MacBook Pro A1990 doest turn on

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Confirm that U6940 is being powered. Check the voltage on PP3V3_G3H_RTC_X. - The Voltage is 3.36 v

While there, check the voltage of pins 3 & 4 of U6940. -
the pin voltage is also 3.36V
PMU_ONOFF_L : 3.36v
PMU_RSLOC_RST_L: 3.36v


Check that this value matches BOTH sides of R4911. both sides are 3.36v

The resistance to ground of CHGR_RST_IN_R is too low.

Remove the resistor @ R6940 and then check the resistance again for CHGR_RST_IN_R. Is it still very low ?

If yes, remove the resistor @ R6941 and then check CHGR_RST_IN_R resistance to ground again.

I think that i did a mistake and i measured the resistance when the power was on.
the resistance reading on R6940 and R6941 is 326Kohm

[mon2]

Re: MacBook Pro A1990 doest turn on

What is the voltage of CHGR_RST_IN ?

Measure with the adapter connected.

If 0v then trace it back to the ic referenced in the last post.

[noz_1974]

Re: MacBook Pro A1990 doest turn on

What is the voltage of CHGR_RST_IN ?

Measure with the adapter connected.

If 0v then trace it back to the ic referenced in the last post.

Hey,

The voltage on CHGR_RST_IN is 0V.
which means that if i will remove R6940 and i will get 3.3v on pin10 of U6940 than U7000 is faulty.

If i will still get 0V ( after removing R6940 ) than i need to remove also R6941 which leads to U7800 ( the PMU) and to all the CD3215C . If the voltage will stay 0v than U6940 is faulty , otherwise if the voltage will go up to 3.3v it means that the problem might coming from a short under the CD3215C or from the PMU . And because its a short to ground , so i guess that the problem will come from the CD3215C which was reflow before the falling.
CD3215C pads ( pad 42 CPU_PMU_RESET and pad 51 GND ) this is the short.

Am i right?

[mon2]

Re: MacBook Pro A1990 doest turn on

CHGR_RST_IN is 0V

This means that U7000 is being parked into RESET mode and will not do anything. This signal line needs to be HIGH (~3v3 - assuming) to allow for U7000 to communicate back to the I2C (SMBUS) master to perhaps kick in the higher PPBUS_G3H voltage value.

If I understand correctly, the fault is @ U6940. I would consider to apply flux and hot air to 'make it dance' and then check again. Believe that the CHGR_RST_IN line should be HIGH if the inputs are HIGH.

If you remove R6940, then believe that the CHGR_RST_IN line will be just floating - unless there is an internal pull-up inside of U7000 which is an unknown.

You can remove R6940 and check the voltage on R6940, pad # 2. What is the voltage value ?

If the voltage of the CHGR_RST_IN does not return to a logic HIGH then U6940 needs to be replaced. We could 'hack in a mod' but best to use the Silego part that is in the design for a simple fix.

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Hey mon2,

Yes you right, and i think that we actually meant to the same thing.
but you already few steps ahead.
I forgot that i measured the resistance on CHGR_RST_IN_R and CHGR_RST_IN , and i got high resistance around 326kohm. It means that i dont have a short path to CHGR_RST_IN from the U7000 and i also dont have a short path to CHGR_RST_IN_R ( UPC_PMU_RESET) from the PMU (7800) and from the CD3215C chips. Are you agree ?

This only leave us with a problem on U6940 , and to check this scenario as you mentioned.
I will remove R6940 and will let you now , if you have a similar board on your table can you please confirm and post the voltage on CHGR_RST_IN.
thanks

[noz_1974]

Re: MacBook Pro A1990 doest turn on

Hey ,

I meant short path to ground on my upper post