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Asus B550-E Motherboard repair no power help.

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abel2b:
Hi, I need help repairing Asus ROG Strix B550-E gaming board.

Motherboard died after removing GPU for cleaning, after plugging all back, board is dead no lights on logo, edge leds, DRAM, CPU, Boot LED´s or Q-code display nada!

PSU is ok
CPU tested on another board ok
GPU tested on another board ok
RAM also tested on another board ok.
+5VSB on PSU ok
PSON on PSU ok
+3V on F-panel power button ok
SUPER IO NCT6798D (pin 60 PWRBTN#) high/low ok
PU4000 regulator +3VSB_ATX ok

on PHD6000 header I have

SKTOCC# (3V) ok
3VSB_ATX ok

I do not have 3VSB_SIO on pin 45 of SIO (NCT6798D), RSMRST# or SLP_S3 signal necessary to boot .

I have B550-Plus, B550M-Plus. B550-F boardviews and all have same SIO (NCT6798D) but very different board layout and minor component differences from B550-E...

I have an idea what's going on, but I don´t know what voltages are necessary in standby to make board ready to boot, and which coils on the board are responsible, I´ve checked all coils and didn´t find any shorts but like I said I don´t know which is which or who is supposed to be on while on standby...?

So if someone can tell me what SIO and PCH must have standby voltages to boot or SIO power up sequence it would help a lot, also schematics and boardview would be apreciated...

THX

thm_w:
Cross posted here: https://www.reddit.com/r/AMDHelp/comments/1b6vof9/asus_rog_b550e_dead_no_power/
Please link in the future.

You haven't mentioned it, but I'm sure you've already checked most of these:
- cmos battery is good?
- cmos has been reset?
- BIOS image has been reflashed or verified? (if you have the tools)
- PSU is "ok" but no mention of using another known good PSU to test the system?
- No damage to the PCIE port caused by removing the card?

abel2b:

--- Quote from: thm_w on March 05, 2024, 11:30:16 pm ---
You haven't mentioned it, but I'm sure you've already checked most of these:
- cmos battery is good?
- cmos has been reset?
- BIOS image has been reflashed or verified? (if you have the tools)
- PSU is "ok" but no mention of using another known good PSU to test the system?
- No damage to the PCIE port caused by removing the card?

--- End quote ---

Hi, thank you, for response....
- yes I installed new cmos battery and resest pin ...
- I have tool to flash bios but I didnot yet because RGB Led logo should at least  light up in standby upon powering psu via +5VSB
- I believe PSU is ok, I tested on another system and is working fine
- very close inspection does not shot any damage or bent pin on PCIE slot....

50ShadesOfDirt:
If I were troubleshooting this mobo, I'd have the user guide for it at hand, and I'd strip it down to just mobo, cpu, and ram, and work from there to figure out why it won't even POST. Everything else but p/s disconnected. I'd even put just the essentials on a bench/a-s mat (takes the case & components out of the way), if you have this environment.

If mobo doesn't have built-in graphics, try some other (inexpensive) graphics card for video output, but keep it simple. The expensive graphics card may have some issue of its own (given that you pulled it for cleaning), and you don't want to muddy the picture with it in place.

If still no joy, check mobo for swelling, blown caps and such.

Plenty of internet sites out there for troubleshooting the mobo in a pure "bench-like" test setting, so they guide you further.

Hope this helps ...

Messtechniker:
Sure you have connected the extra 12 V power connector?

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