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HX 850 doesn't like the cosmos S case?


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First of all sorry for my english


I'm a recent owner of the HX 850 PSU and it seems it does not like the Coolermaster Cosmos S case.


The Cosmos S case got an ATX 24 pins extension which have to be connected between PSU and Motherboard. The ATX Extension doesn't have anything special (looks like ATX 20pin to 24 pins adapter) except 2 little wires on the MB connector for connecting the Power On "digital" switch.

Wires have connector for plugging them or not


You'll be able to see the connector here http://images3.hiboox.com/images/0808/yixebnkr.jpg


The connection looks like this :


Motherboard === ATX Extension == PSU


**************Wires for Power On Switch


(* are just here for the draw)



The issue :


When I plug the PSU on Mb WITHOUT ATX Extension : POST is ok

When I plug the ATX Extension between MB and PSU WITHOUT connecting the wires for power On switch : POST is ok

When I plug the ATX Extension between MB and PSU WITH wires for power On switch connected : POST is not ok and computer is rebooting during the POST.


I tried the "Wires plugged/unplugged" around 20-25times and results are exactly the same each time.


Before getting the HX850, i used a Seasonic M12 PSU which work perfectly without any reboot when Power switch wires are connected.


Any clue or tips to fix this?



Thank you

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  • Corsair Employees
I haven't seen a case work like that either. Have you tried to contact Coolermaster? There should be a way to connect the power on switch directly to the power_on on the motherboard.
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I haven't contacted CM because there is absolutely no problem when I use my seasonic PSU (M12 500W). Problem is only present with HX 850..


This special connector is also used because all of the connector have red LED...

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  • 3 weeks later...

I am having this exact same problem with the Cosmos S case and my new Corsair 850w modular PSU. If the power switch is connected to the motherboard and the adapter is between the 24pin and the motherboard then it always restarts before post. This did not happen with my previous "Hyper" power supply, nor a generic ****ty power supply I used to test.


If I use the motherboards buttons to start the machine(this can be done with the adapter still in place and the case switch disconnected) then it powers on fine, but as soon as I plug the power switch in to the motherboard it powers down instantly.


I don't think this a "fault" with either product just a quirk which means they don't inter-operate well. Is it possible you guys might know what the problem is psu end and perhaps come up with a hack that would get things working? I love both products and don't want to have to send the PSU back for another brand.

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  • 4 years later...

I have to bump this thread.


Has anyone found a solution for this problem? I have the AX860 PSU and a P8Z77-V PRO - Asus Mainboard.


If I plug the 24 pin adapter between the mainboard and the PSU the system won't boot.


Without the adapter and a extra power button the system works fine.

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