

[hgoncalves]

Hi,

I have an A1466 820-00165-A that has no power.

It tries to power on (goes to 350mA, and drops to 25mA), but doesn't power on.

The region arround U1950 was corroded and I ireplaced U1950 and R8167 but without success.

On U1950 I get 3.4V on PP3V42_G3H but 0V on ALL_SYS_PWRGD.

Can you help?

 

[2informaticos]

No pulse at all at ALL_SYS_PWRGD?
Remove Q8150 and check again.

 

[hgoncalves]

I get a pulse of 2.8V, but immediately drops to 0V

 

[2informaticos]

Pin 3 of U1950 pulse at same time?
If not, remove U1950 and check for corrosion.
If yes, check for pulse at PLT_RESET_L too.

 

[hgoncalves]

I have pulses on pin3 of U1950 and on PLT_RESET_L too.
I already replaced U1950, and cleaned the pads (no corrosion).

 

[2informaticos]

"Remove Q8150 and check again."
Did that?

Also try SMC bypass.
Check all SPI Bus Termination resistros and their traces; clean J6100 too.
Try known good BIOS.

 

[hgoncalves]

HI,

I did removed Q8150, but with the same result. Now I've soldered it again.
SMC bypass didn''t worked either.
All SPI Bus Termination resistors are ok.
J6100 is clean and with no corrosion.
With a clean ME BIOS, the same result.

 

[2informaticos]

Then probably bad CPU.
You can try heating it with quality flux; maybe just accumulated crap.

 

[hgoncalves]

OK, tks.
What temp and heat time do you recommend?

 

[2informaticos]

180-200 C degrees, no more than 15-20s...

 

[hgoncalves]

TKS!

 

[hgoncalves]

Before I heat the CPU (haven't done it yet), I took a look in the thermal cam, and the only thing that gets hot is the area arround U7100, and it seams that C7150 gets a bit hotter (not shorted and has 8,59V on both pins), and the U4650 area was a bit corroded (already cleaned it). Do you think that this mean something related with the problem?

 

[hgoncalves]

After heating the CPU and making an ultra-sound, now I don't get PP5V_S4RS3 (0V), but I have PP5_S5
Any idea?

 

[2informaticos]

Seems that you make use of UC more than needed.
At least test the boards before the process.

I suspect knocked off components, or broken trace.
Also possible CPU damaged, if overheated.

 

[hgoncalves]

Tks for the tip about UC. I've done it because of the CPU flux (I've used a lot).
I don't think that I've overheated the CPU (but not sure), and I can't see broken components.
Any idea of the major traces that I should look for?

 

[2informaticos]

Try reballing SMC, as last option...

 

[hgoncalves]

I've rebaled SMC but same result. It tries to power on (no fan spin), goes to 0.350mA, and drops to 0.25mA.

I have 0V on PP5V_S4RS3 and 0V on PP5V_S0.

On PP3V3_S5 I get 3.3V but on PP3V3_S4 I only get 0.324V.

Do you think that is the CPU?

 

[2informaticos]

Very likely bad PCH/CPU...

 

[hgoncalves]

OK. TKS.