Macbook 13" A1278 2009 (K24) No power

[sylver]

Hi electronics gurus
For the first time I'm trying to repair a Macbook logic board
No green light on charger (just a very low alternative light switching between green and orange), SMC bypass not working. No sign of life whatever I do ! System is also not doing anything when trying to start it from a known good and fully charged battery !
I got schematics and brd and I started to look for the issue !
What I've seen when the magsafe power is connected is :
- Fuse F6905 is OK
- G3Hot is OK (3,44V)
- Q7001 pins 1/2/3 are 0V (instead of 16.44v as measured on another board) ! After checking, it appears that it is shorted with ground ... What I've also seen is that U7060 output is 0v (instead of 14.36V as measured on another board).
- Q7000 almost OK (pins 1/2/3 : 16,97V, pin 4 : 15,44V but pin 5 which is connected to pin 5 of Q7001 is -0.06V instead of 16,97V)

At this point it is not clear to me where I should check to continue progress ! Could anyone help me to understand what could be the issue ?
Check page 59 of attached document to find schematics related to my issue
Thanks !

[dellxps15]

Re: Macbook 13" A1278 2009 (K24) No power

voltage on u7000 ?

pin4 of q7000 must be low .... lower then 15volt to open good fets. generally 5-7volt.

first check u7000. ill focus here my looking.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Hi,
thanks for your answer !
Pin 5 (ACIN) of U7000 is 3,95V not sure if it's OK ?
I've found that C7020/C7021/C7022/C7023/C7027 capacitors (parallel mounted) are grounded (O ohm to ground) ... Maybe one of them is dead ? I guess that I have to remove them to check them, but before doing that I'd like experts point of view ...

About pin4 of q7000, I have a working board (a little bit different as it's a late 2008 and not a mid 2009) and when there is no battery plugged (not tested with battery plugged) I have the same voltage on pin4 of Q7000 !

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Ok I removed C7020 that was actually the problem ! At least a part of the problem !
Now the Macbook is booting from battery but not yet from magsafe (led is now low intensity green)!
I'll try to find a replacement capacitor and see how it's working once replaced

Could anyone help me to find the reference of this capacitor ?
It's one with 22 1E97 written on it, the data sheet gives :

C7020
22UF
20%
25V POLY-TANT CASE-D2-SM

[BCConnectionLLC]

Re: Macbook 13" A1278 2009 (K24) No power

Check the One wire part. You are either missing 3.42V or ACOK (3.3V) since it wont boot from Charger Id say you have a U7000 issue where ACOK is made.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Thanks for the advice, I'll check this part of the board for sure ! I received a replacement chip for u7000 so if I need to replace it, it will be done quickly
Regarding the capacitor I have to replace, I think that it's the package is "EIA 7343-20 (Kemet V, AVX Y) : 7.3 mm x 4.3 mm x 2.0 mm".
I just have to find some of them online now

[dellxps15]

Re: Macbook 13" A1278 2009 (K24) No power

check again pin 4 of u7000 as it must be 4 volt.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Ok I checked 1-wire output at U6901 level :
- IN/A & IN/B (Pin 1&2) are 0V (which are SMC_BC_ACOK signal)
- VCC (Pin 5) is 3.4V
- OUT Y (Pin 4) is 0V
So it confirms that U7000 is KO ?

dellxps15 : you mean pin 4 of Q7000 I guess, it's still 15.4V (with or without battery plugged) ...
It's time to change U7000, right ?

[dellxps15]

Re: Macbook 13" A1278 2009 (K24) No power

post u7000 voltage.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

I did quick check for U7000 (Magsafe & battery plugged) :
- Pin 1 (AGATE) -> 15.4v
- Pin 2 (CHGR_DCIN) -> 0v
- Pin 3 (ACIN) -> 3.99v
- Pin 4 is NC (VREF)
- Pin 5 (ICOMP) -> 0v
- Pin 6 (AGND) -> 0v
- Pin 7 (VCOMP) -> 0v
- Pin 8 (CHGR_VNEG) -> 0v
- Pin 12 (VHST) -> 3.40v
- Pin 16 (BGATE) -> 4.14v
- Pin 19 (VDD) -> 0v
- Pin 20 (VDDP) -> 0v

[BCConnectionLLC]

Re: Macbook 13" A1278 2009 (K24) No power

Pretty sure CHRG_DCIN should be the voltage that the main power rail coming in reads. Around 16V-18V.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

You're right, on a working motherboard I have 16.55V for CHRG_DCIN !
VDD & VDDC are supposed to be 4V also ...
I measure 96kohms between VDDP & ground on a working board, on the broken board I measure 0 ohm ...

[dellxps15]

Re: Macbook 13" A1278 2009 (K24) No power

check if l7000 is shorted.
check if q7020 q7021 are shorted.

if not remove u7000 and see if pin 2 voltage comes.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Q7021 seems to be shorted (between pins 1/2/3 & 5, I have 42 ohms in both ways)
How to check L7000 ? It seems to be 0ohm, but I have the same when checking L9701/L7400/L7401 ... I not sure my multimeter is very precise (I'll test with a better one tomorrow if needed) ...
I've ordered a replacement chip for Q7021 (RJK0305DPB), I'll have to wait to receive it to check if it solves all issues ...
Thanks a lot for your help

[Agent24]

Re: Macbook 13" A1278 2009 (K24) No power

Inductors will show a very low DC resistance normally. If you get no reading, or it is very high, then the inductor is open-circuit or otherwise bad.

You have to check actual inductance and\or do a ring test to ensure the inductor has no shorted turns. But likely they are OK.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Ok thanks for your answer, I did compare with L7000 on a working logic board and it shows the same very low resistance !
I'll keep the thread updated when I'll get the Q7021 replacement chip

[dellxps15]

Re: Macbook 13" A1278 2009 (K24) No power

put multimeter in diode mode to measure short, not ohms. if u have a good multimeter, 000 001 is short otherwise not. remove q7021 and check again pins.

remember to check pin 2 of u7000 too. probably both u7000 and q7021 are bad.

[BCConnectionLLC]

Re: Macbook 13" A1278 2009 (K24) No power

Id replace U7000 and go from there.

[sylver]

Re: Macbook 13" A1278 2009 (K24) No power

Thanks guys,
I tested q7021 with a good multimeter with diode test mode and it is definitely dead !
So I removed q7021 and now the light of on the magsafe is turning bright green !
I didn't try to turn on the macbook from magsafe or to plug the battery at the same time yet ...

[dellxps15]

Re: Macbook 13" A1278 2009 (K24) No power

q7021 supply 12.5 volt, so without it pc wont power on.

but green light means pc is almost alive