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820-00165 No fan spin - Pulses nearly everywhere

nik1981

nik1981

Member
Yet another 820-00165 and this one came from a bent mac air.

Looks like its only bent down the SMC end so hopefully not another dead CPU

PPBUS_G3H = sits at 8.59v and drops to 8.3v every 2 seconds

PP3v42_G3H = 3.42v stable

PP5V_S5 = 5v pulses
PP3v3_S5 = 3.3v pulses
SMC_PM_G2_EN = 3.3v pulses
PPVRTC_G3H = 3.34-3.37v pulses
PP3v3_SUS = 1.1v pulses
PM_DSW_PWRGD = 3.3v pulses
S5_PWRGD = 3.3v pulses
PPBUS_S5_HS_COMPUTING_ISNS = sits at 8.59v and drops to 8.3v every 2 seconds

PM_SLP_S4 = 0.1v pulses
PP3v3_s4 = 1v pulses
PP5v_s4 = 5v pulses

could it be an issue with PP3v3_S4 as its only pulsing to 1v? its over 5mohm to ground

PPVCC_S0_CPU = 0.00v
 
nik1981

nik1981

Member
Not bent too bad, no enough to break the screen even.

Possibly bent enough to break a connection under the SMC, which I have replaced but still get the same symptoms. CPU VCORE from Pin 1 of C1031 to ground is 10.4ohms
 
TCRScircuit

TCRScircuit

Super Moderator
Staff member
This will be fun. The fact PPBUS is going down probably means too much current draw on something. It could be literally anything
 
nik1981

nik1981

Member
Is there a way to narrow it down? Split it up a bit to see if it’s before or after something or is it just a case of look until your eyes bleed?

should I have a go at sticking 3.3v into PP3v3_S4 to see if anything warms up?
 
nik1981

nik1981

Member
Might be a dumb ass question but what is it saying by pulsing? Is it simply trying and seeing a fault, so shuts off and has another go again and again or is it missing something that causes everything after that to also pulse?
 
J

JohnB8812

New member
It's power cycling so rapidly turning on and off. I would advise try another BIOS for testing to see if power cycling subsides if not, this could be literally anything.
 
nik1981

nik1981

Member
Not another one only good for the parts drawer ?

Ill try another bios tomorrow just to see and possibly flux and reflow the entire left side of the board either side in case it’s something with a bad connection that might be impossible to spot. Maybe chuck it in the oven before totally giving up.

Cheers for the replies guys ?

The next one is another 00165 board too.. it’s all I seem to be repairing at the min
 
P

phuketmymac

New member
I am having the same issue with PPBUS on same board model.
Mine hasn't been bent but liquid damaged near SMC/Thunderbolt circuitry.

I've tried everything like replacing SMC, dumping Bios, replacing Bios chip, replacing U6101, checking for short on rails.
No real short but just 2 rails with a slightly lower voltage drop to ground.

I have been following those rails along to find out if I could find a short but none so far.
Rabbit hole + could be a dead CPU.

I have 2 820-00165 like this one. Power cycling both. Resistance to ground on CPU vcore is correct but still, CPU could be bad.
Nice to try and learn but time consuming and exhausting mentally...
 
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