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820-3024.. Quarter turn w/ all S0 rails present before full absence

2andrewd

2andrewd

New member
Fan spins for a few seconds during which all S0 rails turn on but fall off after stopping. I've tried changing U2700, checked u7000 current sense's. What should I be looking for at this point in terms of ****_PWRGD signals etc. aside from the S0_Mains verified?

Questions:

1) When moving through voltage rails is one meant to check each associated "sub-rail"?
2) What is the proper voltage threshold for SMC_MANUAL_RST_L?
3) What is AXG core and why is it missing on functioning boards? What's the idea going on there?
 
A

aprendiz

Moderator
What is the history for this board, water damage, dropped??
First the first, ppbus_g3h stable and at what voltage, Do you have green light??
AXG is only present if internal display is present....
 
2andrewd

2andrewd

New member
No traces of liquid or corrosion. ppbus_g3h stable at 8.45v pp3v42 stable at 3.45v and green light present.
 
2andrewd

2andrewd

New member
I get a short blip on mouse led as it powers on.

Voltage to ground on
PPBUS_S5_HS_COMPUTING_ISNS .295 (.482 on working board)
 
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dukefawks

Administrator
Of course there is PP0V75 or there would be no fan spin...

Need history on the board, this usually does not just happen?

Vcore present on L7510 when fan spins?
 
2andrewd

2andrewd

New member
History is a guess aside from what I see which is lack of corrosion, no real discoloration of any probe points. Trace amounts of fruit punch(?) around the base of C7119 and C7120; highly likely was cleaned before falling into my lap. it arrived naked in a lot which contained several broken screens with beat up corners maybe pulled from one of them after the accident?

Yes - VCORE at L7510

L7330 v to ground .091
(.113 on working board)
 
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dukefawks

Administrator
If Vcore is present then it could really be anything. Inspect for corrosion and/or knocked off components. Could also possibly be a corrupt BIOS, but that is pretty much the last option.
 
2andrewd

2andrewd

New member
Bios no go and I may have ruined christmas.

I forgot that I borrowed R7012 and R7021 from U7400 CPUIMVP_FB and CPUIMVP_FBA. Plugged in and got full fan spin (huh?) without them but cpu vcore was gone. by the time i realized my mistake an put them back, quarter turn returned and now missing cpu vcore. I'm assuming I killed U7400 by running it without those resistors.. would that make sense?


IF... u7400 is dead, do i need to replace all mosfets along with it? I recall a video "why newbies suck at restoring vcore" stating replace everything together.
 
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dukefawks

Administrator
U7400 never dies, more likely the CPU fried because there was no feedback and Vcore spiked high voltage. Another trash board.
 
2andrewd

2andrewd

New member
Out of boredom/determination/sub-consious desire to waste time.?.? i circled back around to this one and it appears I mistakenly relayed inaccurate info.

CPU vcore IS indeed still present. Same symptoms, fan spins for 3 and stops without any signs of attempting to power cycle. during the 3 second spin up, I catch all S0 rails. I checked all u6100 termination resistors and traces which are good.

Changed out U2700 along with y2705 for lack of oscilloscope. Same response. I checked the end portion of the power on sequence as shown in the block diagram and found the following.

PLT_RERST_L 0.16 (Assuming this one is out of spec?)

CPUIMVP_VR_ON 3.3
PM_PCH_PWROK 3.3
CPU_PWRGD 1.05
PLT_RESET_L 3.3
PM_MEM_PWRGD 1.5
L7100 0.92
L7330 1.5
L7630 1.05
L7550 0.79
L7510 1.17

ALL_SYS_PWRGD 3.3

I apologize if the response remains the same as Duke's prognosis above but wanted to swing this back by with the updated info and a bit of optimism before calling the game.
 
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dukefawks

Administrator
All that doesn't change anything. Vcore is present and the board is brain dead it could be anything. As this is a board with unknown history that has been in a pile of crap the chances of some component knocked off/cracked resistor. Anything and everything is now suspect.
 
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