820-4924 S4 state no power on

No-Clean

Member
Ok first of all I fixed my 2nd board today on my own, following the power rails I found out S5 was missing, that one was easy since all I had to replace was a filter and done.

This other board 820-4924 is in S4 state, both C7185 and R7185 were a little corroded so I replaced them, still no power, PS is showing 0.012a steady and nothing gets hot, U1900 has PP3V42_G3H in pin 13 and pin 1 also gets 3.42v but all else is missing, I don't know why I got stock there and don't know where to go.
 

2informaticos

Administrator
Staff member
Post exact voltage for PPBUS_G3H and PP3V42_G3H.
Be sure to use original 60/85W Magsafe 2 charger. Do you get orange light?
Check SMC_RESET_L, 3V3_S5/SUS, PM_RSMRST_L, AVREF_SMC.
Try to start in SMC bypass mode.
 

No-Clean

Member
Some more relevant info:

PPBUS_G3H 12.26v
PP3V42_G3H 3.44v
PPVRTC_G3H 3.39v
PP5V_S5 0v

U7501 gets 12v in via pin 23 pin 29 0v, pin 25 0.238, pin 26 0.138
 

No-Clean

Member
Original charger with no adapter, no orange light, only green steady light.

How to SMC bypass mode?
 
Last edited:

2informaticos

Administrator
Staff member
"SMC_RESET_L 0.413v"
This explain all actual symptoms.

Post U5110 voltages.
Post resistance to ground on pins 5 & 8.
 

No-Clean

Member
U5510

pin 1 3.412v, pin 2 0v, pin 3 3.412v, pin 4 2.811v
pin 5 0.586v, pin 6 3.40v, pin 7 3.40v, pin 8 3.38

Resistance to ground on pin 5 17.15k, pin 8 356.5k
 

2informaticos

Administrator
Staff member
If R5100 is OK, remove U5110 and check again SMC_RESET_L.
If now OK, change U5110.
If still low, remove R 7100; if OK, change U7100.
J6100 can pull down SMC_RESET_L, if corroded.
SMC is the last option...
 

No-Clean

Member
OK replaced U5110 with SN0903049 I dont have a donor for SN0903048 I hope that one works, also replaced U7100,
SMC_RESET_L is now 1.48v but no fan spin :(
 

No-Clean

Member
Thanks my bad, I did not follow your instructions properly, when I remove U5110
SMC_RESET_L goes a little down to 0.597v but it doens come up to 3.42v
 

No-Clean

Member
J6100 is spotless, I also double checked and all else is good, what is standard practice to replace SMC, do people buy them already programmed or do people buy the programming machine, sorry I ma clueless here, also if the recommendation is to buy it programmed is there a good place to do so?
 

2informaticos

Administrator
Staff member
I recommend to reball it first.
Also you can try a reflow, using quality flux.
Heat until 180-200 degrees, just to burn eventually crap underneath.

To change it, need one from donor board, same 4924 model.
 

No-Clean

Member
Reflowing the SMC fixed the
SMC_RESET_L
problem and it is now 3.4v, I now get a orange light in the charger but no fan spin, PP5V_S5 is a little low at 4.75v, PP5V_S3 missing
 
Top