820-3437 PP5V_S5 pulsing from 0 to 5.

BCN_Techs

Member
Hi there,

Got mba with no liquid damage. Just stopped working. The macchine boots in SMS bypass and working fine but not booting normal way.

Magsafe led is always greeen. CHecked all main rails and except of PP5V_S5 are presents. PP5V is pulsing constantly.


Any idea?
 

2informaticos

Administrator
Staff member
"While U7501 wasn't on board"
Did you power on the board without U7501???
Check for short on L7520/60 now.

"The macchine boots in SMS bypass"
Some sensor blocks the SMC.
First check AVREF_SMC.
Next check SMC_DCIN/BMON_ISENSE and SMC_DCIN/PBUS_VSENSE.

Post exact PPBUS_G3H voltage and check resistance between pins 17/18 and 27/28 of ISL6259.
 

BCN_Techs

Member
"Did you power on the board without U7501???"
No, just plugged magsafe and light turned orange.

"Check for short on L7520/60 now"

Checked and not shorted.

AVREF_SMC 3,3V

SMC_DCIN_VSENSE pulsing 0-1,5V
SMC_DCIN_ISENSE - 0.03-0.06 V pulsing
BMON_ISENSE - pulsing to 0-1,2V
SMC_DCIN/PBUS_VSENSE. pulsing 0-0.03 every half second.

PPBUS is 8.62 and constantly goes down 8,5, pulsing too.

ISL6259

17/18 3.3
27/28 20 ( it was first i checked.)
 

2informaticos

Administrator
Staff member
"PPBUS is 8.62 and constantly goes down 8,5, pulsing too."
You didn't mention that before.
If board works with battery, then could be leakage on the input stage.

"No, just plugged magsafe and light turned orange."
3V3/5V MOSFETs got voltage, you've lucky nothing burnt.

"BMON_ISENSE - pulsing to 0-1,2V"
1.2V is high enough to block the SMC.
"17/18 3.3"
Did you check directly between U7100 pins?

Try fake charger, or lab power supply with 60/85W cable.
 

BCN_Techs

Member
with fake charger doesnt boot .

"Did you check directly between U7100 pins?"

Yes.


With battery connected PPBUS is pulsing 8.42-8.44 battery disconected 8.55-8.62. Doesnt boot with connected battery



"Yeah never ever apply power to a board without the TPS or bad things will ensue..."

Ok John, thanks for info


Any idea what can i do?
 

2informaticos

Administrator
Staff member
Must be other SMC sensor involved, if it always starts in SMC bypass.
Can also be SMC, if never gets orange light.
Did you test with correct Magsafe 2 charger?
Post exact voltage for PPBUS/PPDCIN_G3H.
 

BCN_Techs

Member
Tried new one. Now i have no green light and 8,18 PPBUS. Do you know if 980 YFC LM4FS1BH 5BB... (original that comes with board) can be replaced by 980 YFC LM4FS1AH 5BB ? Also in PDF says LM4FSXAH5BB
 

2informaticos

Administrator
Staff member
"Tried new one"
Really new???
Why did you buy that?
SMC has firmware, need to pick it from donor board, same model.
 
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