820-00928 Pulsing

donnos

Member
i'm getting 20V on usb and board is pulsing voltage everywhere

No all_sys_Pwrgd. but found pp1v2_s3, followed by missing PM_MEMVTT_EN <- is this the en signal for pp1v2_s3? and would this be the cause for pulsing?

also PP3V3_S4SW_SNS missing also due to SMC_SENSOR_PWR_EN missing. which should i look into first?

btw smc bypass does not work
 

2informaticos

Administrator
Staff member
PM_MEMVTT_EN enables VTT memory voltage, not 1V2_S3.

Do you note voltage pulsing any 3-5s seconds, or how?
CPU core voltage tries to appear?
PPBUS_G3H and 3V3_S5 pulsing too?
 

donnos

Member
The thing is.. No shorts can be found, nothing showing up on thermal cam. Measured all coils found good reading
 

2informaticos

Administrator
Staff member
Nothing gets hot in power cycle.
Apart of 3V3_S5, do you note voltage pulse on other big coil?
You should check for short and pulse after Power FETs too (page 74).

Also, test the board alone on the desk; nothing connected apart of USB-C charger.
 

donnos

Member
page 74 power FETs
pp3v3_sus = constant 3.3v
pp3v3_s4 = pulsing 3+v no shorts
pp3v3_s0 = pulsing 3+v no shorts
pp5v_s4 = barely pulsing, no shorts
pp5v_s0 = 0v no pulse no shorts
pp1v8_s4 = 1.8v Pulsing no shorts
pp1v8_sus = long pulse at about 1s intervals no shorts
pp1v8_s3 = Pulsing no shorts
pp1v8_s0 = Pulsing no shorts
pp1v2_s3 = 0V no pulse no shorts
PP3V3_S0_LEFT= 3v Pulsing no shorts
pp1v0_sus =long pulse at about 1s intervals no shorts
pp1v0_s3 = Pulsing no shorts
pp1v0_s0w = Pulsing no shorts

so i swapped u8209 and it powered up, i left it for about 2 weeks waiting for the customer to collect it, and its dead again. this time i reflowed U8209 again and it booted up again.

now i'm worried about returning the macbook to customer. C7607 C7605 is the culprit?
 

2informaticos

Administrator
Staff member
Be sure to get good solders at U8209.
Apply leaded solder on the board pads first.

Pretty sure, C7605/07 are not involved in the problem.
 

donnos

Member
revisiting this again as unit came back with the same issue. thinking might be the chip issue so replaced it, verifies that it booted and left on shelve for few days. Still same it doesn't boot now unless i put heat on that area. Can i jump pp5vs4 to pp5vs0 straight removing the chip?
 

donnos

Member
yeah. the point is to remove that chip to omit it from list of cause.
i don't see any other IC nearby that might have caused issue with pp5vs0. when issue happens i have pp5vs4 and pp5vs0_en but just no pp5vs0 output from u8209.

*edit* boot is booting normally now after a few days returning to customer first.
 
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donnos

Member
so this board is back on my table again, and due to the same cause. but this time, nothing i do can get pp5v_s0 back up again.

i have pulsing pp5v_s4 and also p5vs0_en but no pp5v_s0 output. i have tried replacing 3 chips and non of them worked.
I tried injecting 5v into ppv5v_s0 and board boots normally, surprisingly if i disconnect the voltage injection, board stays on and i get 5v on pp5v_s0, but of course does not boot when i restart.

i can't bypass the chip by shorting cause during sleep mode so it actually causes the fan to max spin in sleep mode(cause in sleep mode s4 rail is active), though this works if i want to get the mac to boot.

help!
 

donnos

Member
ntg, PS get stuck at 5v and no response after that,

so i tried ejecting 3.5v on pp5v_s4 and p5vs0_en both at the same time, and i'm able to get 3.5v output on pp5v_s0, which means chip is working. there must be something else causing dropping power. thinking might be 5v sense line.
 
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2informaticos

Administrator
Staff member
You may have a problem on U5630/70 areas.
Inspect their solders, traces and related resistors.

Does it start if LCD assembly is disconnected?
 

2informaticos

Administrator
Staff member
An Isense, or Vsense issue, should be bypassed starting in SMC bypass mode.

Any corrosion sign, or liquid spill history?
 

donnos

Member
so smc bypass is, remove battery, hold on power button and plug in charger? is that right even for type c models?

and board is totally clean. no liquid spill. no small corrosions as well
 

donnos

Member
Does not work... Holding down the power button the board Just stays at 5v until I let go, it just starts normal boot sequence(pulsing)
 
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