[SOLVED] Computer won't boot with two separate Lian li SP750 PSUs, but other PSUs work fine ?

Dec 6, 2022
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New build, i7 10700kf, rtx 2070, Msi z590 force. In a lian case which requires Sfx psu.

Stuck the lian li sp750 in there, and when I flicked the actual switch on the psu, the fans in my case twitched once, keyboard lit up for a split second as well, then nothing, and power switch on pc did nothing.

tried a totally different psu that was 650 watts, (atx so I just had it sitting in the desk beside comp) and it worked totally fine. Did the same with a different 750 watt one

got the store to get me a replacement lian li sp750. Put it in there, EXACT same result as the first sp750. And yes I’ve checked all connections etc, like I said the other psu worked fine.

mind boggled?? What am I missing here xD
 

Darkbreeze

Retired Mod
So, what store?

I'd say maybe they got a batch of bad power supplies from Lian Li. That or there is some kind of grounding issue regarding the motherboard and standoffs, and it isn't happening with the other units as they are not being attached to the case. Kind of reaching there but if the only difference is that the ones that work are being installed IN the case, screwed to it, and the others are not, then it's got to be related somehow. Too long of screws attaching the PSU to the case or something?

Have you tried the SFX units sitting on the case beside the computer like you did with the other ones?
 
Reactions: Dark Lord of Tech
Dec 6, 2022
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Yes actually I did try the most recent sp750 sitting on the desk beside the case just to see. Same result. This store only has the one in stock, so they ordered me the replacement from a different city. Seems unlikely that it’s a bad batch issue..
I am using some sleeved cable extensions, I don’t know if it’s possible that these Lian li units don’t like the extensions for some reason?

Like I said when I flick the switch on the psu, THAT is when the fan twitch happens, and then the power switch on the case does nothing. But the twitch happens every single time flick I the psu switch on. It’s almost like the psu is instantly powering itself down completely whenever i flick it’s switch on? I dunno man
 
Dec 6, 2022
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Removed the extensions and it works fine, with the sp750 in the case. So the lian li units definitely just don’t like these cable extensions. It’s odd to me that my other PSU’s worked totally fine with the extensions tho.. any ideas why? These regular cables from the lian li unit look butt ugly in here so I’d like to be able to use extensions if it all possible xD.
 
Dec 6, 2022
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I do in fact care about aesthetics, and the standard cables for the psu leave little to be desired. I was under the impression that extensions shouldn’t have any compatibility issues since they are merely extensions off of the original psu cables. As I said they worked fine with my other evga and cooler master psu’s that I tried.
 

Darkbreeze

Retired Mod
I mean, the proof is in the pudding I guess. The PSU doesn't work with the sleeved cables but works without them, not much else to determine there. Doesn't really matter WHY? They don't, and that's all that matters. So you are left with pretty much don't use sleeved cables with that PSU, or get a different SFX power supply, or get different maybe better quality extensions.

What brand are those extensions?
 
Dec 6, 2022
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They are EZDIY-fab. Budget brand, but reliable for me so far with case fans and such. I just found it strange that they worked no problem with a couple other units but not the lian li one specifically. And also Lian Li has their own rgb strimer extensions so I would hope their psu would work with those xD.
Anyway is what it is, I’m looking at some custom cables now as opposed to extensions.
 
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Darkbreeze

Retired Mod
Just make sure of a couple of things.

If the old cables have inline caps, you MIGHT want to check into whether that unit still has good enough ripple suppression if the new cables don't, and very often custom sleeved cables do NOT have the inline caps that the original ones had and this can affect the unit's performance when it comes to ripple. EVGA G2 (And many others) had this problem. In which case extensions might be a better option.

If the original cables do not have inline caps then it's irrelevant. Often the little extra ripple suppression from those inline caps isn't enough to worry about anyhow but sometimes it might be.

Another thing to note is whether the custom cables use the same or better gauge wiring than the original ones. I've seen quite a few that used smaller gauge wiring and that is definitely not desirable. Coming from Lian Li you'd HOPE that wasn't the case but I'd make sure anyhow.
 
Dec 6, 2022
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How would I find out if they have inline caps?

The custom cables I’m looking at are from an Etsy seller with a full 5 star rating on 2100+ reviews, who does custom cables. He requires you to tell him exactly what model of psu they’re for and everything.
 
Dec 6, 2022
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They do have braided cables, but unfortunately all of the wires are set up in a fashion that is rather twisted and tangly. Don’t come with combs, and even if they did I highly doubt one could get them to look good.
 

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