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820-3115 ppbus low, not turning on

B

BCN_Techs

Member
Hi guys,

Got another 820-3115 logic board with this measurements:


PPBUS_G3H - 1,4 V seems to be shorted to ground but cant find where.
PPBUS_S5_HS_COMPUTING_ISNS - 1,4V
PPBUS_S5_HS_OTHER_ISNS - 1.4V
PPDCIN_G3H - 17V
PP3V42_G3H -3.42V
PPVRTC_G3H- 3.45V
PP3V3_S5 - 3.3
PP3V3_S5 - 0 V ( not shorted to ground)

Is it possible that all that is shorted to ground through CPU?



CPU is getting warm, even hot.
 
2informaticos

2informaticos

Administrator
Staff member
Not really short, as you get 1.4V.
But could have low resistance to ground; post exact value, diode mode and ohm mode too.

"CPU is getting warm, even hot."
This points to shorted high-side MOSFET from CPU power supply.
If you get close to 000 resistance between PPBUS_G3H and CPU coils, remove and check outside Q7510/20/30/50/60 (one by one).
 
B

BCN_Techs

Member
PPBUS in diode mode 0.004 and resistance 3.3Ohms


CPU coils u mean L7520/10/50 i guess. If so i get about 4-5 ohms between coils and ppbus-g3h
 
B

BCN_Techs

Member
L7550/10/20 to ground is 1,8ohms. and 0.002 in diode mode.

Other big coils (diode mode):

L7100 - 0.004
L7630 -0.008
 
B

BCN_Techs

Member
Yes. I was getting 0.5 between L7100 and PPBUS. So i replaced Q7100 and now getting 7 ohms ( still not turned on the board). IS that what i have to get? I checked resistance between theese two point on other board (820-3332) and getting over 3Khoms, But thats not working board so i cant take it as right one.


P.S: Pbus now is 2.6V but still seems to be shorted to ground. U7100 getting hot, changed it, now ppbus 3V but u7100 still getting hot.
 
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2informaticos

2informaticos

Administrator
Staff member
STOP to power a board where you clearly see a short!!!

Check resistance between PPBUS_G3H and all big coils.
Remove F7040 and post voltage and resistance to ground at L7030.
 
B

BCN_Techs

Member
Now i have another problem. No green light. Just put it in ultrasonic to clean all flux. Checked and R7085 is 33 ohms instead of 470Khoms. When remove Q7085 the value becames right. When put new Q7085 again 33ohms.
 
B

BCN_Techs

Member
Changed Q7085 now R7085 is ok, 470 kOhms. Still no green light.

Checked R7080/81/85/86 all is ok but seems that magsafe is blocked. ISL ohms between 17/18 and 27/28 are ok (20/4 Ohms)
 
2informaticos

2informaticos

Administrator
Staff member
Is F6905 OK?
Do you have voltage on it?
DCIN voltage pin 2/U7000?
Did you properly solder Q7085?
Check the same voltages using fake charger, or bench power supply...
 
B

BCN_Techs

Member
2informaticos said:
Is F6905 OK?
Do you have voltage on it?
DCIN voltage pin 2/U7000?
Did you properly solder Q7085?
Check the same voltages using fake charger, or bench power supply...
Click to expand...

F6905 is ok. No voltage on it. DCIN pin 2 on U7000 0V. With fake magsafe ( i dont have so i injected by power supplu) injected voltage on pin 2 and F6905 let pass voltage through.


Q7085 is soldered good.

I am stucked at this point. Seems to be current protection but cant find what is wrong
 
2informaticos

2informaticos

Administrator
Staff member
Original charger detects leakage and stops to power the board.

Post some voltages around U7000 with bench power supply.
Check if R7010/11 both OK.
Also check for short to ground at U7000 pins.

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

Please, do NOT quote an entire post visible few cm above; maintain the forum aesthetic...
 
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B

BCN_Techs

Member
U7000:

Pins:

1/2 - 4.2V
3 - 1.06V
4- 3,4 V
5 - 0 V
6 - 3,4V
7/8 - 0V
9 - 0.5V
10/11/12/13 - 3.4V
14/15/16 - 0V
17/18 -1.4V
19/20 - 4.4V
21 - 0V
23/24 -1.4V
25 - 4.4V
26/27/28 2,4V


I'm injecting 16V. U7100 is getting very hot.


R7011 3 9Khoms R7010 30Khoms so they are ok.

R7081 -62K R7080 - 99,5K R7086 - 317K

And R7085 - 77Ohms Removed Q7085 And it's now 470 as must be. Changed Q7085 by new one. Now R7085 is ok. Guess it was broken while injecting.


P.S. COnected magsafe and R7085 again 77ohms so Q7085 must be fucked again.
 
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2informaticos

2informaticos

Administrator
Staff member
"I'm injecting 16V. U7100 is getting very hot."
Change U7000 and Q7085 at same time.

Why did you inject 16V, and where???
 
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