Fuse in main plug keeps blowing!!!

KP84 · December 2005

Ive just built my 1st computer.
Amd 4400+
2gb Ram
2x250gb
Nvidia 7800gt
Asus a8n premium
TAGAN 480w U22

Ive wired everything up right but when i try to turn the pc on the plug socket fuse just goes out. Its got a 13a fuse and the pc just wont turn on, any idea what could be causing this????

profdlp · December 2005

Remove the PSU from the case and see if you get the same blown fuse by plugging in nothing except the main voltage cord to the PSU.

Take everything out of the case and assemble a barebones configuration on a non-conductive surface. By barebones, I mean MB, memory, CPU (with heat sink and fan!), and video card. If that works add in your hard drives and cdrom.

If all that works, carefully inspect every last inch of wiring in your computer and make sure nothing got pinched during the assembly process and pierced the insulation around the wires. You should also make sure that all of the motherboard standoffs are in the proper location and that there are no "extra" ones anywhere.

Then try it back inside the case again.

KP84 · December 2005

Well the thing is i cant remove the psu from the case unless i remove the motherboard and i will have to take everything back out becuase of my case design, but i can try it out tomorrow, any other reasons why this may be happening? Also if i just connect the psu by its self it wont actually turn on will it without a mobo and the switch that goes to the front of pc?

profdlp · December 2005

By "plug socket fuse" I'm assuming you mean the fuse supplying the wall socket. Is that correct?

It sounds like you have a dead short somewhere. Every time you retry under the current configuration you are playing russian roulette with all your computer parts. Unless you are absolutely sure your MB standoffs are in the right place and can spot a pinched wire, complete disassembly is the safest way to go.

The only thing else I'd add to my previous advice is to check the 120V/240V switch on the PSU and make sure it is set properly for the voltage where you live.

Good luck.

KP84 · December 2005

there isnt a voltage switch which is a good thing as i no what happens if thats in the wrong place

Well somone told me the only thing causing this is the earth wire from the psu, which is under the mobo so im gona have to take the whole thing appart anyway

**The fuse that blows out is the main fuse in the plug that you put in the wall socket

If i just do a barebone setup how will i actually turn the thing on?

profdlp · December 2005

KP84 wrote:

...If i just do a barebone setup how will i actually turn the thing on?

Use the tip of a screwdriver to short the two pins on the MB where you would normally attach the "Power Switch" connector from the case. That's all the switch does, anyway.

Make sure you get the right two pins!

KP84 · December 2005

Thanks a lot for the help, id still be blowing more fuses! lol

profdlp · December 2005

KP84 wrote:

Thanks a lot for the help, id still be blowing more fuses! lol

Thank your lucky stars for those fuses. You have an awesome rig there - they likely saved you from some major damage.

Donut · December 2005

After you finish with Prof's suggestions, how many things are on the same circuit? ie, microwave, coffee pot, tv.

Looking at the specs for your psu it looks like it pulls abt 10 amps on its own, (if I'm looking at this wrong somebody PLEASE corect me)

bothered · December 2005

KP84 wrote:

Well somone told me the only thing causing this is the earth wire from the psu, which is under the mobo so im gona have to take the whole thing appart anyway

Not true. If it blows straight away there is a short circuit between live and earth OR live and neutral. I wouldn't have thought a short after the PSU would blow the fuse in the plug top, if it does the PSU is either faulty or very badly designed. It could be anywhere from the plug to the PSU, even in the cable or plug itself but usually if it blows a 13A fuse that quickly there is usually a flahs or bang visible. I'd start by checking the wireing to the PC before taking it apart.

edcentric · December 2005

Pull all of the wires from the PSU to the computer. Diconect every thing and have all of the wire laying out in the open.
Now plug it in with the PSU turned off, and then turn it on.
If a fuse blows it is a fault on the primary side of the PSU. Get it replaced.

If now fuse blows, turn it off and unplug it and pull the mobo to double check the stand offs under it. If they are all right, start reconnecting things out side of the case.

You have to be methodical.

KP84 · December 2005

I did all that and it worked. So i connected it all to the case and now the fuse keeps blowing!!!

So i turned the mains off replaced the fuse and when i went to put the plug into the main socket there was a spark from the live wire and the fuse just blows!!!!!!!!!!!!!!!!!!

profdlp · December 2005

KP84 wrote:

I did all that and it worked. So i connected it all to the case and now the fuse keeps blowing!!! So i turned the mains off replaced the fuse and when i went to put the plug into the main socket there was a spark from the live wire and the fuse just blows!!!!!!!!!!!!!!!!!!

1) Describe in detail exactly what "I did all that" involved and in what order you did things.

2) There are lots of "live wires" in a computer; again, be as precise as possible.

I'm not jumping on you - we all just want to help. We're handicapped by not being there in person to see what is taking place and must rely solely on the information you give us. Don't worry about writing too much.

KP84 · December 2005

OK, Well firstly i took everything apart as it was the only to take the psu out. So i tried the psu by itself and it blew a the fuse in the plug which you put in the wall. So on my psu there is a "combined" and a "Split" switch (which splited the 2 12v) so i put a new fuse in and tried the psu alone with the switch on "split" and the fuse worked and didnt blow. After this i put the mobo on the floor (it already had the cpu, ram plugged in) and this worked (i used a screwdriver to turn the mobo on) then i switched the plug off. Then i decided to connect the whole system back up in the case. i did this and and plugged the power wire in the back of the cpu. The mains switch was off and i put it plug in the mains it it sparked and burnt a bit of the live pin along with its fuse. So i tried again, this time i put the plug in the mains first (with a new fuse, with the switch off) and when i went to plug the other end of the wire in the psu i heard another spark, i tested the plug with the normal pc and it didnt work, so the fuse blew again, i replaced the fuse and thried the power wire on a different pc and there was no spark and that pc works fine. So why am i getting sparks on this new pc

, do you thing the whole system is gone now

, or just the psu, or is a wire connected wrong.
PSU:TAGAN 480W U22
CPU: AMD x2 4400+
GPU: 7800 GT Extreme
RAM: 2gb Overclocked
Case: Thermaltake Soprano

Just ask me if any more detials are needed i despratly need help

profdlp · December 2005

I need to run some errands and won't be available for a couple of hours, but I'll see what I can do when I get back.

In the meantime, there are a ton of knowledgeable people here who might be able to lend a hand, some of whom have already posted in this thread.

Anyone wishing to help needing a good source of info may wish to check this out. (I see that Donut found it before I did.

)

We've all had problems at times getting new stuff to come together and work as it is supposed to. Hang in there, your problem does have a solution.

Straight_Man · December 2005

From the whole thread, I think the PSU is bad. The cord worked on another PC, so is not a bad cord. The system booted out of case-- case switch itself COULD be shorted, but PSU would not turn on then. 90% sure PSU itself is bad.

KP84 · December 2005

but it worked with the same psu without the case

Donut · December 2005

Did I read correctly the psu blew the fuse with the switch on combined (12v rails) but worked o.k. when you set it to split the 12v rails?

I'm also thinking the psu is bad. You should be able to return or exchange it. (I am assuming it is new)

KP84 · December 2005

Yeh, but now it blows the fuse combined or not.
I dont much about fuses but im jus putting a ordinary 13A in the plug

ryko · December 2005

let me see if i get this straight...

inside case = blown fuse

outside of case = works fine (and btw, you need to put the mobo on a non-conductive surface like cardboard instead of the bare carpet)

sounds like something in your case (i.e a STANDOFF) is shorting out the sytem and blowing the fuse. you used standoffs right? you know they are little brass things which screw into the case and then the mobo goes on top of them. if you forgot them, then the mobo is shorting out on the back of the case and blowing the fuse....if you did use standoffs, then you need to make sure all of them are lining up properly with the holes on your mobo and that none of them are touching any other spot which could cause it to short.

KP84 · December 2005

Yes ive put the standoffs in the rite place and im sure of that, but what ill try is, ill take the mobo out again and check if it works and i forgot to mention i didnt actually put it on bare carpet i used the mobo box. Im sure that somthing is causing a short circuit. Could it be the IO panel? Ive used the standoffs but normal screws

ryko · December 2005

I/O shield could be causing a short....did you bend the tabs on it back so that the ports on your mobo can easily fit? if one of those little tabs on the I/O shield is touching the inside of a USB port or something it could cause a short.

profdlp · December 2005

KP84 wrote:

...I'm just putting a ordinary 13A in the plug

The label on the PSU says to use a slow-blow fuse. This prevents a brief power spike (like when you first turn the system on) from blowing the fuse. If it's a clear glass fuse you will probably (though not always) see a spiral of wire inside the fuse if you have the right one.

KP84 · December 2005

From the other Tagan psu's it says 115-250 Vac mine says 115-230Vac could that be the problem (im from uk)

bothered · December 2005

I still don't understand how a fault on the PC side would cause the main plug fuse to blow. The PSU should have protection against this happening. The fuse will blow for either of two reasons, 1, there is a short on the mains side in which case the fuse will blow straight away or, 2, it's overloaded in which case it may take some time to blow. What else is this plug feeding? A 13A plug top fuse is rated @ 1.2 which means it'll blow @ 15.6A, if say it was a fault on your 12V line you'd have to pull 187A! I don't think its possible. When you connected it on the mobo box was everything else plugged in?
And 230V or 250V doesn't matter. The supply Voltage is only a nominal number.

KP84 · December 2005

All that was plugged in was the ram, processor, fan when i connected it on the mobo box. But im gona try it again rite now, and ill post what happens

KP84 · December 2005

Ok ive set it all up and everything works without the case

:):):):) so i jus need to find a short circuit somwhere, Ill post some images if you guys wona see

Riddick · December 2005

ryko wrote:

let me see if i get this straight...

inside case = blown fuse

outside of case = works fine (and btw, you need to put the mobo on a non-conductive surface like cardboard instead of the bare carpet)

sounds like something in your case (i.e a STANDOFF) is shorting out the sytem and blowing the fuse. you used standoffs right? you know they are little brass things which screw into the case and then the mobo goes on top of them. if you forgot them, then the mobo is shorting out on the back of the case and blowing the fuse....if you did use standoffs, then you need to make sure all of them are lining up properly with the holes on your mobo and that none of them are touching any other spot which could cause it to short.

i agree with ryko's view.. i've heard of shortcircuits caused by these standoffs in the case.. especially with dry weather conditions that promote static electricity.

solution : try adding some form of insulator on top of each standoff before placing the mobo on top and screwing it in. ive used cellophone tape before and it worked like a charm, just cover each standoff with a strip of cellophone tape and screw the screws in through the tape. also, ensure that each screw you use has the rubber stopper that prevents any current from flowing from the top of the screw to the mobo!

hope that helps!

KP84 · December 2005

Yeh thanks a lot for ur help everyone, but i didnt recieve any robber stoppers

Somone told me it dont work in the case cause my friend has the same system except a different case and he doesnt use the rubber stoppers and it works, he told it me its the earth wire of the psu and thats y it keeps blowin? could it be that???

ryko · December 2005

what's the earth wire? you mean the ground wire? as in the black wires from your psu? every psu has about 15-20 ground (blk) wires coming from it so i am unsure of what you mean by earth wire....

anyway, do you have a digital multimeter? if not, i would invest in one---they can be found for as little a s $10 if you look around. they are great for troubleshooting. use the DMM to check the output voltages on your psu when it is connected to the wall by itself. and also check a spare molex when everything is hooked up (outside of the box). you need to write down the values for each rail (or wire color) and post the results here...should be like so...

psu alone...

red = 4.9v
yellow = 11.8v
black = 0.0v
green = 3.2v

w/ mobo/cpu/ram...

red = 5.1v
yellow = 12.1v
black = 0.0v
green = 3.3v

might want to use a DMM to measure actual voltages at the wall socket also. test a few other wall outlets in your house so you can compare values...post those results too.

oh yeah...in order to start the psu when nothing is connected to it, you need to "jumper" the green wire and any black wire on the 20/24pin atx mobo connector with a paperclip or something. then the psu will start and you can test a spare molex or other connector.

KP84 · December 2005

Thanks again. But I was testing what could be wrong and everything worked so i went to screw the psu into the case, I did 3 of the 4 screws (mains was off) and when I was screwing the last 1 in, the psu sparked. So some reason this last screw is causing a problem in the psu

But its not a problem as 3 screws will surely hold the psu in the place and now the computer works fine inside the case

THANKS for your help everyone!

Fuse in main plug keeps blowing!!!

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