I just assembled my first PC. My case is the nzxt s340 and my power supply is a xfx 550w bronze, The motherboard is an Asus H97 plus. Everything is working correctly when powered on - the fans and graphics card are working and the ram is detected in the boot screen. However, it will not switch on naturally. I must switch it on at the power supply, wait for the green light to appear on the Motherboard, and then switch it off and on quickly. This causes the PC to boot into the BIOS. If I press the power button on the case, it will then switch off and I must repeat the process again for it to switch back on. What may be at fault?
PC won't turn on by pushing the power button, but it turns on if I flick the power supply's button off then on.
- Thread starter C117
- Start date
Solution
- May 18, 2007
- 23,815
- 5,265
- 108,890
Sounds like something might be tripping a lock-out in the PSU and is forcing you to power-cycle the PSU to reset the lock.
Since you have to switch it on, then off, and on again before getting it to boot, something might be drawing excess current on the 5VSB output: you turn it on, whatever is drawing surge current from 5VSB charges up a bit, trips the over-current protection on 5VSB, then you turn it off to reset the fault, turn it on again and power-up the PC before the over-current has a chance to trip again.
Does the 5VSB LED on the motherboard turn off when the PC refuses to power up? If it does, that does indeed indicate that the 5VSB supply is shutting down for some reason.
It could also be that the PSU itself is defective and is tripping its own protections due to an internal fault.
Since you have to switch it on, then off, and on again before getting it to boot, something might be drawing excess current on the 5VSB output: you turn it on, whatever is drawing surge current from 5VSB charges up a bit, trips the over-current protection on 5VSB, then you turn it off to reset the fault, turn it on again and power-up the PC before the over-current has a chance to trip again.
Does the 5VSB LED on the motherboard turn off when the PC refuses to power up? If it does, that does indeed indicate that the 5VSB supply is shutting down for some reason.
It could also be that the PSU itself is defective and is tripping its own protections due to an internal fault.
Thanks for the response!
Once I switch on the power supply, the 5VSB LED lights up and stays lit until I switch the power supply off. Pressing the power button on the case just doesn't have any effect unless the PC is already on, then it switches it off. It only boots after quickly turning the power on and off at the power supply.
- May 18, 2007
- 23,815
- 5,265
- 108,890
The PC automatically turns on without touching the power button the second time you toggle the hard-switch? In that case, something is causing the power management chip to glitch during 5VSB power-up and that something could be bad/noisy power on the 5VSB output. If you have a multimeter, check the voltage on the purple wire (5VSB) to see if it might be out of spec - that might explain why the APM/soft power button is not working for turning on the PC.
- May 18, 2007
- 23,815
- 5,265
- 108,890
Unless XFX used non-standard color coding, there should be a purple wire going into pin #9 of the 20/24 pins ATX connector. It will be the second to last pin on the row opposite from the connector's locking pin for a 20 pins connector or fourth on the 24 pins one.
Ah, yes. I found the purple wire. I placed a digital voltage tester against the wires while it was powered on, but nothing was detected on any of the individual wires, but where they're grouped together, it reads 12 36.
There is a faint and fast chirping/ticking sound coming from somewhere within the case, but I can't pinpoint where.
- May 18, 2007
- 23,815
- 5,265
- 108,890
If the motherboard's standby/5VSB LED is lit, you should be reading 5V from the purple wire to ground/black/case.
If you are reading 12V on the 5VSB wire by backprobing the ATX connector, your PSU's 5VSB output is busted (loss of output regulation) and you need to replace your PSU before the abnormal high voltage on the 5VSB output blows something up on the motherboard. Ideally, you should quit using your PC and disconnect the PSU until you get the replacement.
Here's a story which might resemble your situation:
http://www.tomshardware.com/reviews/psu-repair,4147.html
If you are reading 12V on the 5VSB wire by backprobing the ATX connector, your PSU's 5VSB output is busted (loss of output regulation) and you need to replace your PSU before the abnormal high voltage on the 5VSB output blows something up on the motherboard. Ideally, you should quit using your PC and disconnect the PSU until you get the replacement.
Here's a story which might resemble your situation:
http://www.tomshardware.com/reviews/psu-repair,4147.html
The digital voltage tester either reads nothing, 12 or 12 36, except at the system panel connectors; there are more figures after the 36 in that case. The noise is either coming from the power supply or one of the connections to the system panel connector. I plugged these (+LED, -LED, HDD LED, and POWER SW) in as per the motherboard's instructions (Just a picture). Having looked at other people's posts complaining of similar issues, they all use ASUS motherboards, and some claim the motherboards are at fault. I have yet to update the motherboard. Could the motherboard be at fault, or is it almost certainly the PSU? The first time the PC booted, it mentioned that the board activated anti-surge protection due to a potential fault with the PSU, but has not since.
Thanks for the article, I'm reading through it now.
- May 18, 2007
- 23,815
- 5,265
- 108,890
Are you sure you are using the meter properly? If the motherboard's 5VSB LED is lit, it is impossible for the meter to read "nothing" from the ATX connector's purple wire to ground since that LED is there specifically to tell you there is power on the ATX 5VSB supply.
What is "12 36" ? Are these two separate readings? Did you omit the period or comma in the number? What do you mean by "more figures after the 36"? If you mean 36.xxV, either you are doing something wrong or something has gone horribly wrong since nothing inside the PC enclosure should be anywhere near 36V.
What is "12 36" ? Are these two separate readings? Did you omit the period or comma in the number? What do you mean by "more figures after the 36"? If you mean 36.xxV, either you are doing something wrong or something has gone horribly wrong since nothing inside the PC enclosure should be anywhere near 36V.
Sorry, I have not used either a multimeter or digital voltage tester before, but I'm not using a meter. I am using a voltage tester because I don't currently have a multimeter, so I thought I'd try the voltage tester and see if that could tell me anything. It doesn't read anything when pressed against the purple wire (The screen on the device is blank). It has a sequence of numbers that either appear or do not, starting at 12 on it its own, 12 with a 36 next to it, 12 36 55, 12 36 55 110, etc. The figures are separated by a V above and between the figures. I'm using the onsite digital voltage tester. It has a flathead screwdriver tip. For example, it reads 12 on my micro USB cable when placed anywhere across the wire, but when placed against the metal tip of the cable, it reads 12 36 55 110.
- May 18, 2007
- 23,815
- 5,265
- 108,890
Ah, just a crude voltage indicator test light of sorts for very basic electrical testing. Far too coarse for use with analog or digital circuit power supplies.
Tolerances on PC supplies are 5%, so you need a 3.5 digits multimeter to make useful measurements there. Even the $5 Shenzen Special meters at the local hobby shop should still be accurate enough for this, just don't use it for high voltage/current stuff since these cheapies are often designed with total disregard for safety and lack input protection.
Tolerances on PC supplies are 5%, so you need a 3.5 digits multimeter to make useful measurements there. Even the $5 Shenzen Special meters at the local hobby shop should still be accurate enough for this, just don't use it for high voltage/current stuff since these cheapies are often designed with total disregard for safety and lack input protection.
Oh, okay. Thank you.
I'm currently trying to post the motherboard, but I cannot find where to place the flathead screwdriver. I tried between the system power connector's PWR_SW pins, but nothing happened. I flicked the hard switch on and off, with the case's POWER_SW connector in, and it booted.
The fast ticking sound is coming from the PSU's fan, I believe.
- May 18, 2007
- 23,815
- 5,265
- 108,890
Remember a few posts ago when I recommended that you quit trying to use the PC and unplug the PSU until you replace it?
Before, you had a PC that was known still bootable. Buy or borrow a PSU, put it in, if that solves the issues then you know with reasonable certainty that the problem was the PSU. Now that the PC won't boot, it could be either that the PSU completely died (not the case if the LED still lights up) or that your repeated attempts at turning the PC on with a suspect PSU may have fried the motherboard and, if you are unlucky, other components.
This is a bit like shoving car repairs forward until all those minor issues cause a major failure.
Before, you had a PC that was known still bootable. Buy or borrow a PSU, put it in, if that solves the issues then you know with reasonable certainty that the problem was the PSU. Now that the PC won't boot, it could be either that the PSU completely died (not the case if the LED still lights up) or that your repeated attempts at turning the PC on with a suspect PSU may have fried the motherboard and, if you are unlucky, other components.
This is a bit like shoving car repairs forward until all those minor issues cause a major failure.
No, it's booting with the hard-switch flick. I removed the parts of the last post which no longer applied, but not quickly enough. Everything is functioning as it was since I asked this question. Sorry about that. I inferred that the recommendation to unplug the PSU completely was due to the readings from the digital voltage reader that were to be disregarded, though, which is why I attempted to post the motherboard. I'll leave it be completely now.
TRENDING THREADS
-
-
-
News US sanctions transform China into legacy chip production juggernaut — production jumped 40% in Q1 2024- Started by Admin
- Replies: 31
-
RTX 4070 vs RX 7900 GRE faceoff: Which mainstream graphics card is better?
- Started by Admin
- Replies: 70
-
Question I have been stuck between NVMe and SATA SSD. What should I do now?- Started by maniac2556
- Replies: 15
-
Question New pc build r9 7900x3d rtx 4080 super no post only ram rgb turns on- Started by Harvey Durward
- Replies: 5
-
Question 1TB HDD 80% Fragmented, Windows 10 Optimise Drives Program Doesn't Help
- Started by sdfbvcxbf
- Replies: 7
Facebook
Twitter
Instagram