820-2936-B No PM_SLP_SUS_L

[max1zzz]

I have a 820-2936-B that's missing PM_SLP_SUS_L (and therefour i'm not getting PP3V3_SUS or PP5V_SUS)
PP3V42_G3H, PPVRTC_G3H, PP5V_S5 and PP3V3_S5 are all present and correct, R7918 measures 99.9K so I can rule that out and am also assuming U7940 is OK as there it no short on PM_SLP_SUS_L

I'm assuming U1800 is dead as I can't see anything else that could be causing me not not get PM_SLP_SUS_L, just wanted to check if there is anything else I should look at before I go ahead and replace U1800

Thanks

 

[2informaticos]

There are more signals required by PCH, before releasing PM_SLP_SUS_L.
Check S5_PWRGD, PCH_DSWVRMEN, PM_DSW_PWRGD, SMC_ADAPTER_EN, PM_BATLOW_L, all 4 RTCs signals (page 16).
Does PCH receive 32KHz from U2800?

 

[max1zzz]

The Voltages are as follows:
S5_PWRGD = 3.453v
PCH_DSWVRMEN = 3.177v
PM_DSW_PWRGD = 3.466v
SMC_ADAPTER_EN = 3.450v
PM_BATLOW_L = 0v
RTC_RESET_L = 3.301v
PCH_SRTCRST_L = 3.300v
PCH_INTRUDER_L = 2.993v
PCH_INTVRMEN_L = 3.193v

I had been assuming PM_BATLOW_L would be low as there was no battery connected, however I have just tested it with a known working charged battery and it is still low. SMC_BATLOW_L is around 3.3v with or so with or without a battery connected however looking at the schematic Q5040 will connect SMC_BATLOW_L to PM_BATLOW_L when PP3V3_SUS is present so as I am missing that I wouldn't expect to have anything on PM_BATLOW_L. I haven't tested SYSCLK_CLK32K_RTC yet as I need to find where my USB oscilloscope has got to

 

[2informaticos]

PM_BATLOW_L has a pull-up resistor inside PCH (20K).
Seems that you have a PCH issue.
Put good flux and heat PCH till 180 degrees; no more than 200.
You only need to burn eventualy crap underneath, not to melt the balls.

"I haven't tested SYSCLK_CLK32K_RTC yet as I need to find where my USB oscilloscope has got to"
You should get aprox 0.45V DC; however that doesn't confirm 100% correct oscillation.

 

[max1zzz]

Ahh ok that makes sense, I'll go ahead and give that a try
I found my oscilloscope and have confirmed SYSCLK_CLK32K_RTC is oscillating at 32khz

 

[max1zzz]

OK, I tried heating the PCH with flux under it, it has made no difference

 

[max1zzz]

OK, I removed the PCH today and found a pretty large number of pads on the right side of the array where missing (Which makes sense as the board was liquid damaged around that area) so this board is now scrap

Thanks for the help!