(347) 552-2258 [email protected]

820-3330-B - no power, green magsafe.

Atomrepair

Atomrepair

Member
This macbook was dropped by the owner; it has a green magsafe but wont power on. no fan spin
Measurements:

S5 rails are present, S3 and up aren't

SMC_RESET_L - present

SMC_BATLOW - 0V, no pulse when shorting SMC_ONOFF_L and not shorted
SMC_PM_G2_EN - present

PM_SUS_EN - 0V.

Unless I'm mistaken here, U7940 requires SMC_BATLOW to be present before it'll put out PM_SUS_EN

If thats right, then what is required for SMC_BATLOW to be generated by the SMC? I'm thinking the SMC cracked a trace/ball during the fall but I'd like to be more certain (if possible) before replacing the damn thing.
 
2informaticos

2informaticos

Administrator
Staff member
Dropped machine is a nightmare always.
Missing SMC_BATLOW can be sign of incorrect charger; be sure to use original 85W one.
In your case I think about broken trace/solder under SMC, or PCH.

Test all RTC signals (page 16) and also check basic signals for System Power Management (page 17).
 
Atomrepair

Atomrepair

Member
Shitbrain at work here... I was using a 60 watt charger. Doh.. This thing has been at another repair guy, it came with U8900 and U7400 missing from the board. I replaced those and then did the testing with the wrong adapter... With the right adapter, its working almost fine. Dont know why the other repair guy took the IC's off.

Two issues remained: cardreader didnt work because of a broken trace in the board somewhere, fixed that with a jumper.
There was a crack in the board at one USB port. I fixed all connections across the break with jumpers, making it work normally with usb 2 sticks.
However, USB 3 sticks are not detected most of the time and dont work properly when they are detected. I went over the cracked connections three times now, but everything is in order. I followed the rails across the board and found no problem, but cant check whats under the PCH.
The other port is functional with usb 3 sticks, but the macbook will hang on a black screen if left on for a little while. When booting from internal drive, this doesnt happen..
 
2informaticos

2informaticos

Administrator
Staff member
Which USB port doesn't work at all (as USB3)?
Check the small coils and capacitors corresponding to USB3 data lines (USB3_EXTx_).
 
Atomrepair

Atomrepair

Member
Port B (J4700) wont work with usb 3. I've already done the coils, will see if I can find anything else on those rails tomorrow.
 
Atomrepair

Atomrepair

Member
Made an error in my previous reply; Port B (bad one) is J4600

Think I found it...

USB3_EXTA_TX_P = 41.4kOhm / 0.352 diode
USB3_EXTA_TX_N = 41.4kOhm / 0.352 diode

USB3_EXTB_TX_P = 0L / 0L diode
USB3_EXTB_TX_N = 0L / 0L diode

These all go right to the PCH. So, either cracked balls under PCH or broken traces in the board. I dont see any test points or other spots these lines go to, so no way to jumper. As is this is near a crack on the board, I dont think its the PCH. Its actually operating stable from internal drive, so semi-fixed. Anything else to do before I call this one finished?
 
You must log in or register to reply here.
Top