I have brand new Super Flower Leadex Titanium 1600W 80+ Titanium SF-1600F14HT power supply.
& have following observation, when I tried to replace a previously dead power supply.
I find that WITHOUT the AC power cable connected to the SMPS, the cooling fan in the SMPS spins & I can feel the breeze, it is like magic.
Some how power is coming back in REVERSE from the motherboard to the SMPS.
The only SMPS cable connected to the mother board is the 24 pin one.
I am yet to connect the rest of the SMPS cables …like the 4pin for CPU & others
It stopped when I disconnected the monitor’s miniDP<–>HDMI cable, from the graphics card.
Monitor : Samsung 32" space saving monitor S32R750UEN / LS32R750UENXZA
Graphics Card: XFX RX-570P8DFD6 Radeon RX 570
Motherboard: Asus P8H61-M LE/CSM R2.0 Micro ATX LGA1155
Monitor to Graphics Card cable : AmazonBasics Mini DisplayPort to HDMI Display Adapter Cable - 15 Feet
I am not sure which component is allowing power from the miniDP port of the monitor, to passthrough into the SMPS
Can you help me understand what is going on ??
To summarize, power appears to come in this flow
Samsung Monitor->mini dp–hdmi cable-> XFX GPU->Motherboard->24pin ATX cable → SMPS->SMPS fan.
Irrespective of the mobo, monitor etc, should not the Super Flower power supply have some sort of reverse voltage protection ??
Is the design of the power supply flawed ??
Mini-dp can deliver a current on pin 20. That is not used on DP-DP cables but mini-dp uses that pin and your GPU might allow that current to run through your system.
That was a known issue with bad dp cables in the past, which did not properly implement the vesa standard for dp cables. You might be facing that issue here.
I tried with a HDMI-to-HDMI cable from the monitor’s HDMI port, to the HDMI port of the GPU…
In this case, I do not see the SMPS fan spinning issue.
Nevertheless, as a device whose prime focus is on power handling, don’t you think that the SMPS should have had protections designed to handle such scenarios ? …I mean accepting into it externally generated current, via the DC pins & then using that to run the SMPS’s own cooling fan, appears to be a bit weird.
I now learn that there is this issue called the “Display port pin 20 problem”
Probably the Amazon basics cable I used is not compliant. The cable is 15 feet long & wondering if it has some active circuitry on the HDMI side, as that part is a bit bulky…
mini-dp should deliever a current on that pin, so i wouldn´t blame the monitor or cable.
Also its not really the job of psu to work around that issue.
I would blame the GPU, that one should block out that current.
Because that happened with multiple amd and nvidia models, from different vendors, im unsure if amd or xfx screwed that implementation in your case.
I have that exact same power supply. It powered my Threadripper 7975wx for about 6 months before one day I heard a gunshot like sound and the power supply completely died. Thankfully it didn’t perceptibly hurt any of the attached equipment. But I’m staying away from SF from now on.
As far as the “magic” fan, okay, it stopped when you unplugged the MiniDP-HDMI cable. But if you plug that back in, does it start again?
Because you may just be running into the reason that everyone wisely advises NEVER to open up or work on the guts of any PSU. Because they can retain a charge - even a deadly charge - long long after they’ve been disconnected from AC power.
It may just be a coincidence that it ran out of that juice when you unplugged the MiniDP cable.