ATX computer power failure 1

[swayda]

I've got a problem. I'm building my first ATX ff computer.
The problem is that it won't kick over. I don't think it's the power supply as it's new. At first I didn't have the fan connected to the motherboard because it was had a molex connector, but I've replaced that with a 3 pin mini and still when I turn the power on absolutely nothing happens. I mean nothing. The fan doesn't even rotate. Is there anything I'm missing or is it possible I've gotten ANOTHER bad power supply. It's not the motherboard as this is the second board I've gotten the same reults with. The 1st one was a Soyo, this one is a Tyan. Any suggestions?

 

[jgoodman00]

I am assuming you have checked the connection from the power supply to the mainboard & from the power supply to the power switch. If that is the case, & both are correctly connected then i am afraid it sounds as though your power supply is faulty. If you have a multimeter, you could check the feed to the mainboard & the power switch, because they should both be live at all times...I believe the mainboard manual will tell you what pin contains what feed, & you should then be able to work out what pin that corresponds to in the iso connector between the power supply & mainboard James Goodman
j.goodman00@btinternet.com

 

[lgebhart]

If the CPU isn't seated properly, it won't power.
If the fan isn't secured to the CPU properly it won't power.
If you have jumpers or dip switches to set for the board and they aren't right it won't power
If the fan isn't connected to the 3 pin connector on the Mobo properly it won't power
If the ATX connection isn't all the way in, it won't power
If the panel led's and power button are not on the correct pins it won't power. (these are the blue and white, green and white, etc. cables that connect to the board)
Last but not least if the power supply is no good it won't power

Make sure your Video Card is seated properly too.

I have had the same thing happen and it's amazing what little things will keep the system from powering at all.

Good luck!
ggebhart@clover.net
I hope I never get too old or arrogant to learn something new!

 

[AidanEnos]

They missed the easy answer:

AT power supply hooks to a power switch that toggels on and off, there is a thick black power cord that comes from the supply to that switch.

ATX power supply has a little jumper called ATX-sw right beside your HDD LED, reset, fan, etc. When I upgraded I use my reset switch and connect that to the ATX-sw jumper. All it does instead of toggling power on and off it sends a .5 second signal to the motherboard to power up. ATX power supplies have a power switch on the back.

AidanEnos

 

[swayda]

I thank everyone for their suggestions but I guess the real question is this. Will the fan on the power supply spin when the power supply is turned on, and this one does have an on/off switch in the back. I've built 3 other computers but they were all ATs in which case they fan would spin even if no power was running to the MB. Has anyone ever actually seen an ATX power supply where the main fan didn't spin at all that turned out to be good?

 

[AidanEnos]

no, the fan won't spin until you spark the ATX-sw jumper. To test it just find the jumper on the fron of your board and short it with a screw driver. Just a quick 1/2 second touch will signal it to power up.

Stop thinking AT and the POWER SWITCH theory... think of a virtual switch that the motherboard sends a signal to... there is NO TRADITIONAL SWITCH... stop looking for it.

Read my other post again, if you connect your reset switch to the ATX-sw jumper you're off to the races... it's your new power switch.

AidanEnos

 

[tlcscousin]

This might not sound right but I bought a new tower and it has a power switch on the back. I turned it on and low and behold nothing worked.I then looked on the front and there is another button to push.What I thought was the reset switch at first was actually another power swich and both had to be used for the first time and then after the initial time the one in the front is the only one needed for shut down and startup.

 

[swayda]

AidanEnos, I am NOT thinking AT. I've built three of them and am quite aware there are no power cords leading to the switch in the front. This ATX, I repeat ATX with the P1 power connector DOES have a switch in the back. Second, that doesn't answer my question about whether the ps fan will power up if the power supply is disconnected..

I'll certainly give your suggestion a try, but I'd truly like to KNOW whether I've got a real ps before I try, otherwise this computer may make a crater in the ground when I throw it at it.

shovel204, I'm building this machine. I'm quite aware of the switches on the unit.

Thank you all for your efforts.

Don Swayser

 

[drdak67]

Just in case you overlooked this detail...
Is your power supply powerful enough for your cpu/mb combo?
Some cases come with 250 and ever 233 watts power supplies. You might need at least 300 if not more.

Just a thought

 

[edfair]

Can't speak for all ATX PS fans, but some do run all the time (start turning as soon as the power cord is installed). I suspect but can't quote a survey, that the PS without switch should have fan running immediately and the one with a master switch will only run when the switch is on. This is confirmation for you that some do have external switches, and some don't. just in case you are feeling frustrated with some of the answers. Ed Fair
efair@atlnet.com

Any advice I give is my best judgement based on my interpretation of the facts you supply.

Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[AidanEnos]

With mine,

No the fan doesn't spin unless you have hit the power jumper, even with the power switch on the back of the ATX power supply turned on.

The power supply will NOT turn on unless you hit that jumper. That jumper IS your power switch, and believe me I know how frustrated you are. I just built my first ATX a few weeks ago.

I bought new 256MB DIMM 133 MHz, plugged it into my old mobo and only saw 128MB but it worked fine, later found out thtat my old mobo olny supported 128MB/DIMM slot.
So I bought a new mobo and T-bird 750, brought them home, got up at 7:00am Saturday ripped the old machine apart, got the new one all set up and I had an AT power supply, not an ATX - time was 7:45 am and NO stores open.
So I got the new power supply, hooked it all up and sat dumbfounded at the total lack of EVERTHING. Power switch did jack, I was just dead in the water. I posted here actually adn got no response, finally I took a guess and shorted that jumper and was in buisiness!!!

Don't feel bad, I know you are frustrated - but I'm sure that's your resolution. Make sure the power supply is on and hit that jumper and you should see life. The power supply won't activate until it has a load, minimum is mobo and 1 HDD otherwise it'll fry itself - and hit the jumper.

AidanEnos

 

[edfair]

Aidan, part of you power supply is on all the time. That portion supplies power to the turn on circuit and is also involved with power management that allows boot from things like network ping and modem ring.
And pulling cards with that power on can lead to problems. Ed Fair
efair@atlnet.com

Any advice I give is my best judgement based on my interpretation of the facts you supply.

Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[ShaithisDanoveur]

Some ATX power supplies will by default supply power and start turning the fans as soon as plugged in.

The norm however is to wait until the signal is received from the motherboard ATX power jumper. You can short this with a screwdriver and release.

Some motherboards are also configured to default to power-hot-on-AC-restore, notably Dell's. You can adjust this behavior in BIOS.

Until you have shorted that ATX power pin (and released - don't just stick a jumper on it) your power supply will likely sit there looking like a dandy boat anchor. If you have a switch on the back, this is simply useful for doing work inside the box without unplugging the AC line, nothing more. That switch needs to be on the "1" of "0/1" (sometimes looks like an I).

Then just touch your screwdriver to the ATX terminals and presto.

If you have an AT case with the power switch in front, you can substitute your reset switch for the power switch necessary to turn on/off an ATX supply. Then use the Turbo switch as your reset switch - remember you'll have to turn it off AND back on to reset the box.

Another tip - ATX power supplies won't turn on on certain mainboards without a properly seated processor. They'll start without memory in most cases, and without fans, but not without that processor inserted properly. (some will, so this isn't an absolute rule).

The main thing to remember is be patient - percussive maintenance will likely NOT solve your problems in this instance.

And remember, most of us were once where you are, building the first of what became many, many ATX's.

 

[swayda]

Thanks guys. Now I've got enough to take it through. Excuse me if I was a little slow.

 

[n9zro]

Not sure if you've resolved your problem but one thing I did not see mentioned is "Be sure that that if you are using metal "standoffs" to mount the board that none of them are touching any traces on the back of the MB, I have encountered this a couple of times and it sure will keep the system from powering on, so double check the physical mounting of your board and make sure nothing is grounded out.

Good luck

Alan R

 

[swayda]

Thanks Alan, but the board is attached with four brass mounting studs. Don Swayser