MacBook Pro A1990 doest turn on

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Hey Mon2,
Thanks

I as wrote 1.1v is missing for U3200 chip and I think that its the master USB C chip.
I checked the resistance on C3204 and I got 25.28K.
I didn't remove the board yet and waiting for the pars to arrive. I need to replace U7650 before testing the USB C chips again.
But from all the data that I gave , do you think that the problem is in U3200 ? and this is the chip that I need to replace ?
Moreover , as I said I have an access to BGA soldering automatic machine , so I hope not to have so many problems in replace it.
Do I need to look on other stuff ? maybe the ROM chip need to be replaced ? maybe its only a T2 chip problem and I need to restore it?

Nitzan

[mon2]

Re: MacBook Pro A1990 doest turn on

The missing 1v1 on U3200 is key. Gathering as this rail is not working, the component could be defective. The power delivery spec is a mess. For our company when I was working with PD 1.0 spec products, I almost burnt my hands in testing a very expensive USB PD ACTIVE cable with the VIA Semiconductor chip (to deliver 20V @ 5A). Reported the findings to Taipei and they claim they fixed the fault. Many years later, similar power delivery controllers offer 'hot swap' protection when the USB connectors (male & female) slide off at an angle.

Otherwise, the CC1 / CC2 lines get hit by 20V and often kill the IC - as per your case.

Personally have not worked with the T2 rom, etc. I think @Stephen and a few others here have experience in this field.

From assorted posts, the operation of USB C controllers is vital but so is the firmware for the T2 chip.

On this note, have you taken resistance checks (no power) for each coil on the board ? The reason is to confirm that there is no damage to the T2 or CPU components. A very low resistance is often game over for both such devices.

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Hey Mon2,

I didn't check the coils.
which coils to check ?
And I will Try to correspond with @Stephen to hear his opinion.
From Louis Rossmann's video, there are some cases where the USB C in all four ports is stuck on 5V and drawing 300mA and the problem was the T2 firmware.
I need to understand how can I roll out T2 firmware problem before de-soldering U3200 (CD3215C).

please point me out to the coils.
thanks,

Nitzan

[mon2]

Re: MacBook Pro A1990 doest turn on

Remove all power. Meter in resistance mode (2k is ok).

Red meter probe to a coil (either side) - they will be grey in color.

Black meter probe to ground. Searching for coils with a very low resistance to ground.

So for example, 2 ohms, etc. will be one to investigate. Check each and every grey coil on the board with the same method.

[mon2]

Re: MacBook Pro A1990 doest turn on

See attached.

Confirm the voltages on the pull-up resistors for EACH I2C bus master.

That is, the logic board has:

1 * I2C Bus Master and controls 2 * ACE controllers over this bus

then

another I2C Bus Master does the same with the other side of the logic board.

We need to be 100% sure the voltage is ~3v3 for each.

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Hello Mon2,

I just check the resistance of the coil to ground:

Coils around CPU heatsink :
LA640- 2.4 ohm
LA650- 2.4 ohm
LA340- 2.7 ohm
LA-300 - 343 ohm
LA350- 24.6 ohm
L7231- 3.7 ohm
L7330- 19 ohm
L7221- 3.4 ohm
L7211-3.3 ohm
L7420- 6.1 ohm
L7410- 6.1 ohm

Some other Coils with ohm resistance to the ground:

L8102 - 66 ohm
L7701- 177ohm
LB700- 588ohm
L9020 - 648ohm
L9021 - 648ohm

all the other coils' resistance to the ground is above the kohm , I have all the data if it can help.

Thanks
Nitzan

[mon2]

Re: MacBook Pro A1990 doest turn on

A few of the coils look low but upon a closer inspection, these are sub-one volt rails so they are fine.

Proceed to replace the ACE controller.

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Thanks,

I will replace first the QFN chip U7650 ( PMIC), and afterwords will replace the ACE.
will keep you update.
thank you very much .

[Ksansan]

Re: MacBook Pro A1990 doest turn on

Greetings, I'm new here, sorry if anything is wrong.
I have the same problem, the A1990 stopped turning on.
The 3 capacitor in the red circle have a resistance of 1.0 ohm, is this normal?
I don't have a wiring diagram yet, so please help with advice.

[mon2]

Re: MacBook Pro A1990 doest turn on

Hi. Welcome to the forum.

1) The schematic & boardview files for your logic board are posted here:

https://www.badcaps.net/forum/showth...ht=820-01814-a

2)

The 3 capacitor in the red circle have a resistance of 1.0 ohm, is this normal?

No, not normal. This is a very important power rail, PPBUS_G3H.

See attached. PPBUS_G3H runs all over the board.

Are you sure the 1 ohm resistance is down to these 3 caps ?

That is, the low resistance may be on another cap somewhere else on the board but still on PPBUS_G3H rail.

To view the locations, review the boardview file and select the '+' terminal of any of these 3 tantalum caps, then the dark yellow dot will light up all points of connection. Zoom out and pan across the parts on the drawing to view where the PPBUS_G3H rail travels.

Search for 'PPBUS_G3H' on the schematic to review the same details.

Check the resistance to ground on fuse F7000 / F7001 - check BOTH sides of the fuses.

3) Are fuses F7000 / F7001 blown ? If not blown, consider to hot air remove the fuse (for now and testing). Once off the board, check the resistance to ground on both pads for F7000 / F7001 fuses.

Is the 1 ohm resistance to ground on the source side (ie. U7000) or the consumer side (downstream) ?

4) Do you have a regulated but adjustable power supply ? Not yet, but this may be leading to voltage injection BUT it must be done with care (0v8 is my personal choice) + alcohol on caps like you have noted. The shorted part will then heat up and mist up the alcohol. But not yet till more is known as this procedure can also nuke the CPU, etc. which are low voltage rails on the logic board.

[Ksansan]

Re: MacBook Pro A1990 doest turn on

Thank you for your help! Went over the board, all capacitors on this bus have a short.
Soldered off 2 fuses, short to the common wire circled in red. Went looking for a regulated current source.

[Ksansan]

Re: MacBook Pro A1990 doest turn on

I found a voltage source of 1.2 volts. Is that a lot? I can limit the current to any value.

[mon2]

Re: MacBook Pro A1990 doest turn on

So the shorted cap is in on the downstream (consumer) side.

What is the history of this failure ? Did it just stop working one day or any known liquid damage ?

Recommend to use the meter in resistance mode (2k scale is ok) and check the resistance to ground on every coil on the board. This is just to be safe to locate any other possible failed buck regulator. Post the location of any low resistance to ground coils.

In panning across the schematic with this rail, most likely it is a bad bulk cap. The cluster from your first post is a good candidate for the root cause since this rail is to supply heavy currents.

Once you find a stable power supply - there are relatively low cost tools on Aliexpress for 'short killer' functions.

Here is a good video on the use of a power supply to locate the fault:

https://www.youtube.com/watch?v=EWuzmIz7hOE

He is very good on his videos.

Here is another on topic:

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

If you proceed, keep the voltage down as noted before, personally like 0v8. Mist the board with suspected regions with alcohol. The 3 caps you first posted are an excellent start. Then look for the mist or evaporation of the alcohol. Once found, remove that component and test again for the resistance to ground.

PS: Great choice of the multimeter. Picked one up in new one in the past few weeks from a local private sale. Love this meter and is built like a tank!!

[Ksansan]

Re: MacBook Pro A1990 doest turn on

The computer was working fine, was turned off by closing the lid.
And a few days later, it just wouldn't turn on.
I haven't found any traces of moisture anywhere yet.

I found a 0.8V 3A power supply.
Thanks for the video, I will study it, and then I will torture my board
��

[Ksansan]

Re: MacBook Pro A1990 doest turn on

Is the resistance suspiciously low?

All other coils on the board have resistances well over 100 ohms, I think they are serviceable.

I connect 0.8 volt to the top pad of the fuses (where the short circuit is).
Minus to the common bus.
When the voltage is applied, I see 4 amps of current, wait 3-4 minutes, no element is obviously heated.

There is 12.27 volts on pin 1 of the fuse.

[Ksansan]

Re: MacBook Pro A1990 doest turn on

Some advice.
When I connect a 0.8 volt current source, the voltage drops to 0.005 volt with a current of 4.1 amps.
Apparently I have a complete short circuit.
All capacitors have the same 0.005volt.
I think the capacitor will not give that much of a short.

I connect the plus to the fuse, the minus to the common wire.

Apparently because the short circuit is so strong, nothing gets hot.
Which way should I go next?
Increase the current to 10 amps?
Won't the copper tracks burn out?

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Hey ,

In my opinion, don't increase the current.
The voltage is dropping because of the short circuit.
Did you check heating on all the components to which PPBUS_G3H is connected, of course with alcohol evaporation? If you have access to a thermal camera it's also a good option.
But, because I am also new here I will let @Mon2 share his thought, he has a lot of experience

[Ksansan]

Re: MacBook Pro A1990 doest turn on

Hi!
F7000-F7001 fuses have 24 amps, so I think the current can be increased.
But of course I would like to hear the opinion mon2

[mon2]

Re: MacBook Pro A1990 doest turn on

Hi. Something should be heating up but perhaps not obvious at this time.

1) Remove all power.

Meter in resistance mode.

See attached. Post the resistance to ground for each test point.

1&3 are the same so one test will do.

2) PPBUS_G3H converts to PPBUS_HS_CPU - see sheet 67 of the schematic on how this same voltage rail is used as a 3 phase power supply. This rail is intended to switch upto 128A of current. There are many linked bulk caps for this low voltage rail.

Are any of these heating up during the power supply injection tests ? Mist the cap cluster with alcohol and then apply the 0v8 from your power supply.

Technically, from the schematic, the voltage rail is adjustable and can support higher potential so it should be ok to dial up the power supply to 0v9 (for now, not higher) and test again. Suggest to dial up the power supply FIRST and then mate the connection to the logic board. We do not want to overshoot the PPBUS_G3H rail incase it is shorted to the CPU rail.

Based on the details of this logic board, the CPU should be ok but most likely a bad cap is still causing this event. As you increase the power supply, some defective component will rear its head.

[Ksansan]

Re: MacBook Pro A1990 doest turn on

Good afternoon! The results are as follows:

UPD: The same results for QB701