Strange Motherboard/Power issue

steheap · Post by **steheap** » September 25th, 2005, 8:49 pm

I have a Gigabyte GA-7VRXP and had an issue with the computer restarting after the Windows desktop appears. I thought it was a power supply issue as that smelt a bit! I changed the powersupply for an Antec 500W version, and now nothing will start. When I strip the computer to bare CPU, memory and video card, there is a small flutter of the CPU fan when I press the on switch, but then nothing more. If I measure the voltage on some of the connectors, there is no voltage present from the PSU. Something is causing the power supply to try to start, and then to instantly turn itself off - sounds like a short circuit maybe, but I am not sure how that occured when the old one managed to power the CPU up. Any ideas on what I can test to find out the root cause? Steve

richh0323 · Post by **richh0323** » September 26th, 2005, 6:04 am

Did you try the old one to see if it still works? You may have a bad new power supply. Re check all the connections once more. If you have a meter go to page 22 in the PDF link I included, check the 5volt power to ground. This is the standby power, and is what you need to go thru the power switch to turn on the computer. It is the only power you will be able to measure intill you turn on the computer. http://america.giga-byte.com/MotherBoar ... e_1101.pdf You can also turn the power supply on by jumping from PS on to ground

Large Burgershie · September 26th, 2005, 8:19 am

your comps proberly too hot. try disconnecting your comps power supply and try everything again

richh0323 · Post by **richh0323** » September 26th, 2005, 9:22 am

Another thought here, if you can test the power supply, and it won't power up connected, but will with the jumper. Remove all connectors to hard drives, fans, CD/DVD drives and just try the main board. IF that works and you power up reconnect devices one at a time, if not remove the memory and any cards connected, try again as above.

steheap · Post by **steheap** » September 26th, 2005, 1:10 pm

Great set of ideas. A couple of extra bits of information from tests I did after the first posts: 1. I can measure the correct voltages from the PSU when I link together the switch connection to ground - ie I see 5V, 12V, 3.3V. There is no -12V on the ATX connector - maybe that is no longer required on modern motherboards? 2. I have only checked for the 5V and 12V on the auxiliary connections once the main connector is on the motherboard - no sign of any voltage there. 3. When I measure voltages during turn-on, I see a short flick in the power - say up to 2.5V on my analog meter - and then off again. I suspect that I have a short somewhere - wouldnt that cause the power supply to kill all the voltages as soon as it is recognized? I will check the ideas provided so far - keep them coming! Steve

richh0323 · Post by **richh0323** » September 27th, 2005, 12:00 am

The power supply will shut down on overload conditions to protect itself.

2. I have only checked for the 5V and 12V on the auxiliary connections once the main connector is on the motherboard - no sign of any voltage there.

Are you saying that the power will be measurable at the connector with the jumper in place, but when connected to the M/B you no longer see it? If this is so have you dissconnected everything you possibly can from the M/B and tested the M/B itself? You can also do the opsite and connect up drives and not the M/B useing the jumper see if you get a power up. I know it alot of checking but it can rule out a bad M/B or not

richh0323 · Post by **richh0323** » September 27th, 2005, 12:01 am

The power supply will shut down on overload conditions to protect itself.

2. I have only checked for the 5V and 12V on the auxiliary connections once the main connector is on the motherboard - no sign of any voltage there.

Are you saying that the power will be measurable at the connector with the jumper in place, but when connected to the M/B you no longer see it? If this is so have you dissconnected everything you possibly can from the M/B and tested the M/B itself? You can also do the oppsite and connect up drives and not the M/B useing the jumper see if you get a power up. I know it alot of checking but it can rule out a bad M/B or not

richh0323 · Post by **richh0323** » September 27th, 2005, 12:02 am

The power supply will shut down on overload conditions to protect itself.

2. I have only checked for the 5V and 12V on the auxiliary connections once the main connector is on the motherboard - no sign of any voltage there.

Are you saying that the power will be measurable at the connector with the jumper in place, but when connected to the M/B you no longer see it? If this is so have you dissconnected everything you possibly can from the M/B and tested the M/B itself? You can also do the oppitsite and connect up drives and not the M/B useing the jumper see if you get a power up. I know it alot of checking but it can rule out a bad M/B or not

Large Burgershie · September 27th, 2005, 1:56 am

yowch tripple post (lolz button happy) no offence that is. ...someone prune plz ahem sorry so yes thats all i can suggest for power.

steheap · Post by **steheap** » September 27th, 2005, 6:01 pm

Yes - the triple reply is correct! I see no voltage on any of the aux connections when I plug the PSU to the mobo. I see the same when I use the old power supply, even though at the start of the exercise the old PSU was at least powering up the system to the Windows desktop. After 6 hours on this, I think I have reached the end of the road - new motherboard is next! Steve

richh0323 · Post by **richh0323** » September 27th, 2005, 11:24 pm

Yes sorry on the posts (3) not sure why that happened

Sorry to hear you didn't have any luck with the power issue, butr as long as you have everything dissconnected you can from the power supply, and off the M/B I would also assume it to M/B related