820-3662 charred points on dcin board short on PPBUS_G3H

grmacs

Member
Ok, so there was charred points on two inside points of charger input of DCIN board. I replaced DCIN, hooking mac charger up shuts the charger off. I have a short on PPBUS_G3H somewhere. Wasn't sure the best way to find the short without potentially blowing something important up like CPU or smc...
 

2informaticos

Administrator
Staff member
Looks to be happy case, you can inject voltage on PPBUS_G3H.
Start with 1V, maybe no need to reach 3V even.
Be sure to use a powerfull lab PSU; at least 10A limit.
 

2informaticos

Administrator
Staff member
Lift one side of the board and see where the short remains.
Inject voltage on that point.
If you discard 100% any shorted high-side MOSFET, you can inject higher voltage.
But with such low value, 3-5V should overheat something.
 

grmacs

Member
Things are working better. two issues. Blinking orange light on charger when battery is plugged in. Computer boots well but no backlight. Checked with external display to verify it boots to login.

I apparently have a short related to display connector as I get a short from pin 1 to ground diode j8300 when display is plugged in but I really find it hard to believe its the screen... I don't have another to test with. This was liquid damaged in area of j8300 and customer shorted plug dcin trying other chargers to see if it would turn on.
 

2informaticos

Administrator
Staff member
"I get a short from pin 1 to ground diode j8300 when display is plugged in but I really find it hard to believe its the screen"
I know people believing in god even without any reason; you have a powerfull one, at least...

Video cable, or display.
The short may also appear inside connector, only when the cable is inserted; change connector, if is the case.
 

grmacs

Member
Man. you were right... I was able to test on another display and short is in the display. Customer is willing to pay for new display for this. Unbelievable. $$$
 

grmacs

Member
Still have a charging issue. This boots fine. Runs off battery or MS2 but battery doesn't charge. I was getting a blinking orange light but replaced q7130. Orange light now stays on and sometimes display shows charging, sometimes it doesn't but battery status appearance doesn't change whether the MagSafe is plugged in or not and the percentage battery only goes down. I checked the resistors are correct readings at r7102 (missing and I believe this is normal? but resistance between those points is 75k), r7100 is 0 ohms & r7112 is just under 1k. Resistance between pins 17/18 is 2.9 ohms and 27/28 is 22 ohms
 

2informaticos

Administrator
Staff member
R7102 is not mounted; NO STUFF, as per schematic.

Exact PPBUS_G3H voltage w/ and w/o battery?
Did you try known good battery?
 

grmacs

Member
So... apparently now it is not operating off of Magsafe only. not sure when that changed. I only have 1.5V slowly drops toward 0 on ppbus_g3h without battery plugged in. with battery ppbus_g3h is 11.1V
 

2informaticos

Administrator
Staff member
You must fix PPBUS_G3H problem first, on charger only.
PPDCIN_G3H and 3V42_G3H stable?
 
Last edited:

grmacs

Member
PPDCIN_G3H is steady at16.54V
3V42_G3H does hold at 3.42V
I replaced q7130 again as diode test showed no connection no matter how I tried to read point to point. That now looks better but I still don't have fan spin on charger only... PPBUS_G3H is now 1.7V and slowly rising since changing q7130 again.
 

2informaticos

Administrator
Staff member
Do not expect fan spin with 1.7V at PPBUS_G3H.

Post basic voltages for ISL6259; pins 1, 2, 3, 9, 12, 13, 14, 15, 17, 19, 20, 27.
 

grmacs

Member
1-3.6mv
2-2.7V
3-.477V
9-0V
12-3.42V
13-3.39V
14-3.26V
15-48mV
17-.9mV
19-5.53V
20-5.53V
27-16.2V

resistance pins
17/18 2.9ohm
27/28 22 ohm
 
Last edited:
Top