Replacing HX850 fan

joxang

Limp Gawd
Joined
Oct 30, 2010
Messages
279
I'm looking to replace the stock fan on my corsair hx850 for modding purposes (red led - I have my psu with the fan taking air from the inside of the case).

I've never so much as opened up a psu before, so I was wondering if it's a simple matter of unscrewing the fan, replacing it with a new 140mm, and plugging it into the same fan socket inside the psu?

Are there specific specs I need to look out for to not blow out the fan or result in a fried cpu? Fans I'm looking at include these:
http://www.kustompcs.co.uk/acatalog/info_8905.html
http://specialtech.co.uk/spshop/customer/product.php?productid=12711&cat=2006&page=1

Cheers :).
 

DarkStarr

Limp Gawd
Joined
Oct 25, 2010
Messages
267
It should be fine, the thing is if it does have a plug it wont be the same as a typical fan, just get one that uses about the same power.
 

Nickbaldwin86

2[H]4U
Joined
Nov 8, 2009
Messages
2,135
Yes it is simple but you most likely will need to cut the wires from the current fan and solder them to the replacement fan because I am sure they don't use a standard 3 pin plug, but you might get lucky.

I replaced the fans in an old PSU with Blue LED fans, it was quick and painless but I remember having to cut and solder the wires.

Also don't be rubbing the caps in there either they are still full of power even if you don't have it plugged in ;)
 
Joined
Oct 6, 2010
Messages
572
Big thing to remember...a power supply can hold onto a TON of current within the primary caps. So its necessary to completely discharge it before doing any work on the inside. I'm not kidding...there is enough juice in an UNPLUGGED power supply to kill you!
Remove the power cord and attempt to turn on the computer. It should flicker to life for a bit...which is enough to discharge the PSU. Otherwise, letting it sit for a couple days unplugged would probably do the trick. That said, you never know how long it takes those caps to discharge.

Another thing to remember is that sleeve bearing fans don't do well in power supplies. This is because of the horizontal position and the heat. So if you replace the fan with something cheap (sleeve bearing), be aware that the fan might not last all that long. That Enermax fan had a "twister" bearing...no clue how well that will hold up, or even what it is. Other one is sleeve bearing for sho...
Another pretty serious issue is starting voltage. IIRC, corsairs have a fan controller that starts around 3.7v. Many fans simply won't start at this voltage, and that might become an issue. Eventually the PSU will get hotter and ramp up the fan voltage , causing it to eventually start...but I'm not sure if that's an ideal solution or not.

I took apart my Corsair TX750, and the fan had a 2 pin connector on it, just like the one on this fan below.

Shouldn't be too hard to find if you have decent electronics stores in your area. Being in the UK...I'm not sure what your options are, but you can always splice the cables like the above poster suggested.
 

joxang

Limp Gawd
Joined
Oct 30, 2010
Messages
279
Thanks for all the advice!

Damn 3.7V is low, I'm not sure I know any 140mm fans that can start off from that voltage. Another option is to to route the fan connector out of the psu with all the other cables and power it via a fan controller or even straight from a molex connector.

Will the psu start if there's no fan connected internally?
 
Joined
Oct 6, 2010
Messages
572
That I couldn't tell ya, but it most likely will.

As for low volt starting...these are rated at 4v - http://www.purecoolpc.co.uk/buynow-...DX14-1200-140-mm-Fan-1200rpm-UV-Reactive.html
These start at 4v - http://www.google.com/products/cata...og_result&ct=result&resnum=3&ved=0CBoQ8wIwAg#
The Noise Blocker Silent pro series starts down to 3.5v.


You're looking for a specific color combination, and that's hard. That Evercool red scorpion seems like the ticket, if you can find it in the UK. Not sure what bearing it uses...pretty sure its a "long life" sleeve. Not ideal for a horizontal orientation, but if you fab up and external RPM connector, you should be able to monitor it. Basically, the yellow wire on the fan is the RPM sense wire. Disconnect the black and red for wirring into the PSU, but leave the original 3 pin lead attached to the yellow wire. Route this outside the PSU and plug into one of your motherboard fan headers. Will allow you to watch the RPM of the PSU fan so you can spot it when it dies!



The rest of that
 

plugwash

[H]ard|Gawd
Joined
Sep 17, 2010
Messages
1,542
Big thing to remember...a power supply can hold onto a TON of current within the primary caps. So its necessary to completely discharge it before doing any work on the inside. I'm not kidding...there is enough juice in an UNPLUGGED power supply to kill you!
Seems highly unlikely to me, the highest voltage that caps will be charged to in a PSU is about 300V (probablly lower with a modern input stage) and it's high current circuitry so I doubt they will stay charged for long.

It's high voltage low current circuitry like CRTs that you really have to worry about the capacitors in.
 
Joined
Jan 7, 2011
Messages
36
Most power supplies above the white-box level will also have a bleed resistor across the primary caps to discharge them when the unit is turned off. I've messed with 400W+ power supplies mere minutes after they've been turned off, and check the voltage between the leads of the primary caps and it's generally only a trace voltage, 0.05V, and that's gone in a millisecond with the resistance from the DMM leads.

And touching the top of a capacitor isn't going to shock you (maybe if it's fully charged, I dunno), it's the leads at the base that carry current, not the aluminum cap. You'd have to reach down and start messing with the leads, or the underside of the PCB, to get shocked.


You should still be cautious, of course, but you don't have to wait fifty hours before opening up a power supply or you DIE or something.

I haven't tested scientifically... But I highly doubt that any PSU above the level of a Leadman could retain enough charge to be lethal after maybe 30 seconds at most, maybe a minute or two once you reach the 1kW level.
 
Last edited:

Gabriel5

n00b
Joined
Sep 27, 2009
Messages
31
OP would probably be wise to heed advice in this thread.
We can all agree that an open power supply should be approached cautiously, and that there is the potential to do serious damage.

Wish Redbeard were here. Or Jonny Guru?
 
Joined
Jan 7, 2011
Messages
36
According to 370ForLife from the JonnyGURU forums, who generally knows his stuff, a PSU's primary charge capacitors don't hold a charge for very long after the PSU is turned off, they discharge in seconds. It's the X capacitors that can potentially hold charge for a very long time.

However, even then, when you look at virtually any power supply you'll see two or three moderately hefty resistors on the primary side, and these are the bleed resistors to discharge those X capacitors. Every power supply I've ever opened, even the white box hunk-a-junk trashy Linkworld LPJ2 unit, had at least one bleed resistor present.

And again, X capacitors (the ones that retain a dangerous charge long term) are only conductive on their leads, you can touch the top of an X cap when it's fully charged with no ill affects--though touching the leads on the other side of the PCB may kill you. But recall that the bleed resistors ensure that these capacitors are discharged within bare minutes or even seconds of the PSU being shut down and unplugged.



So again, a degree of caution is not unwarranted when opening a power supply even when it's been shut down and unplugged, but it's not going to kill you if you don't wait a week before opening it.

However, always unplug the power supply, the controller circuitry and/or +5VSB circuit may be active when the PSU is plugged in, and you can receive a dangerous shock from that. And never mess with a power supply while it's running. Ever.
 

Skoobs

Weaksauce
Joined
Oct 4, 2010
Messages
90
could you maybe hook the fan up directly to the rear end of one of the 12v molex connectors coming out of it? ...like on the inside of the PSU?
 

Direfox

[H]ard|Gawd
Joined
Oct 24, 2004
Messages
1,945
OP, first thing is make sure you run that PSU for awhile if you haven't already because you are voiding the warranty (as mentioned above). Second, have you considered modding the existing fan with UV reactive paint? You might even be able to do it without cutting any wires.
 

skorpien

n00b
Joined
Jun 13, 2011
Messages
11
Was sleeving my HX850 so I decided to open her up (warranty's void anyhow) and post some pics.







It's a Yate Loon 140mm 2800rpm 140cfm 0.7A 12V fan based on Yate Loon's own product page:
http://www.yateloon.com/detail/38839/38839.html

It's also got a 2 pin fan header, so a regular case fan won't work without some modding.
 
Top