ASUS ROG STRIX B550-F GAMING — Board not powering on properly

[ShadowAi12]

Hi,
I recently bought an ASUS ROG STRIX B550-F GAMING motherboard that was listed as "dead, not powering on." However, it does show some signs of life. I've performed several basic measurements and would like to share the results.

• The board enters a "ready to power on" state after plugging in the PSU.
• Pressing the power button increases power draw.
• Sometimes, touching the RSMRST_L pad with a multimeter probe causes the board to shut off and return to standby.

Measurements:
(taken after pressing the power button, while the board is attempting to start)

• H_SKTOOC# = 0V
• O_RSMRST# = 0V (but 1.8V while in standby)
• O_SLP_S3#_R = 3.3V
• O_IOPWRBTN# = 3.3V
• O_KBRST = 3.3V
• PSON# = 0V
• S_RTCCLK = 3.3V, 500–600 kHz square wave
• LPCCLK1 = 3.3V, no waveform
• LPCCLK0 = 3.3V, no waveform
• LFRAME = 3.3V, no waveform
• PCIE_RST_L = 0V
• VDDQ, VTT, VDDP = not present

• Standby (before pressing power button, including the ATX PSU emulator module): ~120 mA
• After pressing the power button: ~760 mA (including the ATX PSU emulator module)

There is no visible activity on the LPC or SPI buses.
The board does not proceed to full startup.

Do you have any ideas what else I could check, or what might be damaged?

[vilvan4123]

Im also fixing this exact same board, but with no reaction to power button. If I short pin 16 pson to ground the board starts up fine. I think my issue is the SIO as there is no voltage on the PSON rail and therefore it cannot pull the signal low turning the PSU on.

Regarding to your situation, id probably check PCH is getting 1.05V and then check all the CPU VRMS and mosfets make sure everything is there.

I have a boardview for the Wifi variant of the board which I am using on my board to diagnose the issue.

[cobovo]

Use this power seaqvence for gigabyte motherboard. This can help.
And some question:
1 Do you put CPU in socket?You can do it without plug 12V main CPU rail. For check the level of SLP#3 and SLP#4 signals, they must be 3.3V botch, before push POWER BUTTON

[ShadowAi12]

Hi,

My motherboard problem was solved 2–3 days ago after finding that the PL2001 choke was missing. It works as a filtering choke in the network section, so I replaced it using a wire.

I think your problem might be caused by a damaged SIO, because it’s responsible for waking up other lines. Before replacing it, check if you have 3.3 V on PWRBTN#.
If it’s missing, also check if there are any resistors missing on the PWRBTN# line.
Then check the following signals and voltages:

• S_SLP_S3#
• S_SLP_S4#
• O_ATXPG
• +3VSB_SIO
• O_RSMRST#
• X16_RST#

You can also find a good power sequence reference for this board in the ASUS PRIME B450M-K Repair Guide or:
https://www.badcaps.net/forum/troubl...power-sequence

[vilvan4123]

Glad you got yours sorted out.

I am waiting now on the replacement SIO to arrive, will do some more testing as I havent checked S3 and S4. Im assuming those lines should be 3.3v idle. I do think its the SIO as it has all the correct voltages going in, when i press power button it pulls that line low but there is no activity whatsoever on the PSON line. Fortunately I have 2 of these boards at the moment with one that works so I can cross reference.