Macbook Pro a1425 logic board

[DWalsh]

I am working on a late 2012 Macbook Pro a1425 I have the following with the board removed from the system and only the dc board attached.

Green light and then amber after a few seconds which means the PPV3v42 is working.

I measure the following
CHGR_DCIN = 16.5V
PPBUS_G3H = 1.3v
PPDCIN_G3H = 16.5V
PPDCIN_G3H_CHGR = 16.5V

R7020 + R7021 + R7022 = 10.03 ohms

CHGR_LGATE = switched output
CHGR_UGATE = switched output

looking for suggestions on where to go next.

Thanks.

 

[DWalsh]

Also there is no Fan spin

 

[2informaticos]

Is that 820-3462 board?

"R7020 + R7021 + R7022 = 10.03 ohms"
Is that reading between pins 27/28 of ISL6259?
Post value for 17/18 too.

Also check voltage for some pins of U7000, 2, 3, 12, 13, 19, 20, 9, 15.

 

[DWalsh]

I'm not sure where to find the 820 number, the board has 2 fans.

yes on the 10.03 ohms

reading between pins 17/18 on isl6259 = 10.44 ohms

readings on pins

2 = 16.25
3 = 3.95
12 = 3.41
13 = 3.37
19 = 5.48
20 = 5.49

9,15 I can't locate another place on the board to get readings on this and I don't have a probe small enough to get those.

 

[JohnB8812]

Resistance to ground on PPBUS_G3H?

 

[DWalsh]

8.8 ohms measured at r6905 to ground with power disconnected.

 

[2informaticos]

You didn't specify which pin of R6905.
Remove F7040 and see where the short remains.

"17/18 on isl6259 = 10.44 ohms"
You must get aprox 3 ohms there.

"yes on the 10.03 ohms"
And aprox 20 here; no idea how you measure on the board.

Take readings on the C7020/50 directly.

 

[JohnB8812]

You?re like measuring 17/18 and 27/28 improperly but we?ll worry about that soon. Remove F7040 and see if the short is on pin 1 or pin 2

 

[DWalsh]

the measurement for PPBUS_G3H was taken from pin 1 of R6905

This measurement
"R7020 + R7021 + R7022 = 10.03 ohms" was taken from pin 1 of R7021 to pin 1 of R7022 with the resistors in series 10 ohms + .02 ohms + 10 ohms = 10.02 ohms so my 10.03 ohms reading seems to be in tolerance.

"17/18 on isl6259 = 10.44 ohms" this was take from pin 1 of R7051 to pin 1 of r7052 the schematic shows R7051 as 2.2 ohms + R7050 .01 + R7052 as 0 (??) = 2.21 ohms I am reading 10.44 on a second reading of that I'm showing 10.63 now.

I will remove F7040 and check for the short and report back.

Thanks

 

[2informaticos]

"10 ohms + .02 ohms + 10 ohms = 10.02 ohms"
Really NOT; 20.02 ohms if you want be so exact.
With a reading of aprox 20 ohms is OK.

"17/18 on isl6259 = 10.44 ohms"
Now measure R7051/52 separatelly and change the one with higher value.

 

[DWalsh]

ha yea your right, what was I thinking?

what temp do you guys use for these boards to remove, I had mine set to 380c and was able to remove some components from a test board but this fuse doesn't seem to want to come loose?

 

[DWalsh]

I rechecked the reading at R7020 + R7021 + R7022 = 20.02 not sure what I did before.

 

[2informaticos]

Add first leaded solder on its terminals...

Temp adjust depend by every hot air station.
I use Mlink H1 at 475 degrees and 5 air flow.

 

[DWalsh]

Thanks the leaded solder did the trick!
R7051 + R7052 + R7050 = 3.3 OHMS now

short to ground now appears on pin 2 of the fuse F7040

 

[DWalsh]

measurement from pin 1 of R6905 to ground is 8.9 ohms pin 2 of R6905 to ground is 18.9 ohms

from the schematic I have there isn't anything between pin 2 of F7040 and pin 1 of R6905

 

[2informaticos]

Nothing more than the same name, =PPBUS_G3H; what do you think this mean?
Impossible to draw all the connections in the same page for a mainboard...

So you have aprox 9 ohms on PPBUS_G3H, which is main power rail.
Check now for a similar value on the big coils (secondary supplies).
If you get same value on any, check then resistance between that coil and PPBUS_G3H. A reading close to 0 ohm will mean the high-side MOSFET of respective power supply is shorted.
Do NOT inject tension into PPBUS_G3H before check all of them.

 

[DWalsh]

I removed F9700 and short remains
I had also removed R6905 I'm not sure If I had said that in the last post.

Checked the following TO PPBUS_G3H

L7030 P1 448.2 ohms
L7220 P1 2.93 k ohms
L7550 P1 12.3 ohms
L7560 P1 12.3 ohms
L7510 P1 14.5 ohms
L7520 P1 14.5 ohms
L7630 P1 25.2 ohms

I attached the power supply and I am now getting 12v at pin 1 of F4070 while its removed.

I guess the next suggestion will be to inject power and see what heats up?

Thanks

 

[2informaticos]

"I removed F9700"
???

"I guess the next suggestion will be to inject power and see what heats up?"
My next suggestion is to read again the previous post; but REALLY read it!

 

[JohnB8812]

If the short is on pin 2 of the fuse, it could be several things. Inject voltage at pin 2 start low around 1 volt to make sure it is not the CPU. Commonly, large caps can cause your short.

 

[2informaticos]

Do NOT inject tension before you check what I mentioned before.
NEVER ever inject voltage on the main power rail before discard a shorted high-side MOSFET!!!!!!!!!!!!!!!!!!!