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what is good ripple free bench power supply... also which one is better for our use switching power supply or linear one? thanks

820-2979 board, fan spin regular speed, there is cpu-vcore.... do not not boot.. thats led white light (right by the hd) keeps on when press power button ...noting on scree. with external screen noting on the screen too... any help

board turn on now.... fan spin regular speed, no doooooooong or it does not boot... even with external monitor no video..... when i turns it on front led of mac keep on.... sorry about my bad English

with the battery ... it has constant ppbus

r7005 is 20 ohm, put new isl still sale problem !!! any help from any one ?????????

remove lvds cable then connect with external screen ... and see if there any thing on screen ....

i already remove , F7040, thats the first thing i did, also chk resistance, open line between c7020 and c7050,... resistance between 2 pic c7020 is 20 ohm, c7050 3 ohm

if you chk the video, you will see what is ppbus doing https://www.youtube.com/watch?v=OlUh_lpu_bI

last 2 hrs working on it no luck... still same, ppbus getting 12v stay there 3 sec then it goes down to5v and come back again,, also i notice r7086 pin goes to 6v stay 2 sec, then goes back to 15v

isl pin 27 and 28 getting 16.11v, , ...

got this board, 12.6 goes down to 6 then goes back again,

wow thanks for posting

wow i had 2nd board, that is fixed too!!!! i use caps from a 2013 donner mac air board. high quality caps....newer too.... i think when gpu need high power (when play game etc) from that power rail ... caps cant hold too much power and gpu turned off whole system.... if we put more powerful...

wow change c9560, problem gone, but duke what exactly science behind this ! could you place explain, thanks

not yet ... should i change it ?

hi duke is it might be gpu issue, if not, then what do i chk except c9560, thanks

louis is it GPU? do they gpu issue in 820-2850? if not gpu what do i check ? thanks

when c9560, is bad it produce some resistance and we get 1.3 v and problem.. in my case, its 1.5v which is perfect

c9560 is 1.5v thu

820-2850 board , some time it shut down it self or ... if you play game it will shut down.... is it any CAPS no good?