820-00165 - missing PP1V05_S0

[Atomrepair]

This board has past liquid damage, has been repaired by someone else and now got liquid damaged again, again been to someone else and now ended up with me after they gave up.
About half the IC's on the board have flux there, so either replaced or just reflowed/retouched. To make things worse, a bunch of parts were missing completely from the board. After way too much work fixing this I'm now at the point where most of the rails are present.

Getting into S0, but missing PP1V05_S0. Actually, it was sitting at 0.5V. I got fan spin in this state, but unsurpisingly nothing more.
I replaced U7600 after which PP1V05_S0 is now completely gone. I replaced U7600, thinking I picked a bad one off a donor board, but its still at 0V.

Resist to ground at L7630 is ~180Ohm.
U7600 inputs:

P1V05S0_EN	3,3V
P1V05_S0_VREF	1,8V
P1V05S0_FB	1,05V

I'm not sure what other inputs to check here. Any clues would be helpful!

P1V05S0_DRVH is dead, 0V.

 

[2informaticos]

Check all resistors and traces around U7600 and Q7630.
Pay atention at R7631 and R/C7630.

 

[Atomrepair]

All resistors measured (had to lift some to make sure), all match the schematic in value. I've lifted Q7630 to make sure theres nothing wrong underneath - no corrosion or anything these.
Powered machine on without Q7630 on there, but still got 0V on P1V05S0_DRVH. Caps all looking fine. See attachments for both areas.

 

[2informaticos]

Why the people check the Gate pins for DC voltage, can someone explain me???
There should be PWM signal, but if no output voltage from buck converter, I can 100% assure, no PWM signal present.
And waiting that signal without MOSFET is complete nonsense.

Check continuity between both sides of board in that area.
Board stays on, with missing L7630 voltage?
Check for pulse on it when trigger SMC_ONOFF_L.

 

[Atomrepair]

Why the people check the Gate pins for DC voltage, can someone explain me???
There should be PWM signal, but if no otput voltage from buck converter, I can 100% assure, no PWM signal present.
And waiting that signal without MOSFET is complete nonsense.

I can't speak for others, but; because I often enough don't fully understand the circuitry, but try to find out which inputs or outputs are missing and lead that back to their sources. If I cant figure out what exactly is going on, I have to experiment or post here for advice. I check for voltage on the gate pin because I'm used to voltage showing up there on my MM. Why not?
In this case, the schematic looked to me like U7600 has PP1V05_S0 as both an input and also generates it through Q7630. Confusing.
Now that I looked at it again, I see PP5V_S4RS3 is the main power source for U7600 and pin 2 is at the top (where main VIN normally is shown on a schematic) for some reason.
I don't understand why the chip that generates this rail also has it as an input, considering it looks to be getting feedback from pin 13 and 9 already. So.. chalk that up to not having enough experience/ not knowing enough, whatever.

Anyway, continuity was ok, but now PM_SLP_S5_L and 4 disappeared. I reflowed the SMC and UC'd the board, but no help.

PM_SLP_S5_L missing. no pulse
PM_SLP_S4_L missing. no pulse
PM_SLP_SUS_L missing
SMC_ADAPTER_EN 3.3V
PM_BATLOW_L 3.3V
S5_PWRGD 3.3V

PM_PWRBTN_L 3.4V
PM_PCH_PWROK 0V
PM_SYSRST_L 0V

What is required for PM_SLP_SUS_L to be generated?

 

[2informaticos]

Any reaction at PM_PWRBTN_L when trigger SMC_ONOFF_L?
PCH requires presence of all 4 RTC signals.
Do you get 3V3_S5 at least?
If yes, check also S5_PWRGD, PM_DSW_PWRGD and PCH_DSWVRMEN.

 

[Atomrepair]

When triggering SMC_ONOFF_L, PM_PWRBTN_L is pulled down to ~350mV
3V3_S5 is ok
S5_PWRGD ok
PCH_DSWVRMEN 3.2V
PM_DSW_PWRGD missing

PPVRTC_G3H	3,3V
RTC_RESET_L	3,3V
PCH_SRTCRST_L	3,3V
PCH_CLK32K_RTCX1	0,4V

Last one I assume should be 3.3V. I checked U1900 and the crystal on scope - its not working properly (mostly a flat line, only getting a short wave every so often)

U1900 inputs:

PP3V42_G3H	3,4V
PP3V3_S5	3,3V
PP3V3_S5RS3RS0_SYSCLKGEN	3,3V	straight line on scope
PP3V3_TBTLC	0V
SYSCLK_CLK25M_X2_R
SYSCLK_CLK25M_X1
PPVRTC_G3H	3,3V

 

[2informaticos]

"

PCH_CLK32K_RTCX1

0,4V

Last one I assume should be 3.3V"
Wrong assumption, that is 32KHz square wave; and DC value looks correct.

"S5_PWRGD ok
-------------------------
PM_DSW_PWRGD missing"
Read the note from page 59.
You may need to change SMC; reball it first.

 

[Atomrepair]

Ah, so PM_DSW_PWRGD needs to come out of the SMC if it gets S5_PWRGD as an input. Will report back when SMC is done..

 

[Atomrepair]

Took a while, had to wait for new donor boards. SMC replaced, got quarter fan spin. Turns out I ended up missing PP5V_S0. After fixing that, I found out that CPUVCORE was short to ground inside the CPU. Way too much wasted time, shouldve checked for shorts much earlier Oh well.

 

[2informaticos]

Not wasted time, if this thread will help you solve similar problems in the future...

 

[Atomrepair]

You're right, me and others.. I tend to forget how often I end up fixing things through this forum without having to open a new thread.