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Help with Corsair RM850i Power Supply

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Joined: 5 months ago
Posts: 1
Topic starter  

Want to build a bench power supply with this Corsair RM850i. 


Can't even turn it on.  This one have type 4 connector.  I have the pinout for the connectors and the PS_On (green) was connected to Ground.  The unit was verified working before my son gave it to me.  I have successfully done this with an older ATX power supply.

One thing I noticed is that the PS_On is only 2.4v.  Standby voltage is good (5v).


Has anyone used Corsair before?


I refer to the diagrams in the page below (you'll need to scroll down because there is a second image in the page).


Thank you.

Workshop Guru Admin
Joined: 5 years ago
Posts: 1043

Welcome to the forum Dennis! 

Just bumping your post up, as I missed it earlier for approval - sorry about that!  I'm sure someone can assist you with the power supply, it sounds like it's probably something simple like an additional pin that needs to be grounded. 

If you or your son have access to the computer this was originally used in, you might be able to check the wiring with a multimeter.



"Never trust a computer you can’t throw out a window." — Steve Wozniak

Father of a miniature Wookie
Joined: 3 years ago
Posts: 6530

@dennisc Tie PS-ON to ground (normally a green wire, and either pin 14 or 16 depending on the connector) . Meter 5V Standby (normally purple, pin 9) and if it has 5V then check Power Good (normally grey pin 8) and it should have +5V. .If both pins 8 and 9 are 5V the PSU is working, if either or both are not it is broken. Let us know what you see.

The +2.4V on PS-ON is not normal AFAIK, that could mean either your pinout is different or something is broke. What colour is the pin you think is PS-ON?

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