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[SOLVED]820-3115 no cpu vcore

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roy.ruan

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logic board is 820-3115, getting all the power except CPUVCORE.

checked resistance to ground on r7515,shorted to ground. replaced the CPU IC , no short anymore,getting about 0.600 sth.
check r7441 (Since it's where the spilled was at) , it was 30 O, replaced and get 10 O.

power on but nothing change. checked Vron is there 3.3v. pin 46 29 16 all getting power. r7401 is fine.

then i replaced mosfet q7520 q7510 ,still no change.

don't know where to go now. any help please?
 
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roy.ruan

New member
FIXED!!! i removed the r7441 on the good board to check . found pin 1 was close to 0 and pin 2 is not reading. that means the pull down to 0 is from pin 1 not pin 2.
so pin1 is from the IC so , thought should be the IC, (that's actually the third one i replaced already) but anyway,i replaced another one. STILL DIDN'T GET CLOSE TO 0,
damn , then i was trying to get the schematics of MAX15119 and see the internal design and see why it's giving out 600 sth instead of 0. not available online.
i think once the chip is on , that pin should be pulled down. so I just jump a wire from GND to pin1 , pulled down that pin1 . damn then it worked!! now doing ASD on it

(I'm talking about pin1 and pin 2 of r7441,not the MAX IC)
 
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dukefawks

Administrator
You have now messed up the sense circuit for Vcore. If you want to ground anything it should be pin 2 of R7441, grounding pin 2 on U7400 directly may have unexpected effects.
Pin 2 of R7441 should go to the "local" voltage sense on the CPU and will be pretty much a short to GND
 
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roy.ruan

New member
But i removed r7441 on two good boards to check, after i remove r7441, pin2 is not 0V in diod mode, but pin 1 is, so I thought the "short to ground" side should be from U7400. that's why i grounded there.
I ran it the whole afternoon and no errors in ASD and OS running.
 
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