mac a1286 - 820.2850a not turning on

[highpulse]

Well im not a big experienced on macs , so here it goes .

This one was gave from another store mentioning it turn on in 100 attemps(ex)
when i chek it , once i insert the magsafe connector , the led stay very very dim , not charging as well , since i don't notice the charging light not turning on as well .
really dont know much were to start , assuming could be some SMC problems for what i read around .
cheked that bios got the vcc of 3.30 volts on the usual pins 3 7 and 8

any help will be apreciated .

[highpulse]

Re: mac a1286 - 820.2850a not turning on

noone ??

[polytek]

Re: mac a1286 - 820.2850a not turning on

Hi, brother,
i will try to help you, you have to start on page 3 on the schematic diagram ,first check ac volatge is it correct, then the power good signal;

[dj_ricoh]

Re: mac a1286 - 820.2850a not turning on

dc in board maybe?

[highpulse]

Re: mac a1286 - 820.2850a not turning on

for what i notice i dont have 3.3 and 5 volts on the coils , alltough i got a ldo of 3.3 volts , since the bios is beeing feeded with the correct vcc.
even tryed to replace the tps 51125 but the same thing occured.

[highpulse]

Re: mac a1286 - 820.2850a not turning on

nop not powerboard , since i got 16 volts on the nmain board , and also got a big coil giving me 12 volts
so the main power is on the board ,

[dellxps15]

Re: mac a1286 - 820.2850a not turning on

could be smc problem. check smc in voltage, and if g3hot 3.42volt is present.

[highpulse]

Re: mac a1286 - 820.2850a not turning on

noticed that vin of 51125 its around 12.65 volts is that normal ª?

[highpulse]

Re: mac a1286 - 820.2850a not turning on

dellxps , usually there is a bypass pins for g3hot , can you help me out
?

[highpulse]

Re: mac a1286 - 820.2850a not turning on

also dont have this boardview to know were the components are exactly
i assume the SMC Ic is the one right near were the keyboard ribbon attach , right ?

[dellxps15]

Re: mac a1286 - 820.2850a not turning on

this notebook should get ati vga known to be defective, but if it doesnt power on, its not vga for now.

dont have schematic and board viw of that by now, but looking on some picture, pad should be on the right side.

check voltage on this 2 pad. (the 2 more bigger)

[highpulse]

Re: mac a1286 - 820.2850a not turning on

also PGOOD on tps51125 its 0 volts

[highpulse]

Re: mac a1286 - 820.2850a not turning on

well does 2 pins give me 0 volts

[dellxps15]

Re: mac a1286 - 820.2850a not turning on

if you have dim green light i suspect u dont have g3hot. locate g3hot regulator and measure it.
edit:

grab it from here:
http://forums.macrumors.com/showpost...postcount=2948 tnx to varungargi

[highpulse]

Re: mac a1286 - 820.2850a not turning on

DELLXPS If you notice on the photo you sent me , chek near the socket were the keyboard connects , there is a IC cy8c24794-24 right above this Ic there are 2 large pins , on one of does pads , i got the 3,41 volts .

[highpulse]

Re: mac a1286 - 820.2850a not turning on

there is a coil l6995 , and i got there 3.41 volts

[highpulse]

Re: mac a1286 - 820.2850a not turning on

ok new results i got the coil of 3.3 working , the main regulator coils , was under the speaker , just noticed now , and its giving me the 3.3 volts ,

now my doubt is wich is the SMC ic ? is it the one i mentioned right near the keyboard socket ? cy8c24794-24 ??

[dellxps15]

Re: mac a1286 - 820.2850a not turning on

here is the right place for smc bypass, but without green light and no 3.3 volt it wont start.

check u7000 voltage.
check f7040 if 12.5volt are present.
check l7260 for 3.3 volt.
check l6995 for 3.42 volt

always check both side of coils

[highpulse]

Re: mac a1286 - 820.2850a not turning on

all ok , what voltages you want from u7000 ?

[highpulse]

Re: mac a1286 - 820.2850a not turning on

like i mentioned the pads you showed in this picture is were i told i found 2 big pads and one of them got 3.42 volts