A1502, 820-3476 No light on charger, no boot

[adigon]

Hi there,

I've got my old macbook that i'm trying to fix. Had water damage, didn't work for a while, replaced battery, still didn't boot. After a few months picked it up again, it booted without AirPort card, so ultrasoniced that and it worked. Then the battery was empty and since it hasn't been able to boot up, no green light or anything. I'm suspecting U7090? I don't have a microsolder set up but I do have good enough probes to get voltages and resistances on key places.

Here's my current list of voltages;

PP3V42_G3H: 2.3V(no short, resistance to ground 135k)
PPBUS_G3H: sub 1v- changes, is at 0.6V right now, no short (resistance around 160K)
ADAPTER_SENSE: not present
SMC_ACOK: not present
PP3V42G3H_FB: 1.2V
U7090 pin8: 16.16V
D7005: pin 3 16.15V

with the _FB voltage being lower then the PP3V42 output, directly measured at the pin, I'm suspecting a chip failure? Visible corrosion at U5110 too, so maybe that's an issue

[piernov]

Re: A1502, 820-3476 No light on charger, no boot

1.2V on feedback pin of PP3V42_G3H regulator sounds mostly fine. Check the feedback resistors.
Corrosion on U5110 will be an issue as well.

[adigon]

Re: A1502, 820-3476 No light on charger, no boot

with the feedback resistorts you mean R7095 and R7096? Just check the voltage on them or? I don't have a microscope but they don't look in particularily amazing state, very hard to get a resistance reading on them too. Could they be the source of the trouble?