Macbook Air A2337 dead at 5V/0,00A

[mon2]

Well...not to be a 'Debbie Downer' but read this thread:

https://boards.rossmanngroup.com/thr...0-02016.64508/

Not a positive outcome but still worth a try I would say.

[Patrick501]

thanks for the link. I might give it a try.

Do you know if the DFU mode is only possible when the S2 rails are present since it wasn't possible for me to get into DFU by a second Macbook?

[mon2]

You are pretty much in the same boat as one of the iMacs we are still attempting to service. That is, we too could not use DFU due to missing power rails. The short answer is that the target SOC flash must be removed -> soldered onto a suitable PCB so that this flash memory device can be reflashed.

Requirements are:

1) need a suitable adapter for this rather strange shape and pinout
2) programming tool
3) firmware for this target logic board

The dump is posted inside a commercial ($$) device - u-bos2. You should have seen the stares I was given while roaming over HK and Shenzhen in October for this unit. I went to hunt down Master Liu of YT fame and missed finding his store in Shenzhen. I did not announce I was coming so it was an adventure. So much synergy for electronics in Shenzhen at this area of the city. They were selling tape & reel parts like a variety store sells candies at the street level. I have his full contact details now and plan to meet him next year but he stated for our iMAC unit, I can borrow the flash device or contents from any T2 unit. After this process, the DFU process will work to further update the logic board to a working status. He was very kind of his support. Cannot say the same for the others who did not waste even 15 seconds to look down and said, 'bring it in for service and our techs will tell you the cost'. Most did not have a clue of the complexity of the task at hand. Very few speak a word of English. Much like my knowledge of the Chinese language.

Only if it makes sense to do so, you could source a donor locked but working board for cheap? Then remove this same SOC and apply onto your board to see if the S2 and other rails start to function. I know there are a number of u-bos2 owners on this forum and I did make a few attempts to reach out for help for a dump of this flash but they did not. Will remember this for future.

Continue to post your progress. Interesting repair case.

[Patrick501]

Unfortunately, I couldn't find a cheap similar board.. But if I find someone around here with an adapter, I will try to flash the firmware tho. Since it's not my own macbook, I'm not gonna spent 200 bucks on the adapter for this one time job which might not have a positive outcome.
I hate to give up on repairs, so that's probably why I'm still on it. I recently had a macbook where repair wiki said it was a no-fix and I almost send it back to the customer.. It's working now...

[mon2]

I recently had a macbook where repair wiki said it was a no-fix and I almost send it back to the customer.. It's working now...

Nice! You should document this case and better yet, update the repair wiki with the details. I need to do the same for a few cases including an audio amplifier we repaired. The factory was useless. No reply at all (Genesis?). Will flame the vendor after posting the case. In summary, this audio amplifier had 2 x blown bulk caps that created the bipolar power supply + the ST audio amplifier IC was also damaged.

Yes, the u-bos2 tool is ~$400 (locally) which has the gadgets to work with this flash device. I will soon attempt a similar fix for this high end iMac from the local university. Will update you and this thread with the status. There are some vendors on ebay we found that will ship pre-flashed devices but not inexpensive. One out of France was ~$60 to us in Canada. Based on this store and again Master Liu - this SOC is a root cause of failures for the power rails. You can find low cost adapters on Aliexpress for < $10. SMD to PDIP.

Like this one:

(do confirm with a datasheet for the exact part onboard yours before ordering)

https://www.aliexpress.com/item/1005...6f9e18020Y1tUs

[piernov]

You don't need a $400 tool to flash an SPI ROM though… Dumps may have been posted already, otherwise use the appropriate forum subsection for the request.

[Patrick501]

I have a question before I start trying to do this.
Does it even make sense when there's no VCC voltage at the U1970?

[mon2]

No. This rail is linked to PP1V8_S2 (BUCK3) on the PMU @ U8100.

What is the resistance to ground of PP1V8_S2?

Would you have a thermal camera? Is U8100 heating up more than normal? U8100 may indeed be defective.

[Patrick501]

What is the resistance to ground of PP1V8_S2?

120K / 0.357V diode

Would you have a thermal camera? Is U8100 heating up more than normal? U8100 may indeed be defective.

I checked it again. The U8100 not heating up.

[mon2]

Review this thread (if not done already):

https://boards.rossmanngroup.com/thr...no-boot.64113/

[mon2]

Found a good page on M1 notebooks:

https://logi.wiki/index.php/M1_MacBooks

[Patrick501]

damn, good one mon2 ...PP5V_BSTLQ_VOUT_MPMU is 0 ohms
and the L8300 is a cap instead of an inductor. That's weird.

EDIT: I turned the brightness a bit down. The color of it is slightly different. It's an inductor but I measure14K. There's definitely something wrong

[mon2]

Good. Some progress.

No the inductor looks like a capacitor and is ok since you have 3v8. Leave that one alone (George Thorogood - Bad to the bone).

The 5v rail at 0v is of concern.

Would you have a dc power supply that can be dialed up to 1 volt?

If yes, inject onto this missing 5 volt rail. The shorted part will heat up like mad. 1 volt setting only!!

[Patrick501]

I have 3.8V going into the inductor but around 0.3V coming out. It should have a very low resistance but 14K is far away from being an inductor.
I just removed the cap which became hot. Now I have 20 ohms instead of nothing..

[mon2]

My bad. Expected this PMU to be the regulator. Flux and remove this part. It will need to be replaced because the component was pushed beyond normal specs. Correct that the resistance should be ~0 ohms. I was considering that this is a buck regulator and the 3v8 is the output. Instead it is in the input. Technically, you could bridge this inductor for testing but that is up to you.

[Patrick501]

I replaced the inductor by a wire. The PP5V_BSTLQ_VOUT_MPMU has 3.7V (instead of 5V) now and the U8100 is heating up.
To me, it seems like it has an intern short. The other caps are ok. I desoldered them to check but still 20ohms.
Only a bad cap would've been too easy...

[piernov]

The correct inductor is necessary for a boost converter to work, can't be replaced by a wire… Will likely damage the regulator too since it's gonna basically short full current to ground.

[Patrick501]

Same thing with the right inductor. So the U8100 needs to be replaced.