820-4924 green and orange light, but not booting

acehobojoe

New member
Hey guys

g3h rails are present, s5 rails are present, but checking pp5v_S4, it is missing. The enable signal seems to come from the SMC. I hope this board is recoverable. Thank you for any tips.

I have done SMC bypass mode and I actually get a chime, I just don't get any image whatsoever. Not sure about the mechanics of it. Vcore at 1.3 is present in SMC bypass but not present in normal boot.



Perhaps it needs a new SMC or a reflow
 

2informaticos

Administrator
Staff member
If stays on, check all SMC sensors level.
Starting on SMC bypass makes SMC not reading the sensors, but theyr values will be same as in normal mode.
See which one is bad.
 

acehobojoe

New member
Ok, I’ll check through the sensors. I’m sure that there is one with a shorted cap somewhere or the like. This board had a bit of water damage in 3 places but all of them looked fine when I checked for shorts. I’m sure if I check the smc sensor lines one of them will be part of the water damaged area.
I assume smc is needed for the computer to produce image anyway
 

acehobojoe

New member
s0_BKLT is near the damage on the LCD connector, I checked it and am getting 20 ohms of resistance. That seems a bit low.
 

acehobojoe

New member
We can mark this one as solved!! I had not confirmed that this machine just didn't have backlight. These newer ones don't fanspin when connecting power.

This one probably was booting but telling me it needed to charge the battery. Now with that backlight fixed we are good.

I injected power into S0 backlight and was able to see 1 amp drawn with just 2v at one capacitor on the back of the board. I guess I'll replace it now. :D
 

2informaticos

Administrator
Staff member
Yeah, this board spins the fan when gets heat, not on the start.

"checking pp5v_S4, it is missing."
But it doesn't start in this condition...
 

acehobojoe

New member
Well I think what happened was like I told you it wasn’t necessarily starting because it was probably doing that battery low thing. When I got it to start smc bypass it would have been present probably.
So it never was booting because of the “no battery” but then with backlight I can see that and it boots fine.

should I repeal and replace this 2.2uF 100v capacitor? It seems redundant. There are about 20 others on the circuit and I don’t think it’s super necessary. I took it off, but I’m not sure if I can find one in my old MacBook Pro donors

EDIT: found a nice big 2.2uF cap on an old MacBook Pro. It is big, but it works.
 
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