00165 missing PM_SLP after ultrasonic

[daniel_andrei1996]

Alright, this one kept me up all night.
Have an 820-00165 that came in with corrosion in a few places, namely around U7600 and R1673 area. Was missing S0_CPU originally, replaced a resistor for S0 cpu power (can't remember which one, sorry) and that fixed it, managed to boot into os and everything. Also replaced a few other corroded components, tested again, still working fine. Put board in ultrasonic to clean, a few hours later after drying board won't start, I get green light and S5 rails, but no S4. Also missing PM_SLP_S5/S4.
I have 32khz clock and pp3v3_sus, but it doesn't seem like PM_SLP_S5 or S4 pulse when triggering SMC_ONOFF.
I'd really appreciate some advice, feel like I got stuck. Thanks

 

[2informaticos]

Possibly knocked off component; especially if you didn't use sweep function on UC.
Broken trace is also possible.

Check the signals involved in power on sequence.

 

[daniel_andrei1996]

Hi! I did use sweep function, but still, sometimes things happen I guess.I've had another look at the board and I can't really see anything ripped off.
I'm sorry, I'm not intimately familiar with the power on sequence on these. Where can I find it/what signals should I be checking?

 

[2informaticos]

Check PM_BATLOW_L, PM_RSMRST_L and RTC signals.
Trigger SMC_ONOFF_L and check for drop pulse at PM_PWRBTN_L.
If yes, check for pulse at PM_SLP_S4_L at same time.

 

[daniel_andrei1996]

PM_BATLOW_L	3.316V
PM_RSMRST_L	3.287V
RTC_RESET_L	3.313V
PCH_SRTCRST_L	3.313V
PCH_INTRUDER_L	3.023V
PCH_INTVRMEN	3.214V	PCH_INTVRMEN_L not found
PM_PWRBTN_L PULSE	3.412V NORMALLY, DROPS TO 0.345V WITH ONOFF
PM_SLP_S4_L PULSE	NO PULSE, 0.02V

 

[2informaticos]

"PCH_INTVRMEN_L not found"
Does not even exist...

I suppose PM_DSW_PWRGD is OK, if you really have 3V3_SUS; and implicitly PM_SLP_SUS_L, of course.
PCH_DSWVRMEN also present?

Trigger SMC_ONOFF_L repeatedly and monitor all PM_SLP_Sx_L signals.
Is better to use an o-scope, it can catch any fast pulse.

If still no pulse, heat PCH with quality flux...

 

[daniel_andrei1996]

yes sorry, think PCH_INTVRMEN_L is on other boards.
I'll check all signals and report back. if I heat PCH, should I clear edge bonding on cpu first, or just flux and boil at 150-200C as it is?
Thanks

 

[2informaticos]

You can remove edge resin on PCH side; not really needed, but not too complicated.

Don't search for PCH_INTVRMEN_L on any board; good enough if you find PCH_INTVRMEN...

 

[daniel_andrei1996]

so, I kinda got busy with other jobs and put this aside for a week. Yes I have PM_DSW_PWRGD at 3.4v and PCH_DSWVRMEN at 3.2v.
Still can't see any pulses on pm_slp_s5, s4, s3. I have one of the small "pocket oscilloscopes". I know they're generally junk but I've used it before to see pm_slp pulsing, so I should be able to see the pulses here too.

I removed the CPU edge resin and heated with amtech 559 at 200C for about 1-2 minutes. Sadly no result from this. Maybe my amtech is fake (from ebay) but it's worked well for normal soldering and cleaning corrosion.

Anything else I can try? It kills me that the board was working before going into the cleaner, never had it kill a board before

 

[2informaticos]

Possibly brokem trace, or knocked off component in cleaning process.
I don't see other option, if board worked before UC...

 

[daniel_andrei1996]

I see, I guess it goes back to bottom of the pile. I'll keep looking, hopefully I find something. Any area I should check in particular?

 

[2informaticos]

Reball SMC, just in case...

 

[daniel_andrei1996]

reballed smc, then replaced with other 00165 smc, still no change