This is the first computer i've tried to build and I think i have everything hooked up correctly. I have an Asus A7N8X-X mobo, 400w power supply and i get no power when i try to turn the computer on. When i plug it in i get the initial spin of the fan from the power supply but i get no more. Can anybody help me with this?
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations IamaSherpa on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
PC gets no power 1
- Thread starter frazzuh
- Start date
-
1
- #2
ski
Technical User
- Oct 11, 2000
- 2,467
If nothing runs other than the momentary spinning of the PS fan(no other fans, lights, etc.), then reset CMOS.
You will have to check your MB's manual on how to do this.
If that's ok, then make sure that the voltage selector switch on the PS is positioned for the correct voltage in your house(115 or 230V).
If ok, then make sure that the CPU's fan is securely and properly connected to the correct MB terminal.
If ok, then make sure that the main PS connector at the MB is firmly inserted. Sometimes it needs a healthy push to properly seat.
If ok, then remove the main PS connector, and check for anything abnormal with either that connector's contacts or with the contacts on the MB's connector.
If ok, then start the system with the PS connected to the MB, and install a small jumper wire on the PS's main connector between its green wire and any black wire(The jumper wire can be installed on the back of the PS's connector).
If the PS fan does not run, then the PS is bad. Replace it.
If the PS fan runs, then check the PS voltages with a voltmeter(do this with the system on and the PS connected to the MB):
Yellow and black wire - +12V
Red and black - +5V
Orange and black - +3.3V
If any of the readings are way higher or lower than the above, then the PS is bad. Replace it.
If the voltage readings are ok, then do a barebones setup with only the PS, MB, CPU, power button, and system speaker connected.
If you do not hear any beeps, then either the CPU or MB is bad. Swap them out to find the culprit.
You will have to check your MB's manual on how to do this.
If that's ok, then make sure that the voltage selector switch on the PS is positioned for the correct voltage in your house(115 or 230V).
If ok, then make sure that the CPU's fan is securely and properly connected to the correct MB terminal.
If ok, then make sure that the main PS connector at the MB is firmly inserted. Sometimes it needs a healthy push to properly seat.
If ok, then remove the main PS connector, and check for anything abnormal with either that connector's contacts or with the contacts on the MB's connector.
If ok, then start the system with the PS connected to the MB, and install a small jumper wire on the PS's main connector between its green wire and any black wire(The jumper wire can be installed on the back of the PS's connector).
If the PS fan does not run, then the PS is bad. Replace it.
If the PS fan runs, then check the PS voltages with a voltmeter(do this with the system on and the PS connected to the MB):
Yellow and black wire - +12V
Red and black - +5V
Orange and black - +3.3V
If any of the readings are way higher or lower than the above, then the PS is bad. Replace it.
If the voltage readings are ok, then do a barebones setup with only the PS, MB, CPU, power button, and system speaker connected.
If you do not hear any beeps, then either the CPU or MB is bad. Swap them out to find the culprit.
How long does this initial spin last for? 2-3 secs?
Have you connected the CPU fan to the system fan header by mistake? the motherboard needs to sense an RPM reading on the CPU fan header terminals otherwise it turns off.
Is the heatsink fitted the correct way around, this motherboard has on die temp sensing, if the heatsink is fitted the wrong way, it won't sit on the CPU die squarely so will overheat in seconds, thermal protection will take over and turn off the system.
Bad PSU?
Short? like a bad CDrom, unplug to bare minumum.
Martin
Replying helps further our knowledge, without comment leaves us wondering.
Have you connected the CPU fan to the system fan header by mistake? the motherboard needs to sense an RPM reading on the CPU fan header terminals otherwise it turns off.
Is the heatsink fitted the correct way around, this motherboard has on die temp sensing, if the heatsink is fitted the wrong way, it won't sit on the CPU die squarely so will overheat in seconds, thermal protection will take over and turn off the system.
Bad PSU?
Short? like a bad CDrom, unplug to bare minumum.
Martin
Replying helps further our knowledge, without comment leaves us wondering.
- Thread starter
- #4
franklin97355
Technical User
Try shorting the two pins on the motherboard where the power switch attach (momentarily) You may have a bad power switch. Make sure you check the manual to find the right ones.
- Thread starter
- #7
I'm having the same issue. I think its the power supply. I purchased a cheap 300w generic - shame on me. I've stripped down my system to mb, case fan and cpu. When I power on I get the green light on the mb and the fan on the heatsink, the case fan and the ps fan turn for about 1 second, then nothing. I've tried all the other fixes and haven't gotten past this point. Anything else I should look into?
thanks, selch
thanks, selch
i haven't looked @ this board layout, but some require that you connect a four-prong power cable to the board...but i do know thermal protection is onbaord and that would be the first thing to try...also make sure that the dip switches(if they are there) are set sorrectly..i spent 5 days trying to get one pc going only to fing out that the "auto" sensing cpu fsb dip was not enough
the only right answer to "why?" is: "why not?"
the only right answer to "why?" is: "why not?"
ski
Technical User
- Oct 11, 2000
- 2,467
selch,
It could be caused by either the MB, CPU, or PS.
If you have a voltmeter, then check the PS voltages as described in my 1st post in this string.
If you do not have a voltmeter, then use a different PS if possible.
If the voltages are ok or if the problem persists with a different PS, then you have to swap out the MB and CPU to find which one is the culprit.
Also, place the MB on a piece of cardboard to rule out an electrical shorting problem.
It could be caused by either the MB, CPU, or PS.
If you have a voltmeter, then check the PS voltages as described in my 1st post in this string.
If you do not have a voltmeter, then use a different PS if possible.
If the voltages are ok or if the problem persists with a different PS, then you have to swap out the MB and CPU to find which one is the culprit.
Also, place the MB on a piece of cardboard to rule out an electrical shorting problem.
I have done all the above and mine still will not work either. See my posting on My computer will not start. I have tried replacing the ps and everything in the mb. I got a new mother board yesterday of the same exact type and plugged in averything as it was when it did run. The only conclusion I can think of now is the power switch. ou might try jumping off the switch with a car key or something which is what i am going to do today later. Can that go out and shut the pc down after it is running though? Don't know but might be it.
TattooedBones
MIS
Ski - Thanks much! Having the same problem and I tried your green wire to black jumper and the machine boots like a champ. Here's my question... is it OK to leave the wire in there? The power switch seems to work OK, because I can shut down the HDDs and CD drives (but the fans all stay on with the jump wire in place). Any ideas? I don't have a voltmeter so I can't check further into the power supply but it is a very generic 450 watt. I'll see if I can borrow one from work perhaps. Anyway, thanks again, at least the machine is working for now.
TattooedBones
TattooedBones
ski
Technical User
- Oct 11, 2000
- 2,467
You're welcome, TattooedBones.
If the system does not boot with a green-to-black jumper wire not connected on the PS, then the PS is probably bad.
You can confirm this if you can get your hands on a different PS.
In the interim, a few fans running with the system turned off will not hurt anything, other than using up a little bit of electricity.
If the system does not boot with a green-to-black jumper wire not connected on the PS, then the PS is probably bad.
You can confirm this if you can get your hands on a different PS.
In the interim, a few fans running with the system turned off will not hurt anything, other than using up a little bit of electricity.
TattooedBones
MIS
Ok, I ordered an Antec True550 - that should do the trick. Also borrowed a multimeter from work. Since I've never really used one before, I asked and popular opinion around here is to set it at 20DC. I'll probe that stuff tonight. Luckily my old PS has a rocker switch on the back so I can leave the wire in for now until the new PS arrives. Thanks so much once again!
Not sure if anyone else will find this useful, but I found a URL that lets you select components and calculates your recommended PS Wattage.
I have no affiliation with that website or anything, just thought it might be a usefull addition to this thread. My min. supply is 433 and I'm using a very cheap 450 Watt. Thanks to all & especially Ski for the info.
-TB
Not sure if anyone else will find this useful, but I found a URL that lets you select components and calculates your recommended PS Wattage.
I have no affiliation with that website or anything, just thought it might be a usefull addition to this thread. My min. supply is 433 and I'm using a very cheap 450 Watt. Thanks to all & especially Ski for the info.
-TB
- Status
Similar threads
- Locked
- Question
- Locked
- Question