A1708 820-00840 no power

[nassih]

hello everybody my macbook a1708 is giving me some issues:
no power and no amp consumption i have replaced c7078 was shorted to ground. voltage checked :
ppbus_g3h=0.3
ppdcin_g3h_chr_r=5.1v
ppvin_g3h_p3v3 g3h=3.8v
pm_en_p3v3_g3h_r=4.6v
pp3v3_g3h_vr=2.2v (required 3.3v)
pp3v3_g3h=2.2v (required 3.3v)
no short to ground
tanks

[mon2]

Re: A1708 820-00840 no power

ppbus_g3h=0.3

STOP.

Remove the fuse @ F7000. Then, meter in DC volts mode (30V or higher is ok).

Red meter probe to F7000, pin # 1 (ISL side) PCB pad.
Black meter probe to ground (shield is ok).

What is the voltage to ground ?

Next, meter in RESISTANCE mode. Remove all power.

Check the resistance to ground of F7000, pin # 2 (downstream / consumer side) PCB pad.

One meter probe on F7000, pin # 2 PCB pad.
Other meter probe to ground.

What is the resistance to ground ? Make a note of the meter scale if it is not automatic scaling.

Post your readings. From the very low voltage, sounds like you have a shorted capacitor on the downstream / consumer side of the logic board.

[nassih]

Re: A1708 820-00840 no power

tanks sir for reply.ok I will do all that tonight, I also want to inform you that after replancement of diode D6905 the voltages have changed:
ppdcin_g3h_chr_r= 20v
pp3v3_g3h_vr= 3.4v
pp3v3_g3h= 3.4v
ppbus_g3h=0.3

[nassih]

Re: A1708 820-00840 no power

voltage on F7000 pin 1 = 0.123v
when I was measuring the voltage across f 7000, I noticed that f 7000 has a high resistance about 470k,replaced from donor board same issue

[mon2]

Re: A1708 820-00840 no power

Do you have F7000 removed or on the board ?

The fuse must be removed to check if the PPBUS_G3H voltage rail is being generated.

[nassih]

Re: A1708 820-00840 no power

yes i have removed f7000 but still no generate voltage
how much voltage should be on f7000 when removed?

[piernov]

Re: A1708 820-00840 no power

Bad dual diode and possibly resistor feeding PP3V3_G3H input as always.

[nassih]

Re: A1708 820-00840 no power

I believe that the diode seems good, I have checked with meter, the last one was open on point 1 and 3
ppbus_g3h can generate the voltage without battery in?

[mon2]

Re: A1708 820-00840 no power

ppbus_g3h can generate the voltage without battery in?

Yes. One leg of the dual diode is a feed from the battery.

Other leg of the dual diode is a feed from the external power adapter.

The diode will select the higher of the 2 sources to create the PPVIN_G3H_P3V3G3H.

This input feeds the regulator @ U6990.

Review the voltage to ground on each leg of D6905 (dual ANODE diode).

Next, check the voltage to ground of PP3V3_G3H @ L6995, pin # 2.

Post each measurement.

[nassih]

Re: A1708 820-00840 no power

the voltage on D6990:
pin1: 0,3V
pin2: 20V
pin3: 19
PP3V3_G3H on L6995: 0,23v

[nassih]

Re: A1708 820-00840 no power

sorry its D6905 not D6990

[mon2]

Re: A1708 820-00840 no power

So this rail is missing. This rail may have a shorted part on this leg.

Remove all power. Meter in resistance mode.

Measure the resistance to ground of L6995.

Post the resistance reading.

[nassih]

Re: A1708 820-00840 no power

black probe to ground red probe to L6995 :130k
red probe to ground black probe to L6995 :2.8k

[nassih]

Re: A1708 820-00840 no power

voltage on L9695 : 3.4v

[mon2]

Re: A1708 820-00840 no power

From post # 10

PP3V3_G3H on L6995: 0,23v

Which is correct ?

[nassih]

Re: A1708 820-00840 no power

sorry PP3V3_G3H is 3.4v

[mon2]

Re: A1708 820-00840 no power

the voltage on D6990:
pin1: 0,3V
pin2: 20V

So PPBUS_G3H is now @ 20V ?


Can you confirm this? What changed ?

[nassih]

Re: A1708 820-00840 no power

checking resistance between PPBUS_G3H and the output of buck converters:
L8030: 1m
L8060: 0.8m
L7960:
L7900:
L7730: 1.5m
L7690: 15m
L7670: 12m
L7430: 8m
L7370: 7m
L7220: 6m

[nassih]

Re: A1708 820-00840 no power

So PPBUS_G3H is now @ 20V ?


Can you confirm this? What changed ?

no sir PPBUS_G3H is 0.037v

[nassih]

Re: A1708 820-00840 no power

to confirm:
PPDCIN_G3H_CHGR_R : 20v(pin2 D6905)
PPBUS_G3H_R : 0.037v (pin1 D6905)
PPVIN_G3H_P3V3G3H :19.76v (pin3 D6905)