Think my PSU is dead but, would prefer a second opinion.

[BrentOnTheBass]

Hello everyone! 🙂 I am trying to start learning to work on computers, and today my grandmother gave me a HP Pavilion a6700y Desktop that she used to have that suddenly stopped working one day. The problem was out of nowhere it just stopped turning on completely.

so I took it upon myself to make this my first project, because she said if I fixed it I could keep it and its better than my computer so 😎

THE PROBLEM:

When the power button is pressed there is absolutely no response. No fans start, no lights go off, and no sounds are made. The only indication that the computer isn't broken completely is that when the power cord is attached a little green light comes on just below the power cord. (I've seen videos where people had troubles with this green light flashing but mine is solid.). I have looked up as much info as possible, including videos on all computers not booting, specifically the a6700y, reading the stickies and so on. I began by checking the power cable multiple times and it didn't work. I also have a bass amplifier cord that is the same so I tried it and nothing changed. There is no power switch so the only thing I can assume is that it is the first variable; the power supply is broken.

Now my main question is does this sound right to anyone else? I'm a little intimidated by computer hardware because I'm new to the whole aspect of opening up a computer but I feel like this may be a little simpler than other things that could have went wrong. My first guess is that maybe I should see if the fuse blew in the PSU, and if not I need to buy a new one. If I do need to buy a new one I may need some assistance with that. Sorry for the long post and little knowledge, I'm new to this.

 

[Steltek]

You are on the right tack by checking the power supply first as it is the most obvious possible cause.

First, the obligatory warning for beginners -- you are messing with electricity here and thus can seriously hurt yourself if you aren't careful. So, be safe about it - no emergency room or coroner visits tonight! 😉

The paperclip test would be a good place to start: simple, quick, and 90% of the time will let you know if the supply is totally dead or not. Hooking a case fan up to one of the power leads increases its effectiveness even more. While it isn't necessary to dismount the supply from the case, if you leave it mounted you do want to make sure all the power leads are unplugged from all components of the system and also that you don't ever touch the paperclip or otherwise let the paperclip touch the metal of the chassis anywhere during the test. Also, power supplies have capacitors which do retain current, so be careful even when the AC cord is disconnected.

Now for the test -- seeing is easier than describing:

http://www.youtube.com/watch?v=ixcWCrYpw3Y&feature=youtu.be

Please post back with the results.

 

[denis280]

You are on the right tack by checking the power supply first as it is the most obvious possible cause.

First, the obligatory warning for beginners -- you are messing with electricity here and thus can seriously hurt yourself if you aren't careful. So, be safe about it - no emergency room or coroner visits tonight! 😉

The paperclip test would be a good place to start: simple, quick, and 90% of the time will let you know if the supply is totally dead or not. Hooking a case fan up to one of the power leads increases its effectiveness even more. While it isn't necessary to dismount the supply from the case, if you leave it mounted you do want to make sure all the power leads are unplugged from all components of the system and also that you don't ever touch the paperclip or otherwise let the paperclip touch the metal of the chassis anywhere during the test. Also, power supplies have capacitors which do retain current, so be careful even when the AC cord is disconnected.

Now for the test -- seeing is easier than describing:

http://www.youtube.com/watch?v=ixcWCrYpw3Y&feature=youtu.be

Please post back with the results.

That! the third opinion:thumbsup:

 

[BrentOnTheBass]

Well I tried the paperclip test and the fan came on. (I'm not entirely sure how fast the fan is supposed to run but I could feel air coming out of it.)

I must admit I am stumped now... I was pretty sure it was going to be the power supply. Lol

 

[Steltek]

All this test means is that your power supply is turning on. It doesn't necessarily mean that it is putting out the necessary and correct voltages. It could simply have one or more bad voltage rails or it could even have some blown capacitors inside.

Next step would be to either swap the power supply for a known good one, or (if you have one) to use a multimeter to test the existing supply. As long as you are careful, you can test with the power supply connected to the motherboard to provide the necessary load (test the wires at the top of the connector after turning on the power switches). Or, you can hook a fan up to it and use the paperclip to activate it like you did the first time.

http://pcsupport.about.com/od/toolsofthetrade/ht/power-supply-test-multimeter.htm

ATX power supply voltage pinouts are as follows:
http://pcsupport.about.com/od/insidethepc/a/atx-pinout-24-pin-12v-psu.htm

To see it done:
http://www.youtube.com/watch?v=ac7YMUcMjbw

If you don't feel comfortable doing this, you can pick up a replacement power supply and swap it out. Just make sure the replacement is physically the same size as the old one and that it is 300 watts or more (which is what the old one was).

You can also try removing the memory modules and video card (if there is one), they try to power the system to see if it gives you any POST error code beeps.

 

[BrentOnTheBass]

All this test means is that your power supply is turning on. It doesn't necessarily mean that it is putting out the necessary and correct voltages. It could simply have one or more bad voltage rails or it could even have some blown capacitors inside.

Next step would be to either swap the power supply for a known good one, or (if you have one) to use a multimeter to test the existing supply. As long as you are careful, you can test with the power supply connected to the motherboard to provide the necessary load (test the wires at the top of the connector after turning on the power switches). Or, you can hook a fan up to it and use the paperclip to activate it like you did the first time.

http://pcsupport.about.com/od/toolsofthetrade/ht/power-supply-test-multimeter.htm

ATX power supply voltage pinouts are as follows:
http://pcsupport.about.com/od/insidethepc/a/atx-pinout-24-pin-12v-psu.htm

To see it done:
http://www.youtube.com/watch?v=ac7YMUcMjbw

If you don't feel comfortable doing this, you can pick up a replacement power supply and swap it out. Just make sure the replacement is physically the same size as the old one and that it is 300 watts or more (which is what the old one was).

You can also try removing the memory modules and video card (if there is one), they try to power the system to see if it gives you any POST error code beeps.

I'll try to do this later today, I'm unfortunately going to be busy most of the day. When I do get around to it I will keep you posted. Thank you though! 🙂

(I did however try to take a PSU off of an old computer I had and sadly though it was the same size it didn't have the right connectors on it.)

 

[BrentOnTheBass]

Ok so I tried to do the multimeter thing. And this is my thoughts afterward. I may sound really dumb but I tried to include pictures to make up for my lack of knowledge.

Though it isn't really important, here is what I'm working with ^

Next is what I did, the red arrow is showing the connectors that I tested (sorry I don't know the different names for the connectors) these actually were very close to the expected voltage. Close enough to be in working shape I would assume. Though I haven't been able to test it with a fan or anything. The Blue arrow is pointing to the black connectors, what actually connects to my computer. I assumed since both the connectors are connected to the same wires, testing the white connectors was fine. (Seeing as how I can't stick the multimeter in the black one. Lol)

This last part is my PSU's 24pin connector. I don't know what the difference is but unlike the video I'm not able to test the volts in it because the multimeter doesn't fit in it... I'm a bit stumped again because since all the connectors I showed in the previous picture were fine I guess it would all come down to this part but I can't check it but I did notice this and was wondering if this was normal?

Is this supposed to be empty? There is no extra wire laying around so if this is wrong than this wire has magically disintegrated because until I did, this computer hadn't been opened up before.

I have another PSU from another computer but sadly it didn't have the black connectors to attach to my computer. It was the same size and voltage though.

Besides all this, all I can think of now is maybe the computers power button is slightly dislodged or something and is just not activating the PSU. 😕

 

[Harvey]

Well I tried the paperclip test and the fan came on. (I'm not entirely sure how fast the fan is supposed to run but I could feel air coming out of it.)

I must admit I am stumped now... I was pretty sure it was going to be the power supply. Lol

The start switch switchs a momentary switch that grounds a logic pin on the startup circuitry while it is pushed. The paperclip test is a way to duplicate this condition. The fact that the fan spins up when you do it suggests that either the switch, the wire pair or the plug that connects the wires to the motherboard is faulty.

To test this with an ohm meter, stick a fine piece of solid wire or a pin or sewing needle into each terminal, and measure the resistance across them. It should measure 0 ohms when you push the switch and "open" or infinite when you release it.

If visual inspection shows that the problem is the plug to the motherboard, the contacts can sometimes be repaired, or you could simply cut the wire and replace it by splicing a similar 2 pin plug and its wires from some other broken piece of gear.

If it's the switch, you may be able to remove it from the case and replace it if you can find a replacement with the same form factor that can use the same button cap. You want an SPST (Single Pole Single Throw) momentary switch. If you find a double pole switch, you can use one side or connect both poles in parallel for redundant contacts.

As Steltek said, even if the fan spins, there's still a chance that the PSU is faulty in another way.

Next is what I did, the red arrow is showing the connectors that I tested (sorry I don't know the different names for the connectors) these actually were very close to the expected voltage. Close enough to be in working shape I would assume. Though I haven't been able to test it with a fan or anything. The Blue arrow is pointing to the black connectors, what actually connects to my computer. I assumed since both the connectors are connected to the same wires, testing the white connectors was fine. (Seeing as how I can't stick the multimeter in the black one. Lol)

Here's the connection diagram for the 4 pin Molex connector (and 3 pin fan connector):

This last part is my PSU's 24pin connector. I don't know what the difference is but unlike the video I'm not able to test the volts in it because the multimeter doesn't fit in it... I'm a bit stumped again because since all the connectors I showed in the previous picture were fine I guess it would all come down to this part but I can't check it but I did notice this and was wondering if this was normal?

Is this supposed to be empty? There is no extra wire laying around so if this is wrong than this wire has magically disintegrated because until I did, this computer hadn't been opened up before.

I have another PSU from another computer but sadly it didn't have the black connectors to attach to my computer. It was the same size and voltage though.

Besides all this, all I can think of now is maybe the computers power button is slightly dislodged or something and is just not activating the PSU. 😕

A 24 pin ATX power connector has the same pinout as a 20 pin connector with four extra pins to be able to provide more current capacity at ground and specific voltages. Some manufacturers provide separate 20 and 4 pin connectors that fit next to each other in the 24 pin socket. Others provide 24 pin connectors that are clearly intended to be broken apart when used with 20 pin motherboards.

Here's the connection diagram for the 20/24 pin ATX connector:

Starting at the lower right, the first two pins on the 4 pin part are COM (ground) and +5V. After the break, they continue with two more +5V and N/C, which means No Contact. Your red arrow is pointed at that pin so this is not an issue.

The CPU fan spun up when you tried the paperclip test so if you're still having problems, you're on the right track to try another known good PSU. If you're careful, you don't have to remove the current PSU to do it. Just open the side of the case, lay the case down on its side with the motherboard up (and plenty of workspace around the machine), and carefully connect power wires to the motherboard and the hard drive. You just want to see if it beeps and you start to get a normal video display. If not, you can quickly power it down and assume that your PSU has problems. If it looks like it's starting to boot normally, you can confirm that it's working by trying to do a full boot up.

Hope that helps. 🙂

 

[Ketchup]

Hello BrentOnTheBass, hope you were ready for the PSU lessons from Harvey and Steltek. Good stuff.

Another thing to consider is a component that is shorting the connection. One way to test this would be to plug in only the 24-pin and 4-pin connectors to the motherboard. If it boots up this way, there is probably a short somewhere (either in a wire or one of the powered components). If it doesn't, it is probably the switch or an almost-dead unit. I have seen several power supplies that show that green light as bright as new, but are as dead as a doornail.

Good luck!

 

[Steltek]

FYI that empty pin on your 24 pin power supply connector is where the -5v pin would have been on an older ATX power supply. The more modern ATX power supplies have eliminated the -5v pin, so you end up with an empty pin where it used to be to allow continued compatibility with the existing standard 20/24 pin power supply sockets on ATX motherboards.

To short the connection like ketchup79 was suggesting, plug the motherboard and CPU power connectors back in to the motherboard, hook up the power cord, and turn the power supply on. Trace the power switch leads from the switch at the case to where they plug in to the motherboard. Unplug those switch leads from the motherboard switch headers (making a note of how to replace them later), then use a flat screwdriver to momentarily jump across those two pins where the power switch was plugged in. If it starts up, you know you definitely have a bad case switch. If it still doesn't do anything, you will have to backtrack and do some more testing on the power supply as it could still be either the power supply or motherboard which is bad.

 

[BrentOnTheBass]

All of you are so remarkably helpful!

I'm going to do what you guys said and try turning it on with only certain connectors plugged in and after that try using the multimeter again now that I understand what I'm doing a little more.

I'm going to try to get my hands on a new power supply, I'm pretty sure its the problem since the computer is getting no power and not even displaying error messages or anything.

I can't thank you guys enough for all the help! 🙂

 

[Harvey]

Oops! Just noticed that no one (including me) reminded you to unplug and reseat your RAM, vid card (if not onboard video). If the problem persists, try one stick of RAM, then the other.

 

[Steltek]

Oops! Just noticed that no one (including me) reminded you to unplug and reseat your RAM, vid card (if not onboard video). If the problem persists, try one stick of RAM, then the other.

Plus, if this doesn't work, try to remove all the memory modules and power the system to see if it will give you any beep codes (which would be an indication the motherboard is trying to POST).