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820-2879 no sysonewire/pp3v42_g3h

Gmorb

Gmorb

Member
system will not power on no green light. i replaced r6929 and on occasion will get a very quick green light when re-plugging charger.

I connected a power supply to pp3v42_g3h sent its voltage and system powers on.
i can see u7000 is getting its proper vdd, vddp,chgr_dcin and acin voltages.
acock only outputs 1.2v, chgr_ugate 1.3v, chgr_phase 0.028v

u7000 bad?
 
smiba

smiba

New member
You need to have PP3V42_G3H before you can get SYS_ONEWIRE. U7000 is needed to get PP3V42_G3H though, as it needs to open the Q7080 gate.

Resistance to ground in Ohm on PP3V42_G3H? R6905 OK? PPDCIN_G3H_OR_PBUS voltage?

Looking good around U6990?
 
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Gmorb

Gmorb

Member
r6905 was shorted replaced it now i have pp3v43_g3h BUT! pp3v42_g3h is fluctuating between 3.2-3.4v on SMC_BC_ACOK and SMC_BC_ACOK_VCC
 
smiba

smiba

New member
R6905 can't be shorted, its supposed to be 1Ohm. (Its basically a cheap fuse and also part of an RC filter). I assume you meant broken?

PPBUS_G3H stable or also pulsing? If so, is it hitting (or getting very close to) its expected voltage of 12.6V?

PM_SLP_S4_L pulsing?
 
Gmorb

Gmorb

Member
ppbus_g3h is stable at 12.57v
no pulsing 0v on pm_slp_s4_l
resistance to ground on 3v42 is 0ohm
 
smiba

smiba

New member
Alright so lets activate the brain, 0Ohm to ground on 3V42 does not sound right

Inject voltage and find whats shorting out
 
Gmorb

Gmorb

Member
re measured

ppbus_g3h is 0.280v
no pulsing 0v on pm_slp_s4_l
resistance to ground on 3v42 is 0ohm
 
D

dukefawks

Administrator
This is all not making sense anymore and I bet something got fried. I have no idea what you did. You can inject 3V on 3V42 rail and see what heats up.
 
Gmorb

Gmorb

Member
all i did was replace 6905 and ultrasonic it after. the first measurements i gave were from the wrong board since im working on two of the same model machines. the machine is getting its 3v42 voltage and i get a green light 3v42_g3h is stable. PPDCIN_G3H_OR_PBUS and PPDCIN_G3H_OR_PBUS_R are not stable and fluctuate from 16v to 16.30v.

SMC_BC_ACOK and SMC_BC_ACOK_VCC also pulse from 3v to 3.4v

just to clarify pp3v42_g3h is stable my explanation on post 3 was incorrect.
 
Gmorb

Gmorb

Member
Resistance to GND on 3v42= 2.7 kohm
No corrosion around U7000
just realised it wont turn on when using the apple charger but when i use a power supply i get a fan spin and shuts down.
 
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Gmorb

Gmorb

Member
just realized it wont turn on when using the apple charger but when i use a power supply i get a fan spin and shuts down it takes some disconnecting and reconnecting of the power for it to stay at .26 amps and then it will turn on sometimes it stays on with no problems other times it shuts itself off.

bad mcp then?
 
D

dukefawks

Administrator
No idea about that specific behavior, but 2.7K on 3V42 is usually a dead MCP. Too much of a risk to waste time on this 8 year old crap then.
 
Gmorb

Gmorb

Member
Hmm well after fidling with the power on and off it stopped turning on but now i have a stable ppbus dcin and acok voltage. resistance to ground on 3v42 is 8.25kohm and i have a 3v s5 state and a 5v s5 only outputting 4.2v maybe something causing the voltage pulsing finally burned out?

update:wow i just realized c7291 is missing from the board.. was this thing powering on without it? Is that even possible?
 
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smiba

smiba

New member
Missing C7291 can cause this, but it also means someone decided it had to be gone. Place it back and keep your eyes open for other pulled components.

The system might be able to start without C7291 but PP5V_S3_REG will have a considerable amount of ripple and inaccuracies making the system unstable.
 
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