820-00239 not turning on

[chedda]

Hi,

I have this board which apparently had liquid damage and been cleaned afterwards.
At least now there is nothing visible anymore.
Voltmeter says 20V at 500-650mA.
ALL_SYS_PWRGD is 3.2V, PPBUS_G3H and _S0 rails present.
Also PPVCC_S0_CPU and PPVCCSA_S0_CPU present.
No USB activity.
CPU gets warm (~50°C without fan), but also U7210 and U7220 are always a bit warmer (~2-3°C).
What can I check next?

 

[2informaticos]

Try known good working BIOS.
Did you test USB activity on all ports?

 

[chedda]

Yes, tried with all 4 ports.

This

How To Read/Write/Erase Apple EFI-SPI-ROM with Raspberry Pi

Here I will explain the way I fixed some boards by rewriting the Apple EFI SPI ROM. You should try this if your machine has the following symptoms: stuck in a start-stop loop without posting it will boot, chime, load the OS, but the WiFi, and/or the graphics will behave irregular. it will...

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method should work right?

 

[2informaticos]

I have never touched a Raspberry device.
Medusa is the best and classic USB programmer is probably more easy to use than Raspberry Pi.

 

[chedda]

I just flashed the SPI ROM. still the same. What can i do next?

 

[2informaticos]

Do you note any variation at PPVCC_S0_CPU in the first 10-15s?

 

[chedda]

No, it stays at 1.05V.

 

[2informaticos]

Then the board doesn't really boot, just stays on.
Where did you get the BIOS file?

Check all SPI Bus Series Termination resistors and their traces (page 59).

 

[chedda]

The bios is from badcaps forum, described as 100% working.
I checked the resistors and traces (except to the cpu pads) and all seems well.

 

[chedda]

Any advice what to do next?
Do U7210/7220 get that hot on a good board?

 

[2informaticos]

Liquid spill near the CPU could be letal...