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#1
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Tentative experiments
Stephen Howard wrote:
Any learned bods care to give an opinion? My old Chaintech 6ATA2 board with its Celeron 466 chip are pretty much nearing the end of their days ( well, they work fine, but you know what I mean! ), and during a regular dust of the internals I decided to have a bash at overclocking the CPU and quietening the machine down. To this end I set the FSB to 75Mhz, resulting in the chip showing 525Mhz at boot. I then spun up a few fans I had lying about and found that a 24v power supply fan run at 12V is very quiet indeed. So I bunged it in the power supply, and orientated it to exhaust ( as normal ). For good measure I bunged another 24v fan in the rear of the case, and a larger 12v at the front - and made them switchable ( in case they were needed ). MbProbe reports the CPU running at 32 degrees centigrade when running Photoshop and Dreamweaver ( which is about as stressed as this machine gets ), and in two weeks running 9 hours a day there have been no problems with only the PSU and CPU fans operating ( and it's sooo much quieter ). MbProbe reports the Moboard as at least two degrees cooler than the CPU, and the case ten degrees. Can this be too good to last?? Not necessarily but there are a few risks in there. For one, 12 volts is below the guaranteed start voltage for a 24 volt fan so there is a chance that, some day, one of them just won't spin up when you turn it on. That's not so bad for the case fan as you can monitor case (or CPU) temp, and you have a second one, but it could be a serious problem if the one in the PSU fails to start. Btw, reverse the front and rear fans. It's better to have the stronger one in the rear plus front noise is easier to hear than rear noise so it'll sound a bit quieter if the noisy one is in the rear. The second risk is you've lowered the PSU airflow so it's not going to cool as well. You're probably getting away with it because it's not operating at full load but, since you aren't monitoring PSU temp, you don't really know. It's safer to use the 12 volt fans but, for quiet, on 7 volts (fan white molex plug ground [black wire] rewired to +5 [red]) as the typical guaranteed start voltage is 7. Although, for the PSU, I'd stay with the stock fan unless you can check temps to ensure you're not cooking it. |
#2
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On Tue, 29 Jul 2003 04:44:43 -0500, David Maynard
wrote: Not necessarily but there are a few risks in there. For one, 12 volts is below the guaranteed start voltage for a 24 volt fan so there is a chance that, some day, one of them just won't spin up when you turn it on. That's not so bad for the case fan as you can monitor case (or CPU) temp, and you have a second one, but it could be a serious problem if the one in the PSU fails to start. I noted that problem with one of the 24v fans - it refused to go without a bit of a nudge, and was cast aside in disgust. The current PSU fan ( 24v ), although quieter, makes a sufficiently audible whirr, which is enough to detect if it's operating - but I appreciate the warning. Will have a think about what I can do about that. Btw, reverse the front and rear fans. It's better to have the stronger one in the rear plus front noise is easier to hear than rear noise so it'll sound a bit quieter if the noisy one is in the rear. I haven't needed to run the case fans, not according to the temp. gauge, but I'll bear that advice in mind when I next open the case up. The second risk is you've lowered the PSU airflow so it's not going to cool as well. You're probably getting away with it because it's not operating at full load but, since you aren't monitoring PSU temp, you don't really know. An excellent point. What d'you reckon of the feasibility of bolting the large ( 6 inch? ) 12v fan to the underside of the PSU? I'd have to block the side vents I imagine. This would obviously blow case air through the PSU, but as the fan was held inside the case it should prove quieter ( plus it runs quieter than the standard 12v PSU fan anyway ). Would I be right in assuming that specially built quiet PSUs are fitted with slower fans, and built to work at higher operating temperatures? It's safer to use the 12 volt fans but, for quiet, on 7 volts (fan white molex plug ground [black wire] rewired to +5 [red]) as the typical guaranteed start voltage is 7. Although, for the PSU, I'd stay with the stock fan unless you can check temps to ensure you're not cooking it. That sounds ideal - but let me get this clear.... I leave the positive feed as is, remove the negative feed and rewire it to a positive 5v supply? The difference across the terminals would be what powers the fan at 7 volts? Might all sound a bit fussy, but other than the computer my working environment is completely silent - so any acoustic improvements I can make would be a bonus. Many thanks, -- Stephen Howard - Woodwind repairs & period restorations www.shwoodwind.co.uk Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk |
#3
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On Tue, 29 Jul 2003 19:07:01 -0500, David Maynard
wrote: Stephen Howard wrote: The current PSU fan ( 24v ), although quieter, makes a sufficiently audible whirr, which is enough to detect if it's operating - but I appreciate the warning. Will have a think about what I can do about that. Also note that it's starting might get more problematic as the fan ages and contamination, I.E. dust, could affect it more. Another good point - my workshop can get very dusty at times, hence my need to regularly clean out the 'puter. PSU fans are pulling case air anyway but the problem is in understanding the airflow inside the PSU. I.E. They don't just slap vents at random on them; they're designed to create the proper airflow through the various components with the stock fan and just how well something else tacked on would work isn't immediately obvious. I considered that - the PSU has internal vents on the bottom and on the side opposite the fan. I figured that a fan of sufficient 'oomph' would drive air right round the box if there was only one exit point. Of course, that depends whether incoming air from below has access to the top of the circuit board - I could even be better off bunging the fan on the side. Having said that, I have a number of PSUs knocking about, and quite a few of them only have vents on the side opposite the fan, which implies that cooling over the top of the circuitry is more important than below ( makes sense I guess ). Would I be right in assuming that specially built quiet PSUs are fitted with slower fans, and built to work at higher operating temperatures? There are a number of possibilities. One is, as you suggest, designing for higher temps but then one would potentially be using different components to accommodate the higher temps which, as but one example, might be a more efficient heatsink so that even though the overall PSU temp is higher the actual component temp isn't. Another trick is the 'sometimes noisy' temperature controlled fan approach. It runs a quiet low speed, unless you use the power where it speeds up to keep it cool. The controlled fan was what made me wonder just what these quieter PSUs actually contain. Seems you pay a premium for them, and if it's just a bit of jiggery-pokery with a fan..well... That sounds ideal - but let me get this clear.... I leave the positive feed as is, remove the negative feed and rewire it to a positive 5v supply? The difference across the terminals would be what powers the fan at 7 volts? Correct. Btw, that isn't a 'proper' engineering solution either as it doesn't do anything to ensure the 7 volt is really 7 volt. I.E. the 12 volt rail could be running a bit low, within spec, and the 5 volt could be running a bit high, within spec, and you wouldn't have 7 volts on the fan so *it* would be 'out of spec' but, in practice, the odds are better than starting with one 2 volts under spec to begin with (the 24 volt on 12 [which, as noted, could be running low]). snip Thanks for the further clarification - I can see the sense behind it. On my athlon I ducted the CPU heatsink to a single case fan in the rear which does double duty as case and CPU cooling. It works quite well, especially with the fan on 7 volt quiet mode. My next step was to duct the CPU to the bottom fan of the dual fan PSU (where the real noise now is) to cut another fan out but I haven't gotten around to that yet as the present solution is 'good enough'. If you want to mess around with PSU fans (like you hinted at above) you could consider using a large, slow RPM, fan in-between the CPU heatsink and PSU. snip Depends on just how much work you want to expend on it. Rewiring a few connectors doesn't take much. Sounds promising, thanks. There is one other possibility for me. I've toyed with the idea of mounting a fan outside the workshop and ducting in fresh air. This would mean I could use a mains powered drum fan - which would be very quiet ( as well as being outside the building ), but it would mean the 'puter would have to be fitted with ducts. Not too big a problem, it never gets moved and the existing fans could be made switchable. I would assume that the best arrangement would be to pump fresh air in at the bottom rear of the case and have it vent through the PSU as normal - and the mains powered fan could take a filter too ( wouldn't want any stray birds/cats/children caught up in the 'puter ). Might sound like overkill for the current setup, but I've got my eye on a new board and chip, which will no doubt require much more efficient cooling. Cheers, -- Stephen Howard - Woodwind repairs & period restorations www.shwoodwind.co.uk Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk |
#4
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On Thu, 31 Jul 2003 21:47:37 -0500, David Maynard
wrote: Sure, you could do that. Anything that moves the air appropriately through the things in need of cooling will work but a bottom front entry is better as that moves air from front to back and should cool everything in between whereas bottom rear will tend to hug the rear on it's way to the PSU. Ah, that would prove to be a bit messy - unless I knocked up some internal ducting.... I beginning to think I might be better off with a laptop - but where's the fun in that eh?? Regards, -- Stephen Howard - Woodwind repairs & period restorations www.shwoodwind.co.uk Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk |
#5
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Stephen Howard wrote:
On Thu, 31 Jul 2003 21:47:37 -0500, David Maynard wrote: Sure, you could do that. Anything that moves the air appropriately through the things in need of cooling will work but a bottom front entry is better as that moves air from front to back and should cool everything in between whereas bottom rear will tend to hug the rear on it's way to the PSU. Ah, that would prove to be a bit messy - unless I knocked up some internal ducting.... Might not be as hard as it seems, depending on the case. I mean, if you HAVE a 'bottom rear' entry (wondered about that when you said it) you just need to baffle it on in a bit. Ever see that clear plastic case cooling addon (I forget the name) that goes on the bottom front fan inlet and just ducts air to the bottom middle of the case? Same thing in reverse. I beginning to think I might be better off with a laptop - but where's the fun in that eh?? Hehe. Welcome to the wonderful world of engineering. Frankly, the 'external fan' seemed needlessly complex and a bit like overkill to me. I'd go with the internal fan and ducting, like I suggested, as I favor self contained systems. That or the 'simple' solution of putting the existing fans on 7 volts. Regards, |
#6
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On Sat, 02 Aug 2003 19:45:04 -0500, David Maynard
wrote: Stephen Howard wrote: Ah, that would prove to be a bit messy - unless I knocked up some internal ducting.... Might not be as hard as it seems, depending on the case. I mean, if you HAVE a 'bottom rear' entry (wondered about that when you said it) you just need to baffle it on in a bit. Ever see that clear plastic case cooling addon (I forget the name) that goes on the bottom front fan inlet and just ducts air to the bottom middle of the case? Same thing in reverse. I do have a bottom rear entry ( pause for giggles ), and plenty of space in the case to build a duct.... I beginning to think I might be better off with a laptop - but where's the fun in that eh?? Hehe. Welcome to the wonderful world of engineering. Frankly, the 'external fan' seemed needlessly complex and a bit like overkill to me. I'd go with the internal fan and ducting, like I suggested, as I favor self contained systems. That or the 'simple' solution of putting the existing fans on 7 volts. I shall experiment later with 7V across a 12V fan - though once I have the dosh for an upgrade my feeling is that a passive CPU cooler and a quality PSU would be a good place to start. Regards, -- Stephen Howard - Woodwind repairs & period restorations www.shwoodwind.co.uk Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk |
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