Have I done something dangerous? (PSU mod)

linden_arden · Post by **linden_arden** » Tue Mar 01, 2005 9:33 am

Ok, I am a quiet computing newb and recently modified my PSU. I didn't do much research before hand and things seem to be working ok for now, but I thought I would post here to make sure I am not going to set my house on fire or something.

Took the stock PSU from a used Emachine I bought. Opened up the PSU and cut the 80mm fan out (cut the two wires connected to the PCB in the PSU). I connected the original fan wires of the PCB and wired them to a male 3 pin fan connector. This connector goes into a Zalman fanmate control (which actually resides outside of the PSU case). I put a new 80mm fan in the PSU and connected it to the Fanmate. Thus, a speed controlled PSU fan.

Like I said, the thing runs, but have I done something dangerous? I know zip about eletrical wiring, etc, so maybe I have. Hopefully some smart folks can let me know.

sthayashi · Post by **sthayashi** » Tue Mar 01, 2005 9:49 am

That's a tough call.

When you modify an unknown power supply, you're taking a risk in my opinion, particularly if it was running rather warm before.

From your description of what you've done, it sounds like the normal electrical aspects are more or less safe, assuming there is no exposed wiring in the PSU. It doesn't take much to short something.

But you won't cause a fire from your direct work with fan modding. You're looking at 12V at relatively low currents there. It's the indirect effects of modding your PSU that I would be far more worried about.

tay · Post by **tay** » Tue Mar 01, 2005 10:21 am

I know this sounds silly, but put your face behind the PSU exhaust. If the air being blown out while at load (whatever your max load is) is more than just warm you may have to turn the fan speed up.

Make sure you snip out or open up any grills that you can to improve airflow (for example you can open up your intake grills by bending them with pliers so their surface area in the direction of airflow is reduced).

I've run several PSUs at very low fan speeds without a problem (5-7 volts) but I make sure the exhaust is not more than warm. As sthayashi mentioned if your system draws moderate power you should be fine. Also use electrical tape and heatshrink liberally to make sure you don t run the risk of shorting anything.

linden_arden · Post by **linden_arden** » Tue Mar 01, 2005 10:38 am

Thanks for the tips. I'll double check the wiring to make sure nothing is exposed.

Follow-ups:
1) If the PSU shorts, is the damage going to be confined to the PSU or are the mobo/CPU/disks in danger too?

2) If the PSU overheats, whats the extent of the damage going to be?

I've got a tinge of nervousness because I left the rig running while I am at work... Maybe I got a little too comfortable with my first mod! I did turn the fans all the way up before I left.

ChristianN · Post by **ChristianN** » Tue Mar 01, 2005 11:59 am

linden_arden wrote:
2) If the PSU overheats, whats the extent of the damage going to be?

I had a PSU go "Pfsssssssst-ngh!" on me once. If my memory serves me correct, it was an Aopen 300w psu (from the hx08 maxi tower from Back Then) that had its fan removed in the name of silence (..).

That unit worked for suprisingly many years with more or less no ill effects. The whole computer ran increcibly hot but was stable. The hardware, except from the now-dead Aopen PSU. No other hardware was hurt.

Now, this is a "mod" I cant really say I recomend, but in all honesty, it worked fine, box was stable, no hardware worth mentioning died and it was quiet. You have to work quite hard to get a fire doing something like this but it's fully possible. It's probably also wise to mention that I actually know what I'm doing when playing with this stuff; it was a weighted decision - fire risk vs silence

.

ChristianN · Post by **ChristianN** » Tue Mar 01, 2005 12:02 pm

linden_arden wrote:
1) If the PSU shorts, is the damage going to be confined to the PSU or are the mobo/CPU/disks in danger too?

Duh forgot to answer this one.

Shouldnt, but could.

All PSUs should have a shortcircuit protection that'll make sure nothing bad actually happens if you where to get a short. However, if this circuitry fails and you suddenly have a short on your 12v rail you'll have some bad stuff going down. Theres more then enough amperage on the rail to make wires litteraly glow red with all the problems that can cause.

Now, with all the disclaimers and theoretical horror stories, in reality this shouldnt actually be a problem.

luggage · Post by **luggage** » Tue Mar 01, 2005 12:20 pm

Depending on your country you may also lose any insurance claim in case of fire if you have openend a psu or the like