Need confirmation if PCH is dead

[orientalsniper]

Hello, got a 820-00165, has orange led but won't power on, if I SMC bypass, the fan spins indefinitely, but the PCH/Processor does not even warm up.

Here are the relevant voltages, need confirmation if PCH is dead to inform customer:

PPVRTC_G3H - 0v (4 MOhms)
RTC_RESET_L - 3.3v
PCH_SRTCRST_L - 3.3v
PCH_INTVRMEN_L - 2.4v
PCH_DSWVRMEN - 2.3v
PP3V3_S5 - 3.3v
PM_DSW_PWRGD - 3.4v
PP3V3_SUS - 3.3v
PM_BATLOW_L - 3.3v
PM_RSMRST_L - 3.3v
PM_PWRBTN_L - 3.3v

[reformatt]

More likely you have an issue around U1900, which is quite common given the bottom of the board cops most of the corrosion on this model.

Dead PCH usually presents as a short on PP3V3_S5 or PP1V05_S0. The latter should measure around 150 ohms or more to ground when CPU is cold. Follow the power sequence on logi wiki for this model to troubleshoot.

[orientalsniper]

Thanks reformatt my guy, means there's a chance, will check the wiki later.

[piernov]

PPVRTC_G3H - 0v (4 MOhms)
RTC_RESET_L - 3.3v

Not possible. RTC_RESET_L is pulled up to PPVRTC_G3H.

[orientalsniper]

You are right piernov I must've not touched the probe to ground, PPVRTC_G3H is 3.3v and PP1V05_S0 is around 450 ohms against ground.

I even got the voltages at the end of this power sequence ( https://logi.wiki/index.php/G3_to_S3..._and_Broadwell ). So I guess PCH_INTVRMEN_L and PCH_DSWVRMEN are okay.

[reformatt]

Most common issues on these boards are corrosion on the rear edge facing the keyboard, or minor spots around the board from either liquid or insect damage. Look over the board closely under a microscope for corroded test pads and components. Any components that aren't shiny often have corroded connection to the pad underneath. You need to remove each one, clean up the pads and replace with a component from a donor board. I do this before any serious troubleshooting.

[orientalsniper]

reformatt I've checked and the only corrosion I found was around C3202, R3241 and C3200 relating to Thunderbolt, I really thought I mentioned the history of this device, but apparently I never did, the thunderbolt IC U2800 and the camera IC U3900 were heating up when power was plugged in, so I removed those chips, that was the first thing I did.

At this moment, PM_SLP_S4_L pulses 2 times when power adapted is plugged in.

I checked the the diagram made by piernov https://logi.wiki/images/b/b0/S3_to_S0_State.pdf and I'm not getting PP5V_S4RS3, is this a U7501 fault?

[reformatt]

Double pulse on these boards, I don't have a solution. Have seen this fault many times and fault always comes back to PCH/CPU. I believe a CPU reball would probably resolve it, but I don't have the rework station in which to do it to prove it. I use double pulse boards as donors these days and just replace the board if the customer wants to fix it.

[orientalsniper]

Thanks mate reformatt I'll double check everything again today and maybe do a reflow to PCH, if I don't update this post, that meant I couldn't fix it, thanks once again.