Modifying a Q-Tec PSU

larsrenne · Post by **larsrenne** » Sun May 25, 2003 10:25 am

I'm planning to mod my cheap (GBP £22) 350W Q-Tec PSU (note that's http://www.qtec.info, not http://www.quietpc.com) but wanted to pick a few brains first

(so thanks in advance!)

I've already removed the stamped-out grill and have identified that the single 80mm fan it uses is a Power Logic PL80S12M (sleeve-bearing) model. After Googling for a bit the specs seem to be:

28.3dBA
2,500 RPM
27.55 CFM

It's attached to the PSU's PCB using a 2-pin connector (so no solder) and my plan is to do a straight swap (e.g. no undervolting) for a Panaflo L1A. I'm hoping this will cut the noise down to an acceptable level for me.

Since the Panaflo L1A is 1,900 RPM and 24 CFM I'm guessing it will have little or no impact on the safety and lifetime of the PSU, since I'll only be losing 2.55 CFM. So my question is: have I made a valid assumption or is my guess totally wrong?

Any and all thoughts welcome (including off-the-shelf quiet PSU ones)

dukla2000 · Post by **dukla2000** » Sun May 25, 2003 12:55 pm

That is pretty much a straight swap - don't know if you also saw Mike's article?

First word of warning I would add: check carefully which pin is +ve: on a Mercury/cheapo psu I have, the psu board fan header pin orientation is opposite to normal. (No big deal as everything can be swapped ...)

Second, what other case ventilation do you have? If your case ventilation is good then my personal view would be to go even slower/quieter than an L1A, perhaps to the NMB Dorothy sells.

Last - make sure air can get into the psu: either do the '90 degree twist' on the intake vents (somewhere else on this site) or remove them completely.

larsrenne · Post by **larsrenne** » Sun May 25, 2003 2:28 pm

Thanks for the reply and warning, I'll make sure to check and see that the fan is spinning before leaving it!

I've read Mike's article before but your link to it just reminded me of something else...has anybody tried using those spade connectors you get (usually with a crimping tool of some sort)? I think they are used in automotive electronics quite often, I know I used them when building a camper from a van and a caravan (not for me, for my Dad, I hate mobile homes of any kind...but that's another story

) You can get them in Wilkinson's for less than 3 quid and if you just snipped the wires above the PCB connector and before the header on the fan you could use the spade connectors to connect your new fan. Just a thought...

I have no other case ventilation which worries me a tad...there is no way to add any case fans to this case except for one 80mm case fan space right down at the bottom front part of the case, which I reckon won't help the PSU any, since it sits right above the CPU and draws in it's hot air.

The PSU has almost no air intake at all, so I'll do the 90 degree thing as soon as I buy/borrow a pair of pliers (small flat, no room for many tools of my own

)...or I could just take them out altogether as you said.

I think I'd feel safer with the higher volume Panaflo for a bit before I try the NMB...although I might get both just to play about with. I could always use the NMB as a case fan, even though (due to the layout mentioned above) it might not benefit greatly.

Post by **MikeC** » Sun May 25, 2003 2:35 pm

Here's a simple question: do you know what voltage is going to the PSU fan? If less than 12V, you're in luck, the Panaflo will give you very low noise levels. 28 dBA is not bad for a generic PSU fan. I guess the quality of the noise could be bad, tho.

larsrenne · Post by **larsrenne** » Sun May 25, 2003 2:42 pm

Hiya Mike, great site! The current (Power Logic) fan uses 12V, 0.14A. Would you say I would benefit any from having the Panaflo at 12V? Or would it only really be an improvement if undervolted?

Funnily enough, a friend came round to my flat a couple of weeks back and remarked how quiet (!) this PSU was compared to his.

I guess my problem is that my last PC was a Celeron 333a (new one is an Athlon XP 2000+) and used a 200/250W PSU, which had a fan that rarely even kicked in, most of the time it wasn't even turning. So I've been spoiled all this time

Kostik · Post by **Kostik** » Sun May 25, 2003 2:56 pm

Your PSU's fan is temp-controled, which means the PSU doesn't feed the fan 12v all the time, but only when it gets hot (so most of the time, the fan will spin slower and be quieter). That's why you don't need to undervolt the panaflo, and that's also why MikeC is wondering what exact voltage the PSU feeds the fan

I think this psu will probably be very quiet when you swap the fan for the panaflo. By the way, it's not very expensive, I wish I could buy one in France

. No, no, no I don't. I HAVE to stop buying stuff

dukla2000 · Post by **dukla2000** » Sun May 25, 2003 3:54 pm

larsrenne wrote:has anybody tried using those spade connectors you get (usually with a crimping tool of some sort)?

Most of the time I just use terminal blocks (e.g. part # FE78K at Maplin. Every time I get too neat and solder on 3- (or 2-) pin connectors, it seems later that day I need to play again with some other way of feeding the voltage. Terminal blocks make changes pretty easy and if you put a block of 4 across a disk power cable you have easy access to 12, 7 & 5V.

energy · Post by **energy** » Sun May 25, 2003 5:22 pm

Since you removed the stamped grille you will probably get around the same amount of air exhausted as with the original fan, but with much reduced noise levels (quieter fan and no obstructive grille). So no overheating problems.

larsrenne · Post by **larsrenne** » Mon May 26, 2003 12:57 am

Thanks for all the feedback guys!

energy: cheers, that's what I'm hoping. With the old fan still in place (I haven't bought the Panaflo yet) removing the stamped grille hasn't seemed to make it much quieter, I think this fan is just too loud.

dukla2000: nice idea about the terminal blocks, I hadn't thought of that. They would indeed be easier to fiddle with than spade connectors. Looks like a quick visit to Maplins may be in order

Kostik: yes, this PSU starts off by running the fan at a lower voltage and it's easily quiet enough for me (but by no means silent) at this level. The problem is of course (as MikeC points out in one of his articles) that after a period of time (about 15 minutes for me) the PSU warms up and the voltage to the fan is then increased. It never slows down once it speeds up either, it's a one-way thing

When you say it's not very expensive, do you mean the PSU or the Panaflo L1A? I can buy the PSU for less than GBP £20 (EUR28) and the Panaflo for less than GBP £8 (EUR11), both prices including VAT @ 17.5%. I certainly couldn't recommend this PSU based on noise.

I'm now wondering whether there is a connection between Q-Tec and Macron as when I opened up the PSU the PCB had "Macron ATX Power Supply" or something along those lines written on it. For a cheap PSU it doesn't look much different inside (e.g. heatsinks, layout, components) from the pictures I have seen of expensive ones.