Does this PSU need replacing?

Hey all, having issues with a computer that won't POST, and I've starting troubleshooting with the power supply. The multimeter numbers look strange to me and I was hoping someone could give me a definitive answer regarding the health of the PSU. Unfortunately, I don't have access to another PSU or I would have tried swapping.

Here's my current rig:

OCZ GameXStream OCZ700GXSSLI 700W (Refurbished)
AMD Phenom II X4 955 Black Edition Deneb 3.2GHz
EVGA 896-P3-1260-AR GeForce GTX 260 896MB
G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600
Western Digital Caviar SE16 WD7500AAKS 750GB 7200 RPM
Western Digital Caviar Black WD6401AALS 640GB 7200 RPM
LITE-ON 20X DVD±R DVD Burner Model LH-20A1L-05

When I pulled the PSU, shorted it, and tested all of the voltages were within tolerance, except the 3.3V (orange) which was slightly higher (3.54).

With PSU installed and switched on but PC not powered up:

Purple: 5.15
Green: 4.41
Red: 0
Gray: 0
Orange: 0.12
Blue: 0
Yellow: 0

PSU under load (2 hard drives, CPU and DVD drive; no memory or GFX card):

Purple: 5.12
Green: .05
Red: 5.08
Gray: 5.09
Orange: 3.36
Blue: -12.54
Yellow: 12.45

What do you think? Doesn't look good?

Thanks all.

13 answers Last reply
More about does replacing
  1. Little high on the yellow ( 12v ), but still in spec
  2. I was thinking the same thing. Never try testing a PSU with no load on it, its not designed for that. All your rails look to be in spec, with the 12V rail a bit on the high side. Not only is that not a problem, but it will probably fall back in spec once the GPU is installed. I noticed you didn't list your mobo and you're trying to use one of the newer CPUs. Any chance its not supported at all or you need a newer bios then the one you have?
  3. Ah, I'm sorry. What a bonehead move. I felt like I was forgetting something in my initial post.

    The mobo is an ASUS M4A785TD-V EVO AM3 AMD 785G. BIOS Revision is 1.01G, which is supposed to support this CPU.


  4. Which 955 do you have? On Asus's CPU support list for your mobo it lists 5 different 955s. Some are obviously different in that its a 95W CPU and not the normal 125W, but there are others that seem to have no difference. You'll need to figure out which motherboard and CPU you have, and then make sure you have the correct board and bios. (some of the 955 will need a board/PCB revision to work.) Here is the link.
  5. All of your voltages look good. Well, the 3.3 volt output is under no load.

    The violet wire is the output of the 5 volt standby power supply. It will always be there if the PSU is plugged into the wall and turned on.

    The green wire is a control input to the PSU. It will be a Logic HIGH. Momentarily grounding it through the case power switch turns on the PSU.

    The gray wire is a control output from the PSU to the motherboard. This goes to a Logic HIGH when the 3, 5, and 12 volt outputs stabilize. You need this to boot.

    While I am not a fan of OCZ PSU's, the voltage readings look OK.

    Work 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.
    Looks like you have done this.

    If not, continue.

    I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different.

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

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:
    Or Microcenter or Frye's.

    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.

    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:
    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.

    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 or long single beeps indicate a problem with the memory.

    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.

    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.
  6. 4745454b said:
    Which 955 do you have? On Asus's CPU support list for your mobo it lists 5 different 955s. Some are obviously different in that its a 95W CPU and not the normal 125W, but there are others that seem to have no difference. You'll need to figure out which motherboard and CPU you have, and then make sure you have the correct board and bios. (some of the 955 will need a board/PCB revision to work.) Here is the link.

    Thanks for the link. I'm not sure there is a way to ascertain which bios is on my board without it being able to POST. I'll have to contact Asus and get the information from them. I'll post back when I figure it out.

    Thanks to you as well jsc. I have breadboarded with just the mobo, psu, cpu, hsf, and speaker. Still no POST. I'll reply back when I get the information 4745454b has requested.

  7. I was going to suggest what JSC wrote as an extra standoff in the wrong place will short the board out. If its not that, and you said you tried, then I suggest you keep looking at a possible mobo/CPU compatibility issue.
  8. I heard back from Asus. My board has BIOS revision 2103 and PCB 1.01G. My Phenom 955 is HDZ955FBK4DGI. There shouldn't be any compatibility issues as far as I can tell. I wish I had access to a spare AM3 processor to throw in there just to see if it works.

    I breadboarded the system, so there isn't any chance of a misplaced/extra standoff causing the issue.

  9. Does it beep when you try booting with no ram? Try the PSU in a different computer and/or a different PSU in that one.
  10. No beeps with no RAM. I haven't gotten a beep out of this board yet.

    I'll have access to a brand new Corsair 650TX tomorrow. We'll see what happens then.

    Thanks for the response 4745454b.

  11. If it doesn't beep with no ram its probably a dead mobo.
  12. Sounds like a possibility. It's too bad as it's brand new.

  13. Finally able to POST with the new 650TX. Now, there's another issue. The motherboard constantly restarts when the graphics card (GTX 260) is installed. It will POST, restart, POST restart...

    If I remove the GTX 260 and just use the on-board graphics, everything seems fine. What could be causing this?

Ask a new question

Read More

Power Supplies Components