Macbook Pro A1989 820-00850 No Power

[rarinpear]

Hi all!

I have a Macbook A1989 820-00850 that completely died out of the blue.

I have used a usb tester and the computer is (not) drawing 5v 0amp.

I have now taken the board out and there are no visual clues of components going bad.


Can you help me diagnose the problem?

[mon2]

Carefully measure the voltage to ground @ F7000 - check both sides. If the voltage is not in a normal range, power down and configure the meter into RESISTANCE mode. Remove all power / no battery. Measure the resistance to ground on each side of the fuse F7000.

If the resistance to ground is low, carefully flux and remove F7000 fuse. Allow the board to cool and then measure the resistance to ground again on each side of the remove fuse PCB pads @ F7000.

Which side of the removed fuse is with a low resistance? Post each measurement.

[rarinpear]

The voltage on both of the F7000 sides cycles between 1.1 and 0.95 v.
Resistance to ground is 1 (infinite? measured with the 2M ohm setting of my multimeter).

should I remove f7000? this might take some time as I do not have a hot air station here

[mon2]

Suggest to use a lower resistance scale and measure this fuse again. Short your probes and you should read ~0 ohms. Measure the resistance to ground again at the fuse. If you read a '1' then the resistance is too high to measure and a higher meter scale should be used. Either way, you should have a lower resistance on this rail. At this time, you do not need to remove F7000 unless we can confirm there is a part that is shorted on this power rail.

Next, with the meter in DC volts mode (20v or higher), measure the voltage to ground of PPDCIN_G3H.

[rarinpear]

My multimeter does not have OL, it reads 1 instead. It reads 1 when measuring resistance to ground of F7000 (both sides), under all ranges (2M - 200).
Resistance on F7000 (probes on the two ends of F7000) is close to 0 (resistance of the cable).

The voltage to ground of PPDCIN_G3H is 5.16v, measured at the test point on the left of C8464.

[rarinpear]

Hi all!

Diagnosis (following repair.wiki and CD3215 Bootup Sequence):

PP3V3_UPC_**_LDO - 3V3, present, for all 4 CD3215s
PP1V8_UPC_**_LDOA - 1V8, present, for all 4 CD3215s
PP1V8_UPC_**_LDOD - 1V8, present, for all 4 CD3215s
PP1V1_UPC_**_LDO_BMC - Not Present, for all 4 CD3215s

is it an indication of a bad cd3215? Is it normal for me to observe PPDCIN_G3H (see my last reply)?

[mon2]

PP1V1_UPC_**_LDO_BMC ; should be present for the active USB port used to power the logic board. Remove all power and measure the resistance to ground of this rail. Also test in DIODE mode. With no power, red meter probe to ground; black meter probe to this LDO rail.

[mon2]

Sharing a diode chart for the inductors on this board. Remove all power. Meter in diode mode. Red probe to ground. Black probe to the inductor to test.

[rarinpear]

resistance to all PP1V1_UPC_**_LDO_BMC rails is 130k ohms.

Diode mode beeps for all inductors in groups 3 and 2 (L7220, L7210, L7410, L7420, L7430).

[mon2]

Yes, the low voltage rails will tone beep due to the very low resistance to ground on the respective tested rails. What about the other inductors on the board? Do their diode mode readings match the posted reference diagram?

[rarinpear]

Here are all the measurements in diode mode (red on ground):

Inductor: Expected - Actual

L9021: 273 - 320
L9020: 273 - 320
L9030: 349 - 295

L9080: 358 - 310
L9081: 358 - 310

L6900: 362 - 316
L6901: 362 - 316

LB700: 190 - 407

L8102: 28 - 130

L7270: 12 - 35

L8100: 116 - 199

L7220: 3 - 9
L7210: 3 - 9
L7410: 2 - 9
L7420: 2 - 9
L7430: 2 - 9

L7702: 56 - 70

L7600: 401 - 334
L7660: 413 - 348


F7000: 390 - 332

L7030: 472 - 385

L8410: 840 - 806

L3500: 217 - 412

[rarinpear]

I also checked and 5v are being fed to U7000 (isl9420), but then I get 0v on PP3V3_G3H, is that normal?

[mon2]

PP3V3_G3H is created by U7650. If it is 0 volts at the output then there could be an excessive current event on this rail and/or the ENABLE pin is not turning on this power rail.

Remove all power. Meter in resistance mode. Measure the resistance to ground of this power rail. What is the measurement? Checking for an out of the normal range resistance on this leg. If it is too low, there is a shorted part onboard.

[rarinpear]

Diode mode reads 350. I cannot measure resistance because it changes while I am reading it (it either keeps increasing or decreasing for reasons I do not understand).