A1708 all voltage ok but no power

[dclass-pro]

Hi guys, I have a macbook A1708 with mainboard 820-00840-A in which I have all the voltages, 3V 5V 1V etc... and when I connect it to the power supply it goes from 5V to 20V but starts with a 600mA absorption and then goes down and stops at 300mA... what can I check?
On the L7030 I have 13V everything seems correct but the macbook does not start.
Can you help me?

[mon2]

https://www.badcaps.net/forum/troubl...60-uf260/page2

Post # 30.

If this fails, need the requested details for the measurements.

[mon2]

What is the exact voltage to ground of PPBUS_G3H @ F7000 (check both sides)? Is it stable?

What is the voltage to ground of ALL_SYS_PWRGD?

Usually, if there is a peak current draw as you are observing, there is a shorted part onboard. Suggest to remove all power, meter in resistance mode. Measure the resistance to ground of each inductor onboard. Each inductor is linked to a power rail so the shorted rail will reveal itself in this investigation.

[dclass-pro]

On F7000 I have 13V stable
on ALL_SYS_PWRGD I have 3.2V
Between all the inductors and ground I do not have a low impedance except on those of the processor L7410 4.7ohm
L8410 6 KOHM
L8060 183 OHM
L7900 112 OHM
L8030 600 OHM
L7960 74 OHM
L7370 14 OHM
L7220 9.6 OHM
L7210 9.6 OHM
L7670 53 KOHM

[mon2]

Looks ok and ALL_SYS_PWRGD indicates that each monitored rail is OK.

Suggest to reflash with a known good bios. Check the BIOS forum. Backup the original before reflashing. If needed, can post one from my database.

[dclass-pro]

I tried to rewrite the bios but when I turn on the mac I only have a current draw of 187 mA, I saved the original, which I attach here in the post, but now even if I put the original back it draws 187mA and it doesn't start up like before

[mon2]

Will need voltage measurements.

What is the exact voltage to ground of PPBUS_G3H @ F7000 (check both sides)? Is it stable?

What is the voltage to ground of ALL_SYS_PWRGD?

what is the voltage and current draw on the usb c meter?

Is the current measurement fixed and spikes immediately to this value or climbs to this value?

Power cycling or stuck at this stage on power up?

[dclass-pro]

I tried writing again and now it works again, but always the same absorption, that is, after 40sec 300mA, can you send me your bios and I'll try?

[mon2]

https://www.badcaps.net/forum/troubl...60-uf260/page2

Post # 30.

If this fails, need the requested details for the measurements.

[dclass-pro]

I installed this bios and it finally started working 100% again THANK YOU!!!

[dbuergi]

Hello,

before i start a new thread i ask here because i want to empty my workbench. Had the same problem and CPU core voltage was at constant 0,96V.
I reflowed U7100 and put flux under the CPU at 200c hot air. Later the MacBook came back to life with question mark folder. Since the SSD was empty i wanted to install iOS today. MacBook started to boot with fanspin but stopped after some time and i got my 0,96v again without drop.
Any ideas what to do or should i repeat my steps and take U7100 off and clean the pads instead of only reflowing?

[dbuergi]

Update, its not U7100. Again heating the CPU with flux helped to make the MacBook run for 30 minutes until it freezed and stopped working.
Is it possible to use more heat to do a reflow? Only have done this to older Mac Pro 2012. I have also a small heating plate.