820-2879-b magsafe blinking green and orange light in turn

[Yoel Ren]

Hi, this is my first post here, thanks for having me in this group ^^
I have a 820-2879-b that was using a cheap knockoff battery, the magsafe light goes green and orange in turn repeatedly
tried replacing u7000, u6990, r5091, c7695, c7695. now the magsafe doesnt light at all

ppbus before replacing anything 1.5v
now : 0v

any idea where to check ?

 

[2informaticos]

Welcome to the group.

First post diode mode (red probe at ground) on F7040.
Also post voltages for U7000; pins 1, 2, 3, 12, 13, 9, 14, 15, 19, 20.
And exact resistance between pins 17/18 and 27/28 (NOT to ground).
Do you get 3V42_G3H?

 

[Yoel Ren]

f7040 : 0.44

if the read is 0.11 mv should i just say it 0v ? regardless of that, I will post the exact reading to be sure
U7000
pin 1 : not stable, 0.500-100mv
2 : 16.5v
3 : 3.9v
12 and 13 : 0 v
9 : 035.5 mv
14 : 0.39 mv
15 : 180-200mv
19 & 20 : 5v

resistance between 17 and 28 is 0, does it mean something is shorted?
and no pp3v42_g3h

 

[2informaticos]

Nothing moves on the board without 3V42.
However, you should have 12.2V on PPBUS_G3H.

For the moment must get 3V42.
Start checking diode mode to ground at L6995.
If OK, check R6905 and post U6990 voltages.

 

[Yoel Ren]

Hi, sorry for not updating, so I have pp3v42, I have smc_Bc_Acok too, sys_onewire is 0.7v, but still no green light at the charger

 

[2informaticos]

Please, post accurate information.
If you have 3V42, then pin 12/U7000 must have the same voltage!

"I have smc_Bc_Acok too"
"14 : 0.39 mv"
Doesn't look like you have it.

Re-post all U7000 basic voltages.
Check if SMC_RESET_L is present.

 

[Yoel Ren]

okay my bad, Im not focused..
U7000
pin 1 : 14.9v
pin 2 : 16.4v
pin 3 : 3.94v
pin 12 : 3.4v
pin 13 : 3.4v
pin 9 : 0v
pin 14 : 1.69v
pin 15: 0v
pin 19: 5.07v
pin 20: 5.07v

smc_reset_l is present at 3.4v

 

[2informaticos]

Post exact value (ohm scale, measured onboard) for R7080/81 and R7085/86.

 

[Yoel Ren]

Here is the value :
R7080 : 98.6 khom
R7085 : 0.472 Mohm

 

[2informaticos]

And the other two resistors?

 

[Yoel Ren]

my bad, I thought by /, I can just write one

R7080 : 98.6 kOhm
R7081 : 63 kOhm
R7085 : 0.472 Mohm
R7086 : 337.4 kOhm

 

[2informaticos]

Values look good, so Q7080/85 should be OK.
I hope you measured the resistors onboard.

You also didn't post resistance between pins 17/18 and 27/28.
"resistance between 17 and 28 is 0"
In such case, Q7030 is shorted.
Be sure C7025 is OK.

 

[Yoel Ren]

honestly, Idk what measuring onboard mean, I just probe the resistor on each end, is that right ?

so the resistance between 27/28 is 20.7 ohm
resistance between 17/18 is 0
tried replacing c7025, then the resistance between 17/28 become 3.6 ohm

 

[2informaticos]

"resistance between 17/28 become 3.6 ohm"
That means Q7030 is shorted.

 

[Yoel Ren]

so yeah I check the q7030 is shorted, and just to play it safe, i replace q7035 too.., now there's no short, but resistance between 17 and 18 still 3.5 ohm..

 

[2informaticos]

"17 and 18 still 3.5 ohm.."
What do you expect, from schematic???

Do you get voltage at F7040 now?

 

[Yoel Ren]

yeah i get 12.6v, but it always drop to 3.3v, then back at 12.6v, and drop again, cycling..

 

[Yoel Ren]

with battery plugged in, the voltage is steady at 12v,

 

[Yoel Ren]

I don't have pp3v3_s5, I checked at u7840, the pp3v3_s5_en is pulsing too

 

[2informaticos]

SMC detects a problem and cycles the power.
Check if other big coils pulse too.
Be sure no short on any secondary supply.
Also try to start in SMC bypass.