MacBook A1466 820-3437-B No power

[AlexVG]

Hi.
I have MacBook A1466 820-3437-B
PDDR_S3_REG is 1.2V
PP3V3_S5_REG is 3,3V
PPDCIN_G3H_ISOL is 16V
PPBUS_G3H is 8,6V
Looks like everything ok,


BUT
On PP5V_SRS3 instead of 5V I have only 3.1!
L7630 only 0.06V

Other interesting things are:
- On L7320 (PPVCC_S0_CPU) is 280 Om instead of 18 Om
- I dont see the exchange on SPI at all. There is only the first drop to zero, but there is no answer.
Who should ask SPI?

SMC or Processor?



So, I have already replaced

SPI, SMC, U7501, Q7520
U8130 I restored after liquid damaged.
But have nothing changes!
Would you help me please. I have not any ideas.
Thank you.

[mon2]

Re: MacBook A1466 820-3437-B No power

Remove all power. Meter in resistance mode.

For any rail that is low in voltage, check the resistance to ground first.

Post the measurements.

[AlexVG]

Re: MacBook A1466 820-3437-B No power

Hi,
Of course, I have them.
PP3V42 jumps from 35 kOm till 50 mOm
Thank you

[mon2]

Re: MacBook A1466 820-3437-B No power

That rail is ok on the resistance. Do you read 3v42 on that rail ? If yes, it is fine. If you see a green / orange light on your magsafe head, this rail is working.

Measure the resistance to ground of PP5V_SRS3 since the voltage is low. With no power of course.

[AlexVG]

Re: MacBook A1466 820-3437-B No power

Yes, I can see green/orange light.

I cant find PP5V_SRS3
If you mean PP5V_S5 (L4820) it is 0.5 mOm

[mon2]

Re: MacBook A1466 820-3437-B No power

On PP5V_SRS3 instead of 5V I have only 3.1!
L7630 only 0.06V

From your first post...the above are at a lower voltage? If yes, check their resistance to ground but with no power to the logic board. Check each.

[AlexVG]

Re: MacBook A1466 820-3437-B No power

It is L7630
It has 220 Om,
Its OK

[AlexVG]

Re: MacBook A1466 820-3437-B No power

Who asks SPI first?
CPU or SMC
I guess problem is here, because SPI does not answer. There is no exchanging.

[mon2]

Re: MacBook A1466 820-3437-B No power

SMC is ok since ppbus_g3h is 8v6.

What is the voltage to ground of ALL_SYS_PWRGD?

Review the mix of articles here:

https://www.it-tech.com.au/mac-q-a/m...npocDVXMXdZbC0.

https://www.it-tech.com.au/mac-q-a/pm-slp-s4-l-timing/

https://www.it-tech.com.au/mac-q-a/macbook-smc-circuit/

[AlexVG]

Re: MacBook A1466 820-3437-B No power

Hi.
It is very useful information.
Thank you.
In my case ALL_SYS_PWRGD is down of course, because missing 5V and 1.05V
I checked all rails.
I am sure I have 5V problem, but i dont understand why.
Instead of 5V I have 3.31V
The resistive divider (R7520/R7521) was damaged by fluid, but I restored it.
The calculation shows that it works correctly (in case 5V on out).
But if I set 3.19V to out from resistive divider I get 623 mV instead of 1.012 that I have really (on calculation)
if I look at gates responsible for 5 volts with the osciloscope, I can note rare pulsation.
I have not idea why U7501 works not correctly.

[mon2]

Re: MacBook A1466 820-3437-B No power

Remove all power.

Measure the resistance to ground of PP5V_S4RS3 rail @ L7520, pin # 1.

There may be a low resistance (high load) on this rail causing the voltage to be a lower output.

What is the resistance value ?

[AlexVG]

Re: MacBook A1466 820-3437-B No power

Hi,
Problem was in R7521 resistor!
I have replaced R7520 and R7523 before.
R7521 looked perfectly, and showed 10 kOm and I have left it.
However according my calculation the divider did not work right.
I removed R7521 and found out that it is floating.
I replaced it with a new one.
All runs!
Thank you for your help. These posts answered for all my questions.

[mon2]

Re: MacBook A1466 820-3437-B No power

Very nice! Thanks for the updates and closure.