View Full Version : Power Supply taking a digger ?

02-05-04, 10:59 PM
I had something really strange happen tonight and maybe someone can give me some insight into what it might be.

I just finished installing a Radeon 9800 Pro and one of the fan leads on my Asus P4P800 up and died. (As far as I can tell). I had a fan connected to it before and now it'sa dead. I tried a different fan but it's like there's no power to the lead on the mobo. Well I was dinking around trying to connect the fan to a couple different leads and my computer shut down and wouldn't restart ! I had power to the motherboard and checked all the power button connections and everything there was. O.K.

I was wondering if there's a thermal or short reset somewhere in the power supply or if there's a jumper on the mobo for this lead, and also curious if my Antec 350W power supply is enought to handle all the "stuff" connected to it. I have two HD's, two optical drives, a ZIP drive, two fans in front, two in back, one on the two HD's, a Iceberq on the Radeon, and the fan on the CPU. Sounds like alot to me.

I was just thinking perhaps the Radeon 9800 Pro with it's power connection put it over the top or perhaps hot plugging a fan shut something down temporarily.

Any thoughts ?


P.S Benchmark time on that 9800 Pro !

02-06-04, 06:32 AM

hard to tell for sure..unless you monitor voltages...

also it's usually best to connect case fans to the PSU directly..

02-06-04, 06:41 AM
you were pluging fans in while the PC was on ? that is a no no.

try unpluging everything and let it sit for a few minutes then replug it and try to start.

you can check fans using a 9volt battery to see if they work.

02-06-04, 07:18 AM
Originally posted by westy
perhaps hot plugging a fan shut something down

:eek: :nope:

02-06-04, 08:00 AM
After I let it sit for 15 minutes, I was able to restart the computer. But, the 3 prong fan connection on the mobo still seems to be dead. I ran some tests last night after my post (3DMark, SiSandra) and everything seems to be running fine under load so perhaps my power supply isn't underpowered.

I should be able to check the power connection on the mobo with my voltmeter to I would think.

What damage could I have done my hot plugging that fan ? The only reason I use the connection on the motherboad is I'm able to monitor the fan that way.

Thanks for the insights !

02-06-04, 09:31 AM
Originally posted by westy
under load so perhaps my power supply isn't underpowered.

Nah, a quality power supply like an Antec, your 350 watts is an honest 350 watts of quality power. Way more than enough to handle your components. Don't let the battle of "who's got the highest wattage PS in their rig" influence you. People going to 450, 500, 550 watts..purely for sensationalistic bragging rights.

02-06-04, 09:40 AM
Any thoughts on that fan connection YOS ? I didn't try shutting down and connecting ther fan then restarting but I will when I get home.

Thanks !

02-06-04, 09:43 AM
Originally posted by westy
Any thoughts on that fan connection YOS ? I didn't try shutting down and connecting ther fan then restarting but I will when I get home.

Thanks !

The fact that you hot swapped it...anything is now possible. Could completely fail to work, could sporadically work, could display symptoms, power supply could even be not working 100% healthy anymore. Ripple effect from the surge caused by hot swapiing can even spread to other components such as RAM, CPU, other peripherals.

Or you could be lucky, completely reset CMOS, completely power cycle it, and it may run fine.

It would just always be a question mark in my mind from now on, that occasional lockup it might experience, or occasional failure to make it through POST on power up....all sorts of little issues may or may not arise.

02-06-04, 10:35 AM
I looked in the manual on the CMOS, and think I can handle that. If I understand this correctly, I will have to go in and reset my BIOS settings and that's all correct ? (After I clear the RTC per instructions). Nothing else software wise will change ? I'm curious, how would clearing this effect the fan connection ?

I'll try shutting down, plugging in the fan and restarting first.

I learned a valuable lesson this time. Let's hope it's not an expensive one ! :(

Thanks again !

As my daughter would say, "Oh, what a day......." It doesn't help that last night my wife was transferring pictures from the digital camera onto her computer and didn't disconnect the USB cable normally. (just pulled it out). In her words, "some wizard thing came up and I said o.k." Now she's unable to get onto our internet access thru the router. So, once I get my mobo figured out, I need to start troubleshooting her accomplishment !

02-14-04, 09:02 AM
Well, one of those little issues may have just come up. I've been trying to burn a DVD and Roxio DVD Creator locks up when it starts encoding the movie. I've tried it 3 times now and I'm having the same problem. It worked fine before, because I've burned a dozen or so DVD's.

I'm going to try re-capturing the video one more time and see if that helps, otherwise,,,,,,,,


The Dude
02-14-04, 12:11 PM
The power supply does have an overload, reset function. It's called a crowbar circuit. If you overload the supply the crowbar circuit trips and kills the supply. Kills as in shuts it down before it can be damaged. The crowbar circuit is powered by the AC mains. The only way to reset it is to remove the AC power coming in. Unplug it or shut the mains switch on the back off for a minuit or two. Now the fan connector on the motherboard is limited in the amount of current it can supply. If you put too many fans on it or accidentally short it out you blow the transistor that drives it. It's a sort of failsafe circuit, you blow the transistor instead of hosing your motherboard. Hard to say if the rpm sensor still works? You could try feeding the 12V to the fan from a 4 pin plug molex and then run the ground and speed sense wire to the 3 pin on the mobo. Ground is ground, all the black wires end up on a common ground connection in the power supply.

02-15-04, 01:08 PM
Thanks for the info ! I didn't have a glitch like I thought I did. For some reason, one of the mini-DV tapes I was processing just locked up my system. I should check with Zooner on this 'cause I know he does allot of taping.... anyway, I tried 3 or 4 times but the darn thing kept locking up so I deleted the capture video that it locked up at each time and the DVD burn worked fine. I have a ways to go on my mobo, so I think I'm going to wait to RMA it until I head up north this spring. That way I won't be out a computer for two weeks.

I did try resetting the CMOS and that had no effect on the fan connector. Still dead. I'm running the fan off one of the 4 pin Molexís right now. I wanted to run it off the mobo connector that way I could monitor the fan RPM of my OC'd video card.

I'll try shutting it down, turning it off and restarting next time I shut down. Who knows, perhaps that will reset it. I'm thinking now though it had nothing to do with hot plugging since it didn't work from the git-go because I had the Vantec VPU cooler installed and plugged in at start up and it didnít work. I checked the wires on the cooler and they mirror the connection requirements in the Asus manual, so it's anybody's guess what happened.

Thanks again folks !