Why won't my new homebuilt PC start?

January 14, 2023 5:06 PM

I built a computer, it won't start/POST and I think I've tested everything. Is there something obvious (or subtle) I'm missing? (This is my second homebuilt PC; my first was 10 years ago so I'm not a seasoned builder.)

Ryzen 5600G, Asus TUF B550, Kingston Fury 16GB DDR4-3600. PCpartpicker says everything is compatible.

I have tested the motherboard with CPU, memory, SSD and nothing else and when I turned it on:

• the decorative LEDs on the motherboard and RAM light up and the fans start
• there is no POST beep (a speaker is connected)
• the DRAM error QLED lights up
• there is no video signal output although a connected monitor wakes up

I have re-seated the RAM multiple times, checked the connectors, moved the RAM to a different slot, reseated the CPU and checked cables and screws.

I swapped the new RAM with known good RAM from my workhorse PC and the new computer's RAM worked in the workhorse PC whereas the new PC gave the same DRAM error with the working RAM.

I assumed it was therefore not the RAM but likely a motherboard or CPU error and took the motherboard with CPU, memory and SSD into my trusted local computer shop to check and figure out which.

A friend collected the motherboard from the shop yesterday and relayed the message "we updated the BIOS because it didn't work with the GPU we put in, we moved the RAM to a different slot and it's working fine". This confused me a little, since the original slot was definitely the one suggested in the manual and I hadn't tested with a GPU.

I tested again today and it gives the exact same error as before. I tried a different PSU from a working PC which didn't help. I can't understand why it worked for the repair shop but not for me. Often when I am baffled by computers it's because I'm missing something screamingly obvious. Before I take it back to the shop on Monday is there anything I might be overlooking?

posted by Busy Old Fool to Computers & Internet (14 answers total)

Any chance there's something lodged in the RAM slot that's preventing a good connection? A little bit of dust or something?
posted by Blue Jello Elf at 5:15 PM on January 14, 2023

I had a similar problem once, though I solved it fairly quickly. The particular motherboard I was using required more than the usual amount of force to seat the RAM completely. If you pressed down with a moderate amount of force, the RAM partially seated, but you needed to keep pushing for it to go all the way into the slot.
posted by alex1965 at 5:53 PM on January 14, 2023 [1 favorite]

Best answer: When this happened to me, it was because I overlooked a second 4-pin power connector to the motherboard next to the CPU.
posted by Maxwell_Smart at 6:03 PM on January 14, 2023 [9 favorites]

Best answer: Every time I've had similar problems (a while ago now, tbh, as I've moved Mac-side but still I built 5 machines back in the day and OC'ed two of them) it was because I hadn't seated something correctly, because I was hyper-paranoid about cracking solder somewhere.

...but in your specific case I concur that perhaps your PSU is not sufficient, or you've missed that second connector (if it uses one).
posted by aramaic at 6:07 PM on January 14, 2023

Also, quick googling suggests that there could be multiple additional power connectors near the cpu, and that you should carefully follow motherboard instructions to see which ones are preferred, or whether you can use all of them at once, or only one or the other.
posted by Maxwell_Smart at 6:07 PM on January 14, 2023

Best answer: If the computer shop was able to get the motherboard to post with your CPU and RAM it sounds like a power issue. Check your CPU and motherboard power connections—did you connect all required power? If so, are they all seated correctly?

Since your case fans and motherboard lights work, you can rule out a PSU issue, most likely, which is probably why testing with another PSU didn’t solve the problem.

By the way, if either of your PSUs are modular, NEVER mix the power cables. Just… don’t.
posted by rhymedirective at 6:48 PM on January 14, 2023

Oh, and disconnect the SSD while you work this out. It’s rare, but I have seen issues with post caused by boot media.
posted by rhymedirective at 6:53 PM on January 14, 2023 [1 favorite]

I honestly haven't processed all of the symptoms and suggestions above, but for these kinds of problems the first step is always to suspect the power supply. In that same vein I also like Maxwell Smart's answer(s).
posted by intermod at 9:09 PM on January 14, 2023

I put more RAM in my homebuilt setup last week. It wouldn't boot. My kid said, "Why don't you turn the monitor on?"
I didn't turn it off. It had a light on. Still, he pressed the power button and it worked.
Generally, for new builds, I use an old glass monitor and run it to the onboard video. If that works I put the proper video card in. Also you can download a bootable linux and boot off that, just to see if anything's bad.
A lot of modern systems don't make POST beeps.
If you have more than one stick of RAM, only use one at a time, and try different ones.
posted by AugustusCrunch at 10:54 PM on January 14, 2023

Response by poster: I'm grateful for all the answers and I appreciate there were a lot of details in the question to read through. So I'm going to repeat the parts of my question that were most often overlooked to try to head off further suggestions I've already tried.

Something lodged in the RAM slot / RAM not seated correctly

• I have re-seated the RAM multiple times
• I've moved the RAM to different slots
• The RAM worked in the current slot in the computer shop but did not when I got it home

Try different sticks of RAM

• I swapped the new RAM with known good RAM from my workhorse PC and the new computer's RAM worked in the workhorse PC whereas the new PC gave the same DRAM error with the working RAM.

PSU not sufficient / faulty

• I tried a different PSU from a working PC and it didn't change anything
• The fans and case lights come on when the PSU is connected
• The PSU is 650W (OK, this info was not in my original question!)

Try the onboard video first and then add the video card

• I have only tested with onboard video and haven't tested it with a video card

posted by Busy Old Fool at 2:31 AM on January 15, 2023

Response by poster: The answers about the additional power connector are intriguing; I don't remember connecting anything except the 24 pin supply so I'm going to look into that.
posted by Busy Old Fool at 2:51 AM on January 15, 2023

Best answer: Yeah it looks like this board has an additional 8 pin power connector for the cpu, which the manual says is required separately from the 24 pin power connector (it’s marked EATX12V on the diagram and this is the manual I referred to just in case I’m looking at the wrong one)

Btw it’s a good idea to run memtest on new RAM even if it works on another PC, although in this case it’s unlikely to be the problem
posted by TwoWordReview at 3:44 AM on January 15, 2023

Response by poster: The additional power connector appears to have solved the problem! I will be back later to hand out Best Answers and comment further but first I have a build to complete....
posted by Busy Old Fool at 3:54 AM on January 15, 2023 [9 favorites]

Response by poster: OS successfully installed and a few games played; the next step will be to add a DVD drive, tidy the cables and figure out how LED lighting strips work. (Yes, this is being built for a child!)

My only consolation for not realising that since I last built a PC there is now an additional CPU power cable is that I was right in my instinct that I must be missing something fairly obvious.

It would be nice if the motherboard gave a more helpful error if a power cable isn't plugged in than "bad RAM" and the manual could have made the fact there were two power sockets clearer instead of giving them the same number on the layout overview. But in the end it was on me to read more and double-check everything.

I also should have taken the full PC in its case to the PC shop instead of just the motherboard, another lesson learned.

Thanks again to everyone who answered and especially those who identified the problem.
posted by Busy Old Fool at 3:36 PM on January 15, 2023 [3 favorites]