PSU does nothing but light up the standby light


I have been working on a pc build and it hasn't gone exactly to plan. I initially tried to install an Antec 550W PSU, but when I installed it, the system would not POST. The case and heat sink fan both turn on, but thats as far as it goes.

I purchased a Thermaltake 850W power supply, hoping to fix the issue, but this PSU will do nothing but power on the motherboard standby light, no fans or anything.

I have 2 separate motherboard/processor combinations I've been working with, which I'll list below, with exactly the same results on both. I took the rosewill 850W out, and it WILL power on the fans and HSF on a 3rd, much older computer.

My question is, why would the rosewill do NOTHING on 2 separate mobo/processor combinations and work on a 3rd? (bad motherboards?) and why would the Antec at least power the fans on the same 2 combinations?

I think I have more issues that just the PSU, but im starting from the ground up :)

4 answers Last reply
More about light standby light
  1. You have more than a PSU issue for sure. Try an external build to test core components. Place motherbord on non-conductive surface,like box, hook up PSU, plug in your RAM,video card with the CPU and cooler all installed on the board. Hook to monitor. Next, touch a screwdriver to the 2 power switch prongs on the motherboard where your case power switch plugs in. You should see the motherboard Splash screen come up for a second,if not ,one of your core components is defective.You will get an error message cause you have no drive installed but that is ok,turn off the same way you turned it on.Hope this narrows it down for you.
  2. Full system specs?

    If you do not have much experience, look at this:
    You may find something that you overlooked.

    Work systematically through our standard checklist and troubleshooting thread:
    I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

    If not, continue.
    The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

    I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

    Breadboard - that will help isolate any kind of case problem you might have.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. At this point, if you do not have a system (internal case) speaker, you really need one.

    Make sure you plug the CPU power cable in. The system will not boot without it.

    I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

    If no beeps, LED's, or fan activity:

    Check for line power at the PSU input. Extension cords, power strips, and power cords do fail.

    If you have power and no beeps, suspect components in likely order are PSU, motherboard, and CPU.

    Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

    At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

    If the system beeps:
    If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

    Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

    Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
    At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

    Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
  3. Did you plug the CPU power connector in? That sounds like something that is easily overlooked and can cause the same results you are describing. In case you don't know what it is, look for a 4 or 8-pin jack on the motherboard, near the CPU. Power supplies tend to have a plug that fits either when you put them together, unless it is a power supply made specifically for AMD or Intel processors.
  4. I know this is stupid and I have been the victim of it myself, but did you forget to press the power button? For some reason I always end up thinking that powering the PSU will turn on the computer totally forgetting that there is a power on button on the front of that case that needs to be turned on to power the computer. Cheers.
Ask a new question

Read More

Power Supplies Light Motherboards Components