Taking the cover off the PSU, recommended?

djhardkhor · Post by **djhardkhor** » Mon Nov 03, 2003 6:24 am

Hi

First post to forums! They are a great resource, as I have just taken the first steps in building a silent system.

I'm currently trying to silence a fileserver for my lounge. It's a juice-hungry 1ghz athlon B, with 1 low speed 80mm panaflo @7V as case exhaust. The box has an old 250W OMNI psu in it. The fan recently died, so I swapped in an 80mm Panaflo, undervolted as well.

The problem is that the psu only had a couple of little vents on the forward-facing side of the psu box, which sit directly in front of the heatsink setup cooling the mosfets (or whatever they are). The rationale probably being that air would flow into the psu, directly over the heatsinks, and then exhausted through the rear.

I recently took off the cover of the psu, to induce airflow thru the psu exhaust. However, I'm worried that this might actually be detrimental to airflow across the psu heatsinks, as air can get out around the heatsinks now.

I've got a thermistor on the psu exhaust, which has risen 2C, but overall motherboard and cpu temps hav dropped 2C idling. Haven't taxed the system yet; kind of scared.

What do you guys think? Will my PSU die a thermal death due to the new airflow pattern?

Thanks for your reading.

energy · Post by **energy** » Tue Nov 04, 2003 11:29 am

You will get better cooling with the PSU cover on. If needed, increase the size of the holes on the front of the PSU by either opening up extra ones, or by twisting the "bars" 90 degrees to open up more space. This should help PSU and case temperatures while reducing noise.

djhardkhor · Post by **djhardkhor** » Tue Nov 04, 2003 4:03 pm

thanks for the tip. Is this common knowledge? Or merely common sense (there has to be a cover for a reason!).

Will try it out tonight. Also realised that my temp probe is fixable, so I'll attach it to one of the heatsinks and see what happens.

ez2remember · Post by **ez2remember** » Tue Nov 04, 2003 4:42 pm

Read this article it talks about the removing of the cover and how it effects airflow and temps.

Running a PSU without a fan?

Removing the cover, also removes directed + concentrated airflow through the PSU components. It actually makes cooling worse with the cover off.

People add ducts to aid direction/concentration of airflow so it cools better.

djhardkhor · Post by **djhardkhor** » Tue Nov 04, 2003 5:18 pm

Oh,

I've been to this site for months, and thought I'd read most of the stuff on it! I feel so stupid, thanks for your time, guys - really appreciate it.

Mastiff · Post by **Mastiff** » Sat Nov 15, 2003 3:15 pm

Actually I would say that it's not as straight forward as the experts say. I have one PowerMan PSU on my HTPC in the Cinema Inferno Home Theater (you can see it on my website) and first did the standard modding by removing the bars to make the intake and exhaust holes more open. Wasn't really satisfied with the result, so I popped the cover. This PSU has a Papst 12 db fan I have pu in it, so it's pretty (actually very) quiet. Running without the cover lowered the CPU temp with about 5 degrees, it's now 40 at idle (XP2600+) and 50 at full speed. This is with a Zalman flower cooler and a fanmate on the fan, so it's probably not running much more than 5 volts. The motherboard temperature is around 32 degrees. This is in a 20 degrees room. The heatsinks on the fan still are warm hot to touch, but not so hot that I can't keep the finger on them. This to me says that it's not running too hot.

Oh, I have two blowholes at the top, but those fans run at a very low RPM.

larrymoencurly · Post by **larrymoencurly** » Tue Nov 18, 2003 3:24 am

When I tried my 300W Antec SmartPower with the cover removed, the low voltage heatsink eventually heated to 70 Celcius, but when I put a temporary plastic cover on to take the temp., the heatsink was only about 43C. To me this shows just how important the "tunnel" effect is for the PSU. OTOH the case interior dropped a few degrees, and the exhaust air was cooler and seemed to blow harder. BTW, don't touch the high voltage heatsink since it may have dangerous high voltage on it. This was true of my SmartPower, PowMax, and Delta PSUs.

Mastiff · Post by **Mastiff** » Tue Nov 18, 2003 4:24 am

Well, I turned off the pc very fast and felt the heatsinks. One of them was maybe 30 degrees, the other one probably no more than 45-50. And I'm a pussycat when it comes to heat, my wife always taunts me that I need to use a spoon to touch eggs that has been removed from the boiling water... On the other hand this is with the case fans, and with the temps I'm having now (33 case, 34 CPU idle, 40/44 load - and this is with a Zalman flower cooler, 120 mm Enermax fan on pretty slow speed) I might put the cover back on. No need to have it off with those fantastic temps.

djhardkhor · Post by **djhardkhor** » Tue Nov 18, 2003 5:23 am

Thanks for the replies guys.

I've stuck the lid back on the PSU. Reading that article about the Enermax PSU, and the comments here convinced me pretty quick. Opened the vents on the PSU, which seems to aid airflow a lot. Motherboard temps went back up, though. I suppose I'll deal with it!

I've also repositioned the motherboard sensor on one of the voltage regulation heatsinks on the PSU - without touching them. With the sensor in between two fins on the heatsink in the PSU, the temps read now high sixties after boot, and top out at ***79*** centigrade under load! Could be a sensor problem, I suppose, but then, I read on the forums that the bits in a PSU are probably rated at over 100C anyway.

So, I'll probably keep the old OMNI with the 7V Panaflo 80L1A as it is. Recently replaced heatsink with an Aero7+, and am contemplating swapping my other panaflo for the blower. Temps @ lowest speed is now about 52/58 (idle/load) with a Panaflo @7V as exhaust (plus PSU), which is hot compared to newer (non-T-bird) setups. I've got an old KT133 board which needs some soldering mojo to fiddle with the voltage settings, I think (Asus A7V).

Can't wait to upgrade.

Thanks again guys

djhk