advice before I fry myself

By thenamesbond · 30 replies
Mar 24, 2003
  1. Couple of questions regarding cooling :

    Firstly im obsessed ( its pushing on a geeky obsession as well ) about noise... I have now kitted computer out with silent(ish) case fans (3 of them) a zalaman heatsink and fan, and padded computer with magic fleece (sound proofing) ... I also have a nice new PSU because my other one packed in, the problem is the new PSU has noisy fans :rolleyes:

    Right I think! I will soon change that and purchase 2 more silent 80mm fans I rip open the PSU and get scissors and insulation tape on the ready for cutting out old fans and adding new fans... call me a wimp but i stopped and hence this post!

    Is it okay to just cut off the old fan wires and just tape in some new fans? (maybe solder if im feeling proffesional)

    Second Question :

    I have a large heatsink, and a fan that blows the heat from the heatsink all around my case... which i figure is a rather stupid way to cool things - overal system temperature rises, and everything gets hotter... so I get the following idea will it work? anybody tried it? any sites with info?

    remove heatsink fan, get 2 more case fans and connect to case so that they "extract air" run a pipe from both fans to either side of heatsink, creating a sucktion effect, which will draw heat away from heatsink, keep a constant flow of air over heatsink, and then get rid of the heat OUTSIDE the case... I would need a v.good fit around the actual fan, and a bendy pipe (maybe old hose but would need away of bringing size from fans (80mm) down to fit well over the hose... a trip to the DIY store will solve that problem im sure ;)

    well any comments suggestions welcome!
  2. acidosmosis

    acidosmosis TechSpot Chancellor Posts: 1,350

  3. acidosmosis

    acidosmosis TechSpot Chancellor Posts: 1,350

    Oh, and by the way. If your going to insist on opening up your power supply and cutting wires. I would REALLY suggest making sure the power is not hooked up to it ;-). Also I would let it sit for about 6 hours and hopefully it will lose some power. My dad is an electrician and I know monitors can hold power for a long time, and I would think power supplys do also. Just be careful if your going to touch anything inside the power supply and do yourself a favor and do a week or two of research on Google. I'd rather not hear about someone turning into a peice of instant bacon.
  4. Mictlantecuhtli

    Mictlantecuhtli TS Evangelist Posts: 4,345   +11

    I think fan ducts & filters actually increase the noise due to turbulence and resonance.
    Personally, I've changed my PSU fan to run at 7 volts instead of the default 12. Just be careful ;)
  5. thenamesbond

    thenamesbond TS Rookie Topic Starter

    ok I looked up a few sites on google, and they seem to think its okay to change the power supply fans, But i will take your advice and leave computer off overnight before i do anything with it.

    As for the fan duct I was just thinking about it as im sure it would bring system temperatures down a lot, and make for a lot more efficient cooling... But if it makes more noise ... :thefinger
  6. Nic

    Nic TechSpot Paladin Posts: 1,549

    Firstly, all computer power supply's are 'switch-mode' devices, and do not store energy after the power has been switched off. It will be quite safe to work on such a device just a few seconds after the input power is disconnected.

    Secondly, don't change your PSU fans unless you are certain that the new fans have at least the same rating. The PSU fans will have been specially rated and selected to suit your particular PSU.

    And Lastly, I feel that you are wasting your time trying to fit air ducts and using fans to suck air away from your heatsink. Not only is this solution inelegant, but I feel that it will also be less effective and may result in overheating of your cpu. I say this because when you create suction, any air in the vicinty will take the shortest route and exit through your fans. This may mean that vital cooling air does not reach the base of the cpu heatsink in order to cool it effectively. This is why ALL cpu fans blow air directly onto the base of the heatsink.

    If you are serious about removing hot air from your case, then fit additional case fans as everyone else does.;)
  7. Justin

    Justin TS Rookie Posts: 942

    Nic: That is not true. I am not entirely sure about the newer ATX PSUs but I know for a fact that older PSUs, including ATX, all stored a great deal of power... not enough to kill you or seriously harm you, but definately enough to give you a good shock.

    thenamesbond: I wouldn't be too worried. I have worked on PSUs many times before to replace fans or to repair them.. as long as you are careful you have nothing to worry about. Just remember to work in a safe environment, remain grounded, and if possible wear an anti-static wrist strap. Another note, if the PSU has a switch on the back, then keep it plugged in when working on it. If it does not have a switch on the back, then unplug it - Keeping it plugged in while having the rocker switch off ensures that it is grounded properly. This is also the scenario when working inside the computer itself - It's safer that way for a variety of reasons.

    What you might also consider, since you seem to be adamant about low noise, is to look into sidemount heatsinks for the PSU. I have done this before to create totally silent (fanless) machines.. sidemount heatsinks work great in certain situations, even moreso if you get a large (120mm, etc), very low speed fan (1000rpm). Almost zero audible noise and works fine, if you don't mind the extra heat.
  8. Nic

    Nic TechSpot Paladin Posts: 1,549

    SoulHarvester ...
    Nic: That is not true. I am not entirely sure about the newer ATX PSUs but I know for a fact that older PSUs, including ATX, all stored a great deal of power

    I beg to differ. I think you'll find that 'standard' linear power supplies, such as those found in most household appliances use capacitors to store charge and supply D.C. voltage to the device. However, 'switch-mode' power supplies only draw sufficient power to supply the attached load. They do contain capacitors (as well as inductors), but in this case these are simply used to smooth the switched voltage output to form D.C. voltage required by any attached device. Switch-mode PSU's will only draw sufficient current to supply that demanded by the attached load, and will not work without a load of some kind. They do not store charge, and any voltage present would soon be discharged through the inductors that form the output filter. I have worked on these devices without problem many times. Believe me, a few seconds, or a couple of minutes if you are paranoid, is all you need.

    if the PSU has a switch on the back, then keep it plugged in when working on it. If it does not have a switch on the back, then unplug it


    The advice you provide is good advice to avoid damaging any static sensitive devices when working on your PC, but not when working on your PSU. This is potentially VERY dangerous. Don't do it. It is feasible (but definitely NOT recommended) to keep your PSU plugged-in to the wall outlet for both cases, as long as you remember to switch the wall socket off. However, if you are just swapping fans on a PSU, which you will have removed from you case, I would be very surprised if you found any static sensitive devices present. Its true that the power transistors may be static sensitive, but as all components will be in circuit, and you will be unable to avoid contact with the PSU case, then you'll find it almost impossible to damage any components with static. There is NO need to have your PSU connected to the wall outlet at all, and in fact this would present you with a significant potential risk of electric shock. Also, although replacing fans will be easy, if the fans you select do not provide enough cooling, you WILL damage your PSU. Also if your PSU has a fan speed controller circuit, depending on its design, it may not work correctly with your chosen fans.

    sidemount heatsinks for the PSU

    I've never heard of these. Please explain how it would be possible to fit such a device to a PSU, which is probably a tight fit with the PC case. Also, how can internal PSU components possibly be cooled by such a device. Maybe you are talking about CPU heatsinks with side-mounted fans.

    I apologise, if I sound a little annoyed, but I believe I am qualified to provide the response I gave in my last post. It doesn't help anyone to provide contradictory, and clearly incorrect, and potentially very dangerous, counter argument. Please verify your facts before posting alternative ill considered dangerous advice. Thanks.
  9. acidosmosis

    acidosmosis TechSpot Chancellor Posts: 1,350

    hehe I started a war... note: just keep it low profile guys, the troops overseas are doing enough for all of us ;-)

    Just kidding :p
  10. Justin

    Justin TS Rookie Posts: 942

    My mistake about keeping it plugged in with the cover off. I was thinking of something entirely different. Yes, it is not a wise idea to keep it plugged in while working on the PSU.

    No offense, Nic, but I don't see how you are any more qualified then I or another here. I am an electrical engineer as well as a computer technician and I can guarantee you that older power supplies (Again, I haven't messed with any newer ATX power supply, ala 1997 onwards) will have a fair amount of power in them for quite some time before it is discharged.

    Sidemount heatsinks are common and I use them often. Typically they are quite thin, and are purchased in bulk on giant wafers which you can cut to spec. I don't know about your case, but inside most of mine there are large areas of the PSU exposed at all times that would have plenty of room for sidemounts, sometimes enough for all the way around, excluding the side it is mounted on.
  11. Nic

    Nic TechSpot Paladin Posts: 1,549

    Soul Harvester ...
    No offense, Nic, but I don't see how you are any more qualified then I or another here

    Well, before my current career (Software Engineer - I have an MSc in Software Engineering), I used to be an electronics developer working in the defense/avionics industry (where switch-mode supplies are the norm), so I know quite a lot about 'switch-mode' PSU's thankyou. Incidentally, I graduated with an honours degree in electronics way back in 1989. However, I am now unemployed yet again, and therefore spend a lot of time on the web (whilst retraining and waiting for the economy to recover).

    My comments still stand. However, maybe you have at some time been unlucky and worked on a very low quality, badly designed PSU, in which there may be some basis for your assumptions, but I personally have never encountered this.

    Please, supply a link to sidemount heatsinks if you can find one, which shouldn't be a problem if they are as common as you say. Maybe I am confused and not really understanding what it is you mean - in this case I apologise in advance.

    Also, it is NOT my intention to upset, nor offend, other forum members, as I am sure its good to be part of a community and provide assistance to others. If I am wrong then I will have no problems admitting it, and will have learned something new - We ALL make mistakes. But it is important that anyone providing advice that may put others at risk of injury, should be very careful before making such statements.

    Thats it for me. Enjoy!
  12. thenamesbond

    thenamesbond TS Rookie Topic Starter

    Okay well i figured electirc plugged in would be a bad idea anyway, I also wonder about earthing yourself while working on power supply ( and thus creating the shortest route for electric to earth right through your body?? )

    Anyway just for the record I avoided touching anything other than the fan cables and everythign went smoothly (in fact it was very easy)

    Just snip off the old fan wires , snip of the new fan connector and join the 2 wires (I couldnt find any 2 pin connectors that are used on power supplies so needed to recycle!)

    Just wondered what the yellow wire was on my new fans... i didnt use it, but I guess its for RPM monitoring (?)

    I can say that the change was a good one, the fans are temperature controlled and are nice and quite until the system gets hot.

    Another point i wanted to make is that adding extra case fans will not help my cooling! lots of people say this but i really cannot belive it will do anything, surely the optimum cooling is cold air in from the bottom, and exiting around the cpu / top area of case.
    Thus creating a nice steady flow of air in an "S" shape....
    I have tried adding another fan to test this theory on another computer and it just raised the system temperature by 3°C!

    I cannot take anymore air out from my case near the top (i have PSU extracting, and 2 case fans immediatly underneath the PSU)

    Im happy with my cooling now the system makes a nice silent Purrrrr, the cpu is overclocked by 150mhz (ish) and temperature is about 43° CPU and 44°C system

    One last thing I wanted to ask is about the fan protectors you put on, the one i uses tends to create a whooshing sound around it which stops when removed - obiously not having one is dangerous so anybody know of a good one that will help stop this (the one i have now has a flame cut into the metal so i guess isnt aerodynamic)
  13. Nic

    Nic TechSpot Paladin Posts: 1,549

    That whooshing noise is just turbulence, just as you said. A simple wire fan guard (like you find on good PSUs, etc.) is your best bet.

    Extra case fans WILL help your cooling, so long as they fitted in good locations, and are facing the right direction. Have all fans fitted on the front of the case sucking, and all fans fitted at the rear blowing. That is all fans will be pointing the same way to create a good laminar airflow (directional e.g. IN at front OUT at rear). Its not the 'S' shape thats important, but rather that air is not allowed to circulate around your case, and can exit quickly taking any heat collected with it. I'd be very surprised if your case temperatures increased with this layout. In the example you mentioned, the fan may have been fitted the wrong way around by mistake.

    PS: Its good to see you are aware of the dangers when messing with electricity, and won't be opening a PSU with potentially LIVE terminals inside. Some younger members might not realise this and follow any advice, even bad advice, with fatal consequences.
  14. Nic

    Nic TechSpot Paladin Posts: 1,549

    Girls like computers too

    Soul Harvester, am I correct in thinking that you are female?

    I hope you weren't offended by my comments, as its good to have women contribute on these forums. Please don't take any flak too seriously and stick around. ;)
  15. Justin

    Justin TS Rookie Posts: 942

    Nic: I haven't worked in engineering in quite some time, and again I am going off personal experience. I'm not saying you are wrong about current power supplies, but I assure you of the ones I have worked with, including computer PSUs, many have had capacitors, some of them typically in the 15uF+ range.

    I will take a picture of the heatsinks I am talking about tonight. All of mine I have purchased in bulk or received as surplus from companies such as APCON.
  16. Nic

    Nic TechSpot Paladin Posts: 1,549

    Soul Harvester, Thanks!
    I hope this means we can still be friends. :D

    A good tip to avoid conflict on forums is to provide a response (even contradictory response if you feel like it) without refering to another member's post. This allows others to make up their own minds what to believe, and avoids confrontation from telling someone they are wrong. No one likes being told they are wrong, especially when they strongly believe they are correct. If you are absolutely sure that some statement is incorrect then it might be a good idea to post a link to information supporting the claim.

    Yes, I believe you are correct in the fact that some PSU's have 15uF+ (i.e relatively large) capacitors fitted. The point about switch-mode PSU's is that these capacitors are used as *filters* to remove any unwanted spikes from the switched output voltage, and thus leave the remaining DC component of the output waveform. The spikes are due to AC components of various harmonic frequencies, with the pulse period determining the lowest AC frequency present. I'll stop now as I'm starting to sound too technical and boring. This is quite different to their use in linear PSU's (i.e. those fitted with transformers) which actually use capacitors to hold a charge (i.e. DC voltage) which can then be supplied to a regulator circuit for stable DC voltage output.

    You can verify the above by switching your PC OFF at the wall outlet. You'll find that it dies instantly, because no charge is stored. Try doing this with a TV set and you'll find that it fades to OFF because charge is still being supplied from the storage capacitors.

    You don't have to post any pictures of those heatsinks unless you really want to. I believe you, although I haven't heard of these before, and you'll probably find that the PC case to which the PSU is attached will act like a giant heatsink, so additional cooling is not necessary - other than for internal PSU components, which is where the fans come in.

    I did notice that your profile says you are a college student. What is it that you are studying now? You already mentioned that you are no longer in engineering.
  17. Justin

    Justin TS Rookie Posts: 942

    Computer Information Technology and Digital Electronics

    Though I have yet to take a single computer course (I tested out of many courses).

    I got A+ and MOUS more out of boredom then any real desire.
  18. Nic

    Nic TechSpot Paladin Posts: 1,549

    WOW, you're one seriously talented chick!:D

    Just remember and have *fun* with all that stuff you're learning and you'll walk the exams.;)

    Signing off ...
  19. Justin

    Justin TS Rookie Posts: 942

    MY life is nothing but fun. I've never had trouble with any class or any exam.. I am thinking of dropping computer tech after I get this degree and moving onto physics.. which is what I really love.

    OH and Nic, I'm not female. The line in the sig is at the insistence of my girlfriend.
  20. Arris

    Arris TS Evangelist Posts: 4,730   +379

    I thought I'd seen a picture or info at least that confirmed that Soul was a guy. Maybe I'm mixing people up. Just thought I would try and straighten that out ;)
  21. Nic

    Nic TechSpot Paladin Posts: 1,549

    OOPS, so sorry SH.:blush:

    It was all going so well too!:D

    Incidently, physics is also something I very much like, and its probably a wise move given that the IT sector is definitely not the place to be right now. That is, not if you aim to find work of any kind.

    I think I'll stop there now, before I dig myself into another, even deeper hole.:D

    PS: Maybe you should consider changing your sig, as many might now mistakenly think you are gay (hehe :grinthumb).
  22. Justin

    Justin TS Rookie Posts: 942

  23. Arris

    Arris TS Evangelist Posts: 4,730   +379

    Ah. Thats why I couldn't find pics in the Picture of yourself thread, because I saw the soulirl stuff before ;)
  24. Nic

    Nic TechSpot Paladin Posts: 1,549

    You've got your own retail outlet then SH! :grinthumb

    The lengths students need to go to just to get through college these days, well I never ... :p
  25. Justin

    Justin TS Rookie Posts: 942

    Yeah heh... most people are amazed at how quickly I burn through hardware... I roast probably two boards a week. I'm probably about to roast another... this tbird is running at 66 C when idle. Oh well, it will just give me an excuse to buy an AXP.
Topic Status:
Not open for further replies.

Similar Topics

Add your comment to this article

You need to be a member to leave a comment. Join thousands of tech enthusiasts and participate.
TechSpot Account You may also...