Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

[Blacktek]

hi guys, this macbook it was working fine til i replaced the keyboard, after i put it back together it started beeping 3 times, and no video, it goes on endlessly.

Schematic and boardview attached.

C7332 is getting 12.5v, but nothing coming out of Q7330.. please help.

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

3 beep means memory ram. remove and put one ram module at once.

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

i did, multiple times, tried different memories even, but still beeping

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

remove q7330 and report voltage on pin 1-2-3-4-5

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

remove q7330 and report voltage on pin 1-2-3-4-5

removed mosfet: pins 1-4 0volts, pin 5 has 12.5 V

I've been tracing rails that produce 1.5v and notice that R2801 Has 3.3 on 1 side and 0 volts on the other side, it has the correct value which is 100k.
.

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

u7300 voltages ?

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

u7300 voltages ?

pin 1-5= 0.0v
pin 6= 1.8v
pin 7= 0.0v
pin 8 = 1.5v
pin 9-10= 0.0v
pin 11= 0.080v
pin 12= 5.0v
pin 13-14= 1.5v
pin 15= 6.5
pin 16-17= 3.3v
pin 18= 0.70v
pin 19= 0.0v
pin 20=0.080v

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

check if pin 4 and 5 of q7335 is shorted, if yes replace q7335

if pin 4-5 no shorted replace u7300

edit: voltage on l7330 without any ram module ?

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

check if pin 4 and 5 of q7335 is shorted, if yes replace q7335

if pin 4-5 no shorted replace u7300

edit: voltage on l7330 without any ram module ?

Q7335 not shorted.
Measurement of u7300 where without ram.

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

ok then try to replace u7300

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

ok then try to replace u7300

ok thanks friend i'll try to find another one of these bad boys.
is this chip responsible for creating 1.5v?

is it safe to make a jumper from pin 8 on u7300 to q7335?

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

wait: pin 4 of q7330 (after removed) has 0 volt, but pin 14 has 1.5 volt.... check c7325

if u can try this first before replacing u7300.

no dont do that jumper wire.

u7300 got enable signal from pin 16, but power good is not ok.

this chip create 1.5 volt for ram memory.

ps: pin 4 of q7330 has 0 volt after u removed it ?

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

wait: pin 4 of q7330 (after removed) has 0 volt, but pin 14 has 1.5 volt.... check c7325

if u can try this first before replacing u7300.

no dont do that jumper wire.

u7300 got enable signal from pin 16, but power good is not ok.

this chip create 1.5 volt for ram memory.

ps: pin 4 of q7330 has 0 volt after u removed it ?

C7325 is ok, not shorted.

Q7330 has 12.5v on pin 5, Pins 1-4 has 0v, whether is on or off the board.

I noticed resistor 2801 has 3.3v on 1 side and 0v on the other side, which is supposed to be 1.5v..Does this has anything to do with the memory not being recognized?

[dellxps15]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

circuit about r2801 also generate ddrvtt_en that is present on pin 17 of q7330

edit: volt on R2810 both side.

is pch getting extremely hot ? if yes could also be a bad nb chip.

[Blacktek]

Re: Macoook Pro A1278 3 Beeps, Missing 1.5v rail voltage please help 820-3115-B..

circuit about r2801 also generate ddrvtt_en that is present on pin 17 of q7330

edit: volt on R2810 both side.

is pch getting extremely hot ? if yes could also be a bad nb chip.

Nothing is getting overheated. R2810 has 3.3 on 1 side and 0.0v on the other side.