Question Need info on molex pcie risers for mining psu on how they take power "diagram" like

[JonasTechButchery]

So I would like to know does molex riser pcie consume power only from 12v and 5 v is for show or does it use /need/require both to be plugged in? I intend to retrofit a very expensive Silverstone modular 1300R PSU who's voltage has weakened on 5v compartment but 12v is perfect. The PSU will be converted to be pure 12v 6/8pins/molex and work as secondary PSU for dual PSU chained build mining/server type purpose.

But since molex has 5v pin that is what worries me. Do I need 2 gnd wires for pci riser molex to be safe to use or 1gnd is fine (2pin molex like one used for fans)

Can I do this on HP server breakoutboard too? It has 12v and GND area that's how it gives out all power. Solder 1 molex wire on 12 and one on GND and use for pci risers? or am I missing something like overheating, current resistance? IDK... thus I am asking if somebody could offer his deeper knowledge of this. Any additional intel means a lot. Thanks

Please don't even use word RMA if that was an option I would have done it. Every time I ask a question there is somebody telling me to RMA like I don't know how warranty works. RMA is not an option here. DIY or garbage. It's too expensive to throw away so DIY...

 

[Aeacus]

So I would like to know does molex riser pcie consume power only from 12v and 5 v is for show or does it use /need/require both to be plugged in?

GPU riser cards (be it vertical mount in gaming rig or mining rig), work only with 12V. 5V isn't needed at all.

Riser mounts can have two types of input power connectors, either 4-pin MOLEX (what you have) or 6/8-pin PCI-E. And in PCI-E, there is no 5V what-so-ever.

a very expensive Silverstone modular 1300R PSU

That is a joke. Sliverstone HELA 1300R is actually one of the cheapest 1.3kW units out there. At ~280 bucks, it doesn't get even close to the actual, very expensive 1.3kW units. E.g like these beauties,
pcpp: https://pcpartpicker.com/products/compare/4GyV3C,HyYmP6,hMCZxr,WrcgXL/

Just look what Seasonic units cost. Now, those are expensive. Also, best what money can buy as well, hence the price.

Do I need 2 gnd wires for pci riser molex to be safe to use or 1gnd is fine

One ground is fine IF you do not exceed the wattage capacity of 4-pin MOLEX cable. The 2nd ground is for 5V in 4-pin MOLEX cable.

2pin molex like one used for fans

If you use that, the cable wires are so thin, that it won't survive powering the riser. ~30W is what the 2-pin fan cable is capable of, since it is ever used only for up to 12W to power the case fans.

Solder 1 molex wire on 12 and one on GND and use for pci risers? or am I missing something like overheating, current resistance? IDK...

Ideally, you'd have one 4-pin MOLEX cable per riser. At most, you can get away with two risers per one 4-pin MOLEX cable. But if you plan to solder the 4-pin MOLEX cable longer with more connectors, e.g 6, to power all risers with just one MOLEX cable, you WILL melt the MOLEX cable.

4-pin MOLEX cable is rated up to 156W. One riser consumes 75W. So, MAX two risers per one cable (total 150W per one cable). Ideally, each riser has it's own cable coming from PSU.

E.g like this dual-PSU 6x GPU mining rig:

Direct link if image doesn't load: https://blogger.googleusercontent.c...WHLnwYiQG3tYRWE8ojNW49oTBo/s1600/powerrig.png

Please don't even use word RMA if that was an option I would have done it. Every time I ask a question there is somebody telling me to RMA like I don't know how warranty works. RMA is not an option here. DIY or garbage. It's too expensive to throw away so DIY...

I would've suggested new PSU instead, since your HELA R seems to be on it's way out. And if it's older than 5 years, then it's warranty is also expired (hence no RMA option). Also, it being one of the cheapest 1.3kW units, doesn't make it too expensive to throw away.
Now, if you'd have 500+ bucks Seasonic unit, then it would be different story. And even then, you could just RMA Seasonic unit since that one comes with 12 years of warranty.