A1706 (820-00923-A) Stuck on 5V/30ma

[Jenzo]

Hey, working on an A1706 that doesn't power on anymore.

The usb-c amp meter reads 5V/30A. On the right side (XA & XB) the meter loops (on/off), on the left side it stays on. This might indicate something U2890 related?

PP3V3_G3H is present and stable, PPBUS_G3H sits at 50mv.

Any advice? Thanx in advance!

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Remove all power. Meter in resistance mode.

Measure the resistance to ground of PPBUS_G3H.

Post your measurement.

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Hey mon!

0.450 on pad 2 of the fuse, F7000

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

My bad, just noticed you said resistance mode.

Black probe on ground, 40.6k

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

The PPBUS_G3H resistance is not showing a short circuit. Both resistance and diode readings are fine.

Clue is here:

right side (XA & XB) the meter loops (on/off)

The CD3215 needs to be investigated. Each LDO rail on the ACE (CD3215) controllers needs to be checked.

This video details the same case as yours:

https://www.youtube.com/watch?v=vXAK2l1oMZM

Summary - the local ROM chip that is used by the non-working pair of CD3215 may be defective. Confirm no parts on this ROM chip are missing. If you are comfortable, swap the ROM from the working side to the non-working side to see if this fixes the fault. Lots of flux + low air pressure to carefully remove the ROM chip.

This might indicate something U2890 related?

Yes.

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

As far as I can tell no shorts indeed, nothing gets hot either.
The LDO lines seem to be fine.
Nothing is missing around the U2890 either.

The video you linked is actually exactly the same case, amazing. I'm fine with swapping the ROM chip (U2890), is this the UB090 on the other side? Just making sure

Also, I'm having trouble locating a replacement chip, any advice on this? Thanx for everything so far!

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

The exact chip is in stock at Digikey. The trick will be finding an adapter to program this part.

This package is the USON 2*3 mm size. Not very common.

There are bare pcbs you can buy on AliExpress for around $22 usd that note T2 adapter boards and are black in color.

With this board, you can solder in a blank flash chip and convert it to pdip for use with your programmer.

This flash is 3v3 version so no low voltage conversion is required.

The trick is in the very small package for programming.

The dump of this tbt rom I believe can be found in the bios section of this forum.

Suggest to buy a few of the blank chips. They are cheap on Digikey.

Reference:

W25Q80DVUXIE

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Additional question, now the customer tells me the problem started with the screen showing horizontal lines. I'm looking at the schematic, but I can't figure out if it could be related in any way. Should I assume it's the flexgate issue, and then followed by the ROM chip going bad? Seems like very bad luck to me then. :')

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

https://www.fixxo.in/blog/macbook-pr...016-2017-model

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Unlucky it happened so shortly after each other. It is what it is I guess.

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Customer is blaming you for this design flaw??

Show them the above link. Offer them perhaps a discounted labor rate to swap out the display but is certainly not related to your work. That is just abuse by your customer wanting a free lunch.

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Hey, sorry didn't see your last reply. The customer doesn't want to pin any display issues on me at all thank god, he was just kindly giving more info about what happened because he brought it in for "no power", but forgot to mention at first that a bit before it happened he had issues with the display.

By now I've replaced the UB090. It solved the looping/charging problem, but then a new problem came up. U8205 heated up, removed it and measured, PP3V3_S0 is shorted to ground. I tried injecting 1V/2.5A, but nothing gets hot really.

Any ideas?

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

If not done already, remove the display and remove the trackpad.

Remove all power -> meter in lowest resistance mode.

Measure the resistance to ground of PP3V3_S0 again.

Post the measurement.

[Jenzo]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Sorry for wasting your time with the last part, right after posting I found a piece of solder in the trackpad connector shorting it out, once removed all is working fine. Only costed me 2h of my life! Sadly the display is damaged after all, but not related to this repair, client is now deciding if the wants a new display or not. Thank you for the help, this was a really cool repair!

[mon2]

Re: A1706 (820-00923-A) Stuck on 5V/30ma

Very nice. We were on the right track(pad)