Dead MSI B450 A-PRO

[pirm]

Hello,

A few days ago, I bought a PC for €45, sold “for parts.”
It came with a Ryzen 5 2600, a Be Quiet! Pure Rock Slim cooler, an MSI B450 A-PRO, 16 GB RAM, a GTX 1060, and an Aerocool KCAS 550G PSU.
The seller didn’t know if it worked because it had been sitting in a basement for about a year. I took the gamble because I enjoy repairing things.

When it arrived, surprisingly the PC booted perfectly (into BIOS, since there was no storage).
Only visible issues: GPU fans were dead and a few USB pins were slightly bent (I fixed those easily).

I updated the BIOS to the latest non-beta version (7B86vAH, 2022).
Update went flawlessly, the system rebooted, and the BIOS correctly showed the new version.

I didn’t have any storage at that moment, so I ordered an NVMe SSD and set the PC aside. One week later, I install the SSD, power it on… and the PC turns on for one millisecond and instantly shuts off.

Of course, I removed the SSD again → still nothing.
I suspected the PSU.
Tried another PSU → nothing.
Another power cable → nothing.
Boot without GPU → nothing.
Boot without RAM → nothing.
Tried another CPU → still nothing.

Basically, the motherboard is completely dead.
With only motherboard + CPU + PSU + cooler + one RAM stick, I get absolutely nothing.
No motherboard fans (CPU_FAN / SYS_FAN), no LEDs, no POST, no reaction to the power button.

Strange behavior depending on the CPU installed:

• With the original Ryzen 5 2600: the board produced a faint, regular buzzing sound in the bottom-left area, near the Nuvoton NCT6797D-M chip.
• With a Ryzen 5 3600: no buzzing at all, but the CPU instantly heats up the moment I turn the PSU ON… even without pressing the power button.

I removed the CMOS battery, tried a new one, reset the BIOS → nothing.

I also tried flashing an older BIOS using the Flash BIOS button on the board → no success.
I only get three quick white flashes and then nothing.
Tried with four different USB sticks, USB 2.0, properly formatted, correct filename (MSI.ROM).

Do you have any idea what could have happened? Is the board completely trash?

I looked for physical damage (capacitors, resistors, VRM) but everything looks normal.
It’s extremely frustrating because the system was working perfectly just a few days earlier.

I know repairing a B450 board isn’t really worth the money (they go for ~€50 here in France), but I’d at least like to understand the root cause.

If anyone has suggestions or tests I should try, I’m open to anything.

Thanks in advance!

[ductranvinh]

Find the 5vsb first and measure this.After then find 3.3vsb, find Rail RSMRST at Q71 and measure it.

Link to schematic & boardview - https://www.badcaps.net/forum/troubl...38#post3170538

[DeXXter]

You have to measure resistance, start for the 12v, 5v, 3.3v, the coils, it looks like you have a short somewhere.

[ductranvinh]

just measure volt first! if 5vsb and 3.3vsb lost, u need to view the boardview to find connect component

[pirm]

Hello,

Thanks a lot for your help. This is my first time measuring motherboard standby voltages, but I think I did it correctly. I measured with a multimeter in DC 20V mode, black probe on USB ground, red on the pin, with 24-pin ATX + 8-pin CPU EPS plugged in, no CPU installed.

Results :

• 5VSB (ATX 24-pin, purple wire, pin 9): 2.46 V
• 3.3VSB (JTPM1 pin 2, top-left): 3.27 V

So I guess the 5VSB is bad. What should I do next ? Thanks a lot.

[ductranvinh]

measure 5VDUAL at pin D of Q61, if u have thermal camera u check some component make a heat.

[DeXXter]

Hello,

Thanks a lot for your help. This is my first time measuring motherboard standby voltages, but I think I did it correctly. I measured with a multimeter in DC 20V mode, black probe on USB ground, red on the pin, with 24-pin ATX + 8-pin CPU EPS plugged in, no CPU installed.

Results :

• 5VSB (ATX 24-pin, purple wire, pin 9): 2.46 V
• 3.3VSB (JTPM1 pin 2, top-left): 3.27 V

So I guess the 5VSB is bad. What should I do next ? Thanks a lot.

Dude you have to measure on resistance, diode mode or biping mode FIRST, voltage comes after that. If you got that voltage on 5v_standby you might have a partial short, measure the resistance on that rail.

[pirm]

Hi all,

Thanks for the tips. I measured resistances :

• 12V rails (pins 10 & 11 ATX 24-pin) → rising until ~4.5 kΩ
• 5VSB (pin 9 ATX 24-pin) → 870 Ω, very brief beep
• 3.3VSB (pin 2 JTPM1) → rising until ~20 kΩ

So I guess it confirms that 5VSB is bad with the 2,46V from before.

measure 5VDUAL at pin D of Q61, if u have thermal camera u check some component make a heat.

• 5VDUAL (pin D of Q61, middle pin) → 184 Ω, very brief beep

I guess it's bad too. This is what it looks like; I don't know if the yellow spot is normal :



Unfortunately, I don't have a thermal camera. I suppose I won't be able to fix it myself because I don't know how to solder, but I'd at least like to know where the problem is to see if someone can fix it.

What should I do next ? Again, thanks a lot for your help. I'm very new to this.

[ductranvinh]

p-p06p03lcga. Normaly it not dead or problem! alway the component short on 5v dual make it hot. Maybe the very bad result is HS_PCH5 is dead because it use 2.5v switching from 5v dual. Good luck....!

[pirm]

Update: I performed further testing and cleaning. I removed the chipset heatsink (FCH1) and found a lot of dust and moisture underneath, which I cleaned with isopropyl alcohol.

I wanted to try again. I connected the 24-pin ATX connector with the CPU installed. The motherboard vibrated, and after a few seconds, I smelled something burning. I turned off the PSU. I touched Q61, and it was literally burning hot, enough to burn my finger :



So, Q61 needs to be replaced, or could the problem be coming from somewhere else?

Thank you for your help.

[DeXXter]

Update: I performed further testing and cleaning. I removed the chipset heatsink (FCH1) and found a lot of dust and moisture underneath, which I cleaned with isopropyl alcohol.

I wanted to try again. I connected the 24-pin ATX connector with the CPU installed. The motherboard vibrated, and after a few seconds, I smelled something burning. I turned off the PSU. I touched Q61, and it was literally burning hot, enough to burn my finger :



So, Q61 needs to be replaced, or could the problem be coming from somewhere else?

Thank you for your help.

Most probably that's the culprit, I can't see what's Q61 on your picture, but now you should check the datasheet to know what that ic does.

[pirm]

Sorry, this is Q61 (burnt as we can see):



I found this in the schematic (red arrow in the top right corner):



I don’t really understand what it means or what this MOSFET is doing exactly.

What should I do? Stop the diagnosis and ask someone to change it? Can you buy this kind of thing?

Thanks again for your help.

[ductranvinh]

https://www.badcaps.net/forum/troubl...38#post3170538
download boardview and you will know how it blow up. Mosfet Q63 give the 5v dual forward to 5v (red line of psu).p-p06p03lcga it not a reason. find R570

[pirm]

https://www.badcaps.net/forum/troubl...38#post3170538
download boardview and you will know how it blow up. Mosfet Q63 give the 5v dual forward to 5v (red line of psu).p-p06p03lcga it not a reason. find R570

R570 : 11–12 kΩ

ChatGPT told me to check U2 (f75504n). Got 184 Ω (one probe on ground, one probe on pin number 1 of U2 (5VDUAL)).

What should I do next ? Q61 burned because it’s in series with U2? So main culprit is U2 now? Thanks.

[ductranvinh]

Sorry now i can’t help because i came home. Tomorrow i will answer u soon

[pirm]

Sorry now i can’t help because i came home. Tomorrow i will answer u soon

Of course, no problem. Thanks a lot for taking the time to help me.

[ductranvinh]

I have 2 solution for u
Solution 1:
First: Replace Q61 it same ic on another board of intel model.
Second: Take down the pin connect with 5v dual of all component
If the load on 5v dual rail stop overload, then reconnet one by one component and look what component short make heat (can touch fast)
Solution 2:
Stream 5v some where out of psu to 5v dual rail, and use thermal camera scan all component connected with 5v dual rail.

[pirm]

Hello everyone,

I finally found the culprit. I only tried the 24-pin connector with a CPU fan (no CPU, no 8-pin CPU).

- With the Aerocool PSU: same symptom as before, the fan lights up for a microsecond and then nothing.
- With a working Be Quiet! PSU: the fan spins, and the CPU LED lights up (which is normal, since there's no CPU installed).

Conclusion: the PSU is dead, and it killed the B450 A-PRO with the Ryzen 5 2600. Since I tried my old Ryzen 5 3600 in it (before knowing PSU was bad), it died too. I tried both CPUs in a working PC, nothing, no boot, no fans.

It's an Aerocool KCAS 550G. I guess it’s dead because of a mix of poor quality and the fact that it had been stored for a long time in a damp basement (it really smells like moisture).

So now when I try these 2 dead CPUs in the B450 A-PRO (with the good Be Quiet! PSU), they heat and it makes a "bzzz" noise. I don't know if the problem is the CPU or the motherboard, but I don't wanna risk another CPU in this B450, even with a good PSU.

I’m sending the B450 A-PRO to a repair technician (Mainboard Medic on YouTube). I will post the video link here as soon as he fixes it.

If you have any additional thoughts or ideas, feel free to share. I’ll keep you updated with whatever the technician finds. Thanks a lot to ductranvinh and DeXXter for their help.

[DynaxSC]

I've repaired lot of PSU's some time ago, and I can only recommend do not buy cheap chinese made noname PSU's like Aerocool etc sold en mass by Amason&Co. PSU is a very critical component in a PC, all these cheap crap is dangerous for the much more expensive components like CPU, GPU and motherboard. All these cheap crap PSU's are badly designed and not thoroughly tested before market release, protections do not work like they should, or they are not implemented at all. Spend some bucks more, be insured and sleep well.

[pirm]

I've repaired lot of PSU's some time ago, and I can only recommend do not buy cheap chinese made noname PSU's like Aerocool etc sold en mass by Amason&Co. PSU is a very critical component in a PC, all these cheap crap is dangerous for the much more expensive components like CPU, GPU and motherboard. All these cheap crap PSU's are badly designed and not thoroughly tested before market release, protections do not work like they should, or they are not implemented at all. Spend some bucks more, be insured and sleep well.

Indeed, I didn't sleep well this night. I tried the "paperclip test" with this PSU and the fan turns on for a split second and nothing. I'm 99% sure this is what killed the motherboard and the CPUs.

I've always read and heard "be careful with the PSU" on the internet. I always thought people were exaggerating a bit, but now, I'll never make that mistake again in my life.

The B450 A-PRO is arriving at the repair shop today; I will post a message when it is repaired to tell you what was wrong with it.