820-00165 (P3V3SUS_EN) RABBIT HOLE TO HELL!! Green light, 0.040 mA current draw.

OK. I have been to hell and back on this board! I know that I am kind of new at this but OMG this board is a bitch!
I did discover some water damage around U7501 but this area has been worked twice now and my 3V3_S5 rail is good.

MagSafe light good
PP3V3 S5 good

P3V3SUS_EN Bad
SYSCLK_CLK25M X1 & X2 missing ( Y1905 crystal is doing noting. Occasional weird pulse no sine wave )
U1900 & Y1905 replaced. (because I am mentally lazy)

U1900 VDD Good 3.3V
U1900 PP3V42_G3H good 3.3V
U1900 P3V3_S5RS3RS0_SYSCLKGEN good 3.3V
U1900 PPVRTC_G3H output good 3.3V
U1900 PP3V3 S5 rail input good 3.3V

U1900 PP3V3 TBTLC missing Voltage is 0.45v I checked for shorts. I am not totally sure what the hell TBTLC means. I seems to be power for U2890 and U2060
U1900 PP1V2_CAM_XTALPCIEVDD missing. I don't care about a camera right?
U1900 PCH_CLK32K_RTCX1 missing. "as to be expected in this state"

I have checked all the local resistors
is it possible that my harvested crystal is also bad? I never see these fail unless dropped.

I just don't have enough experience in this area. Would appreciate guidance.
I have tried to find a data sheet on this chip without success.

I think I am in a rabbit hole and lost!
 
Last edited:

2informaticos

Administrator
Staff member
U1900 area looks good.
25MHz oscillation is NOT in S5 state.

P3V3SUS_EN comes from PM_SLP_SUS_L, do you get it?
You didn't post basic power on signals.
Don't forget to check RTC signals too.
 
I knew I was lost. Thanks!

What turns on Y1905 on U1900?
I totally get I was down a rabbit hole.

I pulled out the Thermal and did find a hot spot.
U1930. It was not making good voltage on the output. There was no sign of water. Checked for shorts found none. Replaced U1930. When chip was pulled there was no sign of water. Hot spot gone. Now the board is pulling 0.15A and still nothing.

but... If I quick bounce the MagSafe it will go into S0 and does power up all the way to a question mark on the screen.

Back to power rail checking.
Now 3V3 S5 at L7560 is 0.5v unless I quick bounce MagSafe. checking that now.

The problem with the 3V3 S5 and having to bounce the MagSafe was PPBUS_G3H not coming up to proper voltage. Each time you quick bounced it would rise a little then slowly fall. Traced that back to U7100 R7121 & R7122.

I now have a working board!!!!!!
Thanks for getting me out of my hole.

I am still am curious about Y1905 powering on. I just cant find a data sheet on U1900.
 
Last edited:

2informaticos

Administrator
Staff member
RTC 32KHz signal is square wave generated by U1900 in base of internal RC oscilator.
25M_A/B/C 25MHz outputs are independently enabled, sine wave oscillation.
25M_A not used, as PCH has its crystal Y1915.
 
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