820-3115 bad smc?

[Kyle93]

Have a 820-3115 that has no liquid damage, it supposedly just suddenly died. currently no green light. I have replaced isl u7000 since I was getting 18V on pin 2 but 0v from pin 14. Same results.

here are some voltages

PP3V42_G3H 3.42v

PPBUS_G3H 12.40v

SMC_RESET_L 3.42V

SMC_PM_G2_EN 0V

Is this bad smc?

 

[2informaticos]

Check first power rails and signals for SMC (U4900 - 2 of 2), page 45.
You can try to reball it...

 

[JohnB8812]

I think it's more likely there is just crap under it as you have 12.4 volts. I'd say remove the edge bonding and run flux under it and heat it. That will clear out any crap under it, and I would bet solves the issue. Also, you could have a bad ISL/poorly soldered ISL, but fluxing the SMC is easiest to do first.

 

[Kyle93]

Replaced SMC with a known good SMC but still same results. There was no crap under old SMC either

PM_CLK32K_SUSCLK_R is only 0.15V, could this mean bad PCH?

 

[Kyle93]

Solved. R5010 needed replacing.

 

[2informaticos]

PCH requires 3V3SUS to send out PM_CLK32K_SUSCLK_R.

Post resistance to ground at SMC_PM_G2_EN (diode mode, red to ground).
Check voltages and signals for SMC (U4900 - 2 of 2) at page 45.

 

[Kyle93]

everything was working perfect including booting into OS but after going through the ultrasonic cleaner I have a dead board again.

ppbus_g3h only 0.690V

SMC_PM_G2_EN 0.434 resistance to ground

 

[2informaticos]

"after going through the ultrasonic cleaner I have a dead board again"
Do you have UC whitout sweep function, or don't use it?
Because I don't see other reason to damage the board...
Could be more dificil to fix the board now, than before.

Resistance to ground on PPBUS_G3H?
Post basic voltages for U7000.

 

[Paul Daniels]

Sometimes also you might not have driven out all the liquid from under the chips like the CPU/PCH . Make sure you put it through the distilled water flush + alcohol + low bake + cool off; a couple of times I've had boards not start up after being in USC that ended up being because I was impatient and didn't give the board a chance to properly dry off.

 

[Kyle93]

Resistance to ground PP3V42 0.768

Not sure if my UC has sweeper or not, I use the crest P500H Louis recommended on the youtube channel years ago. He never mentioned about a sweeper function.

pin 2 17.80V

pin 12 3.42v

pin 14 0v

Have short to ground ON SMC_TCK Resistor R5080 came off along with corroded pad in UC. Have tried jumper wire but still no luck. Short is there even without R5080. Is this unrepairable now?

 

[Kyle93]

Paul Daniels didn't know and have never used a oven after a board has come out of UC. What kind of oven is recommended? Toaster oven?? How hot and how long should a board go in after alcohol bath?

 

[2informaticos]

"short to ground ON SMC_TCK"
A resistor can never generate a short; unless is not covered by corrosion.
In fact R5080 is the pull-up resistor, doesn't even go to ground.
Your problem is underneath SMC, or SMC itself shorted.

 

[Kyle93]

with SMC off of the board I still have a short to ground of 0.000 on SMC_TCK

 

[2informaticos]

That means short inside board.
Follow the trace outside SMC and cut it off, trying to locate the part with short to ground.
Still possible to solve it, but not easy.
Very strange for a board without corrosion...

 

[JohnB8812]

Yeah and I think TCK is for programming the SMC so you don’t need it. Dig out the short if possible

 

[2informaticos]

I think SMC requires high level on TCK line for normal operating.
The signal is not used, but its level can be critical...