820-3115 No light, but powers on

tlough75

Member
I have on the bench an 820-3115 that was originally working but had some corroded components around SMC area so I decided to clean up the areas and now the board turns on but no green/orange magsafe light. the other odd thing is PPBUS_G3H is 12.29V. But it is showing a blinking ? folder. I checked SYS_ONEWIRE and ADAPTER_SENSE, as well as SMC_BC_ACOK, all are present. I decided to reball the SMC because of local corrosion. I am reaching out because I am not sure what else to consider.
 

2informaticos

Administrator
Staff member
Did you try qanother DCIN board?
Check continuity from its central pin (Magsafe connector) to U6900.

Post diode mode to ground and voltage at SCL/SDA lines of battery bus.
If something strange, disconnect BIL and test again.
You may also need to remove D6950.
 

tlough75

Member
HI, yes I tried 3 known good DCIN's
We have continuity from pin 3 of DCIN connector and pin 2 of U6900
pin 4/ SCL: .536 (Diode) 3.48V
pin 6/ SDA: .534 (Diode) 3.48V
 

tlough75

Member
If it i helpful, this is what I have replaced thus far:
R5481
R5482
Q5480
C3896
C3897
C3898
C3891
and of course I reballed SMC...
 

tlough75

Member
Oh wow I didn't realize the fan is also stuck on high. I put the board in my test chassis to see if it turns on and it does. I looked at HW Monitor and the only thing it reports is HD temp.
 

tlough75

Member
Sorry, though you were asking to check continuity from the center pin of Magsafe connector to u6990. Must not understand what your were asking for.

Help me understand what removing D6950 does.
 

2informaticos

Administrator
Staff member
Pin 2 of U6900 is ground!!!
Do you really think I asked to check ground continuity?

D6950 should be good in your case; SCL/SDA lines look good...
 

2informaticos

Administrator
Staff member
Man, do you have continuity from central pin of Magsafe to pin 5 of U6900???
There could be a low value resistor in serie, nothing more (on DCIN board).
 

2informaticos

Administrator
Staff member
Is time to change SMC now.
Once removed, check continuity for SYS_ONEWIRE between U6900 and SMC pad.
If no good, repair the trace and reball original SMC.
 

2informaticos

Administrator
Staff member
Why do you like so much the ultrasound?
Maybe broken trace, because of hot spot, if you didn't use seep option.
Also could be knocked off component.
Which signals missing now?
 

piernov

Moderator
Staff member
Make sure it's completely dry and there are no random residue on the board. Often you just let it rest for a day or two and it comes back to life.
 

tlough75

Member
I used weep function on UC, only cleaned fpr 2 min. I'll check for broken traces. I UC'd cause I couldn't get all of the flux fout from under the SMC.
 

tlough75

Member
I used sweep function on UC, only cleaned for 2 min. I'll check for broken traces. I UC'd cause I couldn't get all of the flux out from under the SMC.
 

2informaticos

Administrator
Staff member
You should use small flux amount to resolder SMC.
And no need to clean it, if is good quality; do NOT use chinese honey!!!
 
Top