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Did my mobo die while sitting unplugged? (was "Please help me check my power supply")


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Cliff Notes version of my issue.  Started a new build last year.  No issues, but wasn't decided on which OS to install so I set it aside (unplugged) and went on with my life.  Plugged it in recently and it won't POST, just power cycles.  Everything lights up, the CPU fan spins, but nothing on the screen at all.  It's *not* the monitor (I'm not that stupid).  No speaker so no beeps to tell you about.

The video card and SSD both work when I moved them to another build.  Don't have a compatible system to test the RAM or CPU in.  Cleared the CMOS and also tried a new battery.  I thought it must be the mobo, but in Googling about the issue I read that the power supply could partially power up the system but not be putting out the full 12v at the rails.

I have a multi-meter but haven't touched it in years.  Please tell me how to set the dial and what to touch the probes to so I can diagnose this further.  The PS is an EVGA SuperNOVA 650.  https://preview.tinyurl.com/y9gb2we4

Thanks.

Edited by E-66
clarification
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Set the multimeter to V DC (the "=" symbol), likely you have a range selection *like* 2-20 V, or anyway select the lower V = selection that is at the higher end bigger than 12 V,  then use the probes on Yellow and Black wires.

Cables on ATX power supplies are colour coded, they are all the same, anyway this is the specific supernova detail:

https://pc-mods.com/blogs/psu-pinout-repository/evga-psu-supernova-cables-pinout

You will need a short piece of wire or a paper clip between the Green and *any* black to power on the PSU.

Seemingly however some newish PSU's (including EVGA ones) use NOT colour coded cable so you will need to go by place/number on the connector, see:

 

 

BUT, you won't get a definitive result :w00t:, as very often a faulty PSU still provides the voltage without load, but it doesn't provide enough current, so testing only the voltage is only part of the issue.

You would be better served by a specific/dedicated ATX PSU tester (you can find one of them for anything between 5 and 30 bucks, but that would be (IMHO) wasted money, unless you happen to do many repair/checks.

I.e. if I were you I would get an el-cheapo (but not el-cheapest, no-name), ATX PSU 500-600 W to keep as spare and for testing, you will be spending anything between 10 and 30 dollars, i.e. roughly the same as the tester.

jaclaz

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Post the model of the motherboard.

If it is a modern board, make sure you are using all of the power connectors as outlined in the manual. For example, it is possible to get this behaviour if you do not connect the 4-8 pin CPU power connector. Some modern boards have multiple.

You can also test trying to power on the system without any hardware besides the CPU installed. The test here is to see if you can get an error due to the RAM missing. A lot of boards will beep in this instance. Also I would reseat the CPU and inspect the socket to make sure there aren't any bent pins.

The power supply tester I have is useful only to see if all the appropriate lights turn on (knowing that some PSU have no -12v) and if the wrong lights appear then the PSU gets RMA or thrown into the trash. I've never had to go to the length to attempt to fix a PSU that doesn't work on the tester.

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Sorry, I posted right before I went to bed.  Thought I included all the info, but obviously not.

Mobo - ASRock AB350M (horrible reviews now, but not when I bought it): https://preview.tinyurl.com/ybcnxwbv

First gen Ryzen CPU: https://preview.tinyurl.com/yacapzmn

RAM: https://preview.tinyurl.com/ybd9ya93

This PC worked flawlessly for the short time I used it.  All I did was unplug it from the wall and set the project aside for a while.  Is there really any reason I need to re-seat the CPU?  The EVGA PSU came with one of those dummy plugs to snap on the end of the power cable for the mobo.  The fan spins.  However, I had read that that wasn't a good enough indicator that the PSU was functioning properly, so that's why I thought I needed to do further testing with a multi-meter.

Another bit of info I forgot to mention was that I took the PSU from my current working system and hooked it up to the non-working one.  When I press the power button things light up only briefly.  The fan on the CPU spins a few times and then stops and all the lights go out, and it doesn't power cycle.  The PSU is a Corsair CX500M: https://preview.tinyurl.com/y8z246sm

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Ah no, with a Ryzen it is different. The socket doesn't have the delicate pins on this model.

This board only needs the 24 pin ATX and the 8 pin EPS connector. Try with those and remove the other modular cables. See if you can get the system to turn on with just the CPU installed and no ram or the video card inserted.

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I tried what you said.  It turns on and looks fine (case fan & CPU fan spin), but it just power cycles every 25-30 sec.  What's next?

What is the reason it would barely power on at all when I connected the PSU from my working system to it as I mentioned above?  That PSU has the same 24 & 8 pin connectors, but it'll barely turn on and then shut off and not come back on.

Edited by E-66
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Put in the memory, then video card, then walk back from there.

Also in your previous post you said you took a PSU from a working system and tried on this, did you also take this PSU and try in that system?

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Apologies, I didn't get a notification that there had been a reply.

Yes, the PSU from the system that won't boot works fine in the system that does.  Using it right now, in fact.  That rules out the PSU, but does that also automatically indicate that the culprit is the mobo in the system that won't boot?  I've tried everything you said above, and I believe I did those things before I even posted.  Nothing ever shows up on the screen, and it always power cycles at the same 25-30 interval.

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So it doesn't POST (or attempt to) with only CPU installed, then you are likely down to just the CPU or Board. However, there is one possibility remaining and it is a long shot. Improper mounting/grounding can cause this type of issue. I have seen it a few times over the years, such as a board not booting in one particular chassis, but worked on box or in another. This happened to Shiva where that Intel board would boot on box, but not in an Intec chassis, but then would boot in another one I had laying around.

By "on box" I mean to put the board on top of a box, I usually use the motherboard's box.

Otherwise, the other next step would be to get another CPU to try.

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I found an old case speaker and hooked it up to my working system and heard the familiar single beep when it booted.

Went to the problem system and took the board out of the case as you suggested, connected the speaker, turned it on with just the CPU, and not a single beep, just the power cycling as already described.  It's like the board passes electricity but nothing else.

At this point I guess I either take it somewhere local and have them test the CPU and/or board, or just order a new board, unless there are any other suggestions?

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  • E-66 changed the title to Did my mobo die while sitting unplugged? (was "Please help me check my power supply")

I had something similar during the infamous capacitor plague era (2004 smth). So it's quite possible the capacitors on your mobo went bad. Also , you may try to disassemble everything , remove the CMOS battery, short it's pins and let it rest for a while , two weeks maybe. 

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Clean of any foreign objects, including inside all slots and sockets. Moths like crevasses.

Plug in cooling fans.

 

Edited by jumper
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Only work on the machine with PSU mains plug unplugged. You need RAM installed for boot to get the video output. Use only one RAM stick and video card. You will know from before approximately how long it took to boot, only allow that time and a bit more do not wait 25 seconds your CPU is probably getting hot. Plug in PSU to the mains once you have the video card and Ram stick installed. Be careful with the RAM stick and make sure it is seated properly. Turn on the start button on the case wait 5 seconds if no boot pull the PSU mains plug out wait about 5 seconds and plug the mains plug back in then press the case start switch again. The idea is that there will be still some residual voltage on the busses before you cycle it again. Try a different RAM stick with the procedure and try a different video card. If you have both nVidia and AMD cards then try both. If you are using an air cooled CPU it may not be enough, there usually is not enough heat conductivity from the CPUs copper plate though to the cooling grid and if so then water cooling is most likely essential. If you have it booting again manually setting RAM speed back from auto if allowable might help with this start problem.

Edited by Goodmaneuver
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*****
E-66 wrote:
At this point I guess I either take it somewhere local and have them test the CPU and/or board, or just order a new board, unless there are any other suggestions?
*****

It's not clear you tried someone's earlier suggestion - remount the CPU? Simple task provided you have thermal paste. Query whether the system is cycling due to an instant overheat. There is possibility motherboard capacitor(s) died in storage. Personally i think it's better to use hardware regularly to keep it powered up and active.

One possibility may have been loose connective debris on the motherboard or lodged between the motherboard and case but presumably you would have noticed this when you tested the motherboard on a box.

Have you ruled out a faulty power or reset switch on the case? If not already trialed disconnect the power and reset switch leads from the motherboard. Identify the two motherboard pins for the power switch and short them together with a flathead screwdriver (conductive tip, insulated handle) to start the computer. Off chance that a switch is flaky.

Personally i don't think it's worth taking old hardware to someone who intends to get paid to take a look. If it comes to this the money is better spent buying additional hardware, at least you'll have something to show for the money. Good luck.

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