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I see oscilloscope is needed for getting into a higher level of success repair rate, just wondering what's the good one to start and where I can learn some practical usage of it. thanks

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.

but anyway,thanks a lot DUKE!!!without your suggestion,we wouldn't doubt that pin at the first place!!!

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...

thanks for the hint, i think i found the problem. pin 2 of r7441 to ground resistance is 670 sth. it's supposed to be close to 0 as i compare on the good board. that's why im not getting 7.7k between 2 and 3. not sure if pin2 of r7441 had been corroded in the layers, it's directly connected to...

pin1 and 48 are getting around 12V. resistance between pin2 and 3 is 5.83 M O

checked R7402 and R7403, both looking good, one is 150K one is close to 180k

you meant r7403?

R7402 and what?

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...

alright,thanks man

should i use the original SN or get another one? I do believe the guy previously was to unlock the machine due to a icloud lock i think. if i put back the original SN and connect to internet,it will be locked again right?

yea,that's the problem,the guy put random number or whatever,its' FFFFFFFFF,something like that, can't update online now for the new OS

having a Imac, got worked on by someone else before, the guy didn't do process right i guess and put a SN that didn't belong to the machine.and that made it having few problems now long story short, need the bios bin for 820-2301-a but can't find it anywhere, just want to see if anyone can help...

F7140 was blown, replaced it, PPBUS_G3H finally is 11.sth V! but MFG!still not turning on!! pp3v3 s5 is ready and present already. I think you can be right. maybe the CPU is dead already. just don't want to believe this shit since spent so much time on it.

so I found the shorted thing. previously resistance to GND on PPBUS and L7320 are both 0.004. I found nothing hot so eliminate the ICs and caps(usually they would be very hot if shorted) I took off the Q7310, that was the shorted thing even that area has no liquid spilled. I replaced Q7310 and...

tried another hour,really nothing at all. only things hot are the jumper wires(i would say they are a bit warm)

halo anyone has ideas or advice?

PSU limit is 5a. im getting around 3.sth A when i inject around 8v, if i go higher,still getting the same thing

hi guys, Im having a liquid spilled machine, took it off, not much spilled, little on keyboard connector,and touch pad connector, cleaned them off with ultrasonic, all look fine. started measuring everything and found that ppbus_g3h is shorted to ground. f7140 pin 1 i have normal around...