No power....clicking noise

[yankor]

hi guys


I went away for a few days and turned the computer of normaly,then removed the socket from the wall..
Got back yesterday,pluged it in and its dead!! there is a flickering green light(at the back)under the power supply cable but no other sign of power anywhere...theres also a continuous clicking noise that seems to be coming from the power supply unit.


anyone any ideas?

thanks

Compaq presario
intel pentium 4-3 ghz
1 gb ddr-160 gb hd

 

[yankor]

thx,whanula and ace.

Got the meter.
I have been reading up a bit about testing the psu with the meter and just have a couple of quistions.

is it best to test the psu free from case(all connectors disconnected)or with connectors in place?

any tips or good links that could help me??

thx

 

[sjs1717]

good for you...... i would think you need to disconnect everything (as you don't want voltage sent to the board in some spots and not others) then you are in total control of everything


Steve
We're doing this stuff for the wealth and fame right?

 

[sjs1717]

I'm sorry Yankor i misread your question leave the unit in the case but disconnect all the connectors. now you know what pin supplies what voltage if there is an absence of voltage the truth will come out.......a meter is a great tool to have you will use it again


Steve
We're doing this stuff for the wealth and fame right?

 

[yankor]

thx steve,but whats the difference with all connectors disconnected and the psu is (in or out of its case?)...surley its the same

i dont realy understand and just want to be clear.

 

[edfair]

With everything disconnected you'll only get voltage for the standby circuits. Should be 1 red wire IIRC and probably any of the blacks for 0, although it has been a while. Try a google search for "ATX wiring diagram" to see if you can find where things connect.

And once you have the wiring you'll see the pin you'll need to connect to 0 to bring up the rest of the power. Think it is on 14 (usually green) and it connects to one of the blacks.



Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[yankor]

thanks ed.


So i went ahead and tested the psu but somthing stranged happened.I followed these steps

http://www.ochardware.com/articles/psuvolt/psuvolt2.html

1st i tested the 12v line on the PSU's motherboard connector and the meter ran from 11.8 and descended 0.01 in about 25 seconds,dead?doudle checked i was doing every thing right i tested it again and got a solid 11.8(did not budge)another test and it ran from about a 8 to 0 and its still like that until now.

The test wher i got a solid 11.8 the green psu light was on but now thats disappeared.
any ideas anyone?

 

[edfair]

If this is happening with the power connectory plugged into the M/B it is usually an indication of a crowbar shutdown. Which is kinda what we have been dancing around all this time.

I would suspect that you'll see the fans try to crank up as the 12 tries to come up to voltage. In most cases with a dead short they get about 1/4 turn.

Either your power supply is sensitive, or there is something on the M/B shorted or partially shorted that is drawing enough to trip the crowbar.

Might be time to look for bulging capacitors.

I'm not sure on your machine whether the 12 should remain on. That would be to keep the fans running if the box was hot. You are supposed to be looking at the 5v for the standby circuits. Standby should come up and stay up. The others should momentarily come part way up for the duration of the standby circuit working to shut them down.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[yankor]

If this is happening with the power connectory plugged into the M/B it is usually an indication of a crowbar shutdown. Which is kinda what we have been dancing around all this time."


Everything was disconnected from the M/B when i done the test.
I also looked at the bulging capacitors in the psu,some had a yellow plastic substance(glue?)all others seem fine.

does this change anything?


Today i had all but the 20 pin connector attached to the M/B,i shorted the green and grnd wires and there was power-the psu fan was running-the 2 drives working-the HD spun but the two others fans were dead... its realy nice to see some power

Is my psu still the suspect?

 

[edfair]

It can still be the M/B or the P/S. But if there was bulging of the capacitors in the P/S then my prognosis is leaning towards it.

You are in the unfortunate position of entanglement with one of Murphy's laws. Given the choice of replacing one suspect part, you'll inevitably choose the wrong one. The countervailing collary states that if you choose the one less likely to be bad, that will be the one time when Murphy's law didn't apply.

You can't really appreciate this. Long time computer techs can. It is the story of our life.

You've reached the point where you really need part swapping capability. But I recognize that not everybody can invest that much in spare parts.

 

[yankor]

If this is happening with the power connectory plugged into the M/B it is usually an indication of a crowbar shutdown. Which is kinda what we have been dancing around all this time."

No, Ed. The test was done with all connectors unplugged from the M/B. Does this change your reply?

I also looked the capacitors and there was a yellow plastic substance on some of them (glue?), but all the rest looked fine.

Today I had all the connectors attached to the M/B, except the 20 pin and the 4 pin, which I shorted with the green/grnd wire.

I got power, the PSU fan was running, the HD spun, the 2 drives were working, but the other 2 fans were dead. It's so nice to see a bit of power! ;-) hope it's a good sign...

Does it still sound as if I have problems with the PSU?

Thanks

 

[LawnBoy]

Maybe I'm crazy, but I would swear that I've worked on PSUs that would crowbar if they had no load present. I.E., unplug from M/B, no voltage, plug into M/B, voltage.

Is it Alzheimer's?


"We must fall back upon the old axiom that when all other contingencies fail, whatever remains, however improbable, must be the truth." - Sherlock Holmes

 

[acewarlock]

Yes there are PS that won't work unless there is something plugged in to it like a HD or MB.




This is a Signature and not part of the answer, it appears on every reply.

This is an Analogy so don't take it personally as some have.

Why change the engine if all you need is to change the spark plugs.

 

[edfair]

Yeah, some go overvoltage shutdown if they don't have some current drawn on the +12 since they use that as the beginning point of regulation.

I think the original IBM PC supply kamikazied itself if it didn't have at least one floppy plugged. Not just crowbar but 45ACP to the guts.

 

[acewarlock]

http://www.howstuffworks.com/power-supply.htm

This is a Signature and not part of the answer, it appears on every reply.

This is an Analogy so don't take it personally as some have.

Why change the engine if all you need is to change the spark plugs.

 

[yankor]

Thank you all for the replys!

I will just have to think a little about my next step...
realy wated to repair this myself but dont have the resources.

thanks again