820-3462-A no fan spin

Sinnlosvoll

New member
it worked but turned off after a really short while, took it apart, didn't see anything obvious, put it back together, booted once, no reaction since then.

Checked the voltages:
PPBUS_G3H: 12.5V
PPVIN_S5_HS_COMMUNICATION_ISNS: 12.5V
PPVIN_S5_OTHER_ISNS : 12.5V
PPDCIN_G3H: 16.9V
PP3V42_G3H: 3.40V
PPVRTC_G3H: 3.32V
PP5V_SUS: 5V
PP3V3_S5: 3.32V
PP18V5_DCIN_ISOL: 16.9V

So I assume there is a mismatch with the datasheet as it says for the DCIN buses it should be 18.5V? SInce the power supply also nominally has 16.5V (60W).

MagSafe2 light is green for about 2 seconds then turns amber.

What would be the next thing to check?
 

Sinnlosvoll

New member
Definetly no drop judging from the chassis but it seems as if someone has worked on it before. But the working for 20-40seconds -> not starting was from just to now.
The turn off was also not based on temp of the cpu, all I could verify.

Maybe i take it back about temps? Since I have just been probing some testpads around the smc and the PM_THRMTRIP_L is at 0V. I assume that means thermal protection and comes from the cpu, but the heatsink is on and cold.
 
Last edited:

dukefawks

Administrator
Oops 3462 and not 3476 board so no U1950. 3462 are the worst boards. Are you using a real 60 or 85W charger? The usual corrosion spot on these is around the SMC.
 

Sinnlosvoll

New member
3462 are the worst boards
Perfect to start then -.-

I would rate the charger genuine, the voltage without a macbook is about 0.4V but DCIN when connected was high enough so I assume it is powering up like it should.

Funny thing, when I plug it in initially the charger slightly buzzes until I hear a klick, then the green light comes on for 2 seconds then turns amber (naked board). The charger also buzzes like that when I accidentaly shorted the magsafe power pin to ground. Also 60W.

I would like to check some of the boot sequence Voltages. Can you give me a short rundown of what signals are important for startup and in which order?
 

dukefawks

Administrator
There is nothing more to check then you already did. Now you need to inspect where the corrosion was/is. Check charger on a working machine and see in system properties if it is recognized as 60W or 85W. This machine will not power on from a 45W charger and some chinese fakes.
 
Top