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Bang and spark at the end of the kettle plug type lead

mij

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#21
Thanks KenB for coming back on this.

you asked "Do you have a volt-meter to test the output of the new power supply ?"
Yes, What would you like to measure as it looks as if there is a variety of voltages in the power supply - but most seem to be low in value.
Jim.
PS. I have ordered an adapter lead that changes the 4 lead plug (it is a male on th power supply) it changes the 4 plug to an 8 which will fit the Mo-Board. It says the yellow leads are 12V and 22A. The other wires (black) are grnd.
 
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mij

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#22
I tried the output on what the blurb says is the mobo feed of two yellow wires which should be 12V. Nothing! So I assume the power supply is suspect and remove it for further investigation. The mains feed is ok, there is 240V at the end of the cable. I did try the switch on the power supply in both positions as it did not read off/on. I assume its fan should run anyway.
Jim.
 

KenB

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#23
Hi Jim

I wrote an article a few years back on how to test a PSU.
See here - Test a Power Supply Unit - Free PC Help Magazine

From what you say re: the yellow leads your PSU is suspect as you say.
I suspect that you will have a 24 way connector [ alternative is 20 ] so refer to the appropriate section of the tutorial.

Take a photo if you need to of where the connections are.

Unplug all of the PSU leads from the motherboard and other hardware.
 
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mij

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#24
You are correct as it is a 24 pin plug.
There is no life (no voltage reading) on the red or yellow wires/connections.

I'm wondering why it has to be in the main casing as before I fit the next one I was going to plug it in and see if the fan worked - wouldn't this tell me that life was getting to the PSU? I assume that the PSU is earthed through the mains plug - or can we not rely on that?
Jim (not an electrician obviously).
 

KenB

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#25
I assume that the PSU is earthed through the mains plug
Yes it is Jim - leaving it in the case assumes that the PSU being tested is already mounted in the case
and there is no need to remove it for testing.

The PSU fan rotating simply indicates that power is getting to that part of the PSU.
The voltage check on the 24 way connector checks out the 12v and 5v and 3.3v wires.

Are you checking the old or the new PSU ?
[ I thought it was the new one :) ]
 
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mij

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#26
Yes it is the new one which I'd fitted in the casing - wasn't I optimistic :). I am not going to couple up the old one again, I don't like sparks and bangs.

Ok another on order, send this one back! Oh dear me, what a palaver!
Jim.
 

KenB

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#27
When you get the new one check it out before you put it in the case.
Just plug it in to see if the fan rotates and check that the 12v supply is working.

I hope that there isn't a problem within the case causing the PSU problems.
 

mij

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#28
Thank you for your response KenB. It is good to know that someone is there :).

You said "I hope that there isn't a problem within the case causing the PSU problems"

I also hope all is well within the computer case as well, it might also cause another PSU to give its final volts.
It might mean that I'll have to get a new desktop after all. I am unsure if I can get another with W7 in it though. Mind you I could always rebuild this desktop here :).
Jim.
 

KenB

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#30
I am unsure if I can get another with W7 in it though.
I doubt you would find a new machine with Win7 - you may have to look for second hand / re-furbished machine
or a version of Win7 CD that has not been used.

The fans are not turning and nothing is lighting up
This would seem to indicate a PSU / motherboard problem NOT a RAM / Hard-drive or VideoCard problem.
This hardware could well have been damaged too BUT the symptoms explained indicate a PSU or Motherboard

Let's see what happens with a replacement PSU :)
 
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mij

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#31
The new PSU arrived today. I have plugged it into the mains and the fan does not turn at all.
Not very inspiring! Shouldn't it at least run the fan?
Jim.
PS I have checked the lead (new fuse) it is ok. Used another lead just to make sure and still not turning the fan.
 
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Rustys

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#32
The new PSU arrived today. I have plugged it into the mains and the fan does not turn at all.
Not very inspiring! Shouldn't it at least run the fan?
Jim.
PS I have checked the lead (new fuse) it is ok. Used another lead just to make sure and still not turning the fan.
No it will not run unless a complete circuit is created. So it has to be plugged in to the Motherboard to complete the circuit.
 

mij

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#34
It is a few days later, I am also a male nurse BTW - unqualified at that :).

I have now plugged in the new PSU and the 24 pin thingy (see photo, the plug is between my fingers) and nothing turns or lights up.
I'm assuming that the mobo is powered by the 24pin plug. Since both PSUs do not work with the 24pin plug connected does this mean the mobo is suspect? I hardly think that 2 PSUs are defective.
Jim.
hand pointing to the multiplug.jpg
 

mij

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#35
I have now tried both PSUs and there is nothing coming out of either. I have double checked the lead/fuse in the mains lead with another electrical item and that proves it is OK. I have also connected both up to the 24 pinned mobo connection and still nothing. I could use Victor Meldrews words here but it's beyond the pale.
Jim
 
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KenB

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#36
Hi Jim,

Unplug the lead to the PSU from the wall.

Take off the motherboard the 24 pin connection.

Locate pins 15 and 16 [ black and green ] and use a metal paper clip or piece of wire to short them out.
[ Connect them together ]
This fools the PSU into thinking that it is connected to the Motherboard.

Plug in at the wall again.

Check the voltages now.
1537123710059.png
 

mij

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#37
Hooray! Getting something. The fan turns on the first new one (saves sending it back) and getting the 12.something volts on the yellow wires :).

The same happened on the second new one too :).

Ok, ready to move on tomorrow and feeling a bit better about it now.

Thanks for that KenB.
Jim.
 
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KenB

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#38
Hi Jim,

Check the voltages on the 12v - 5v - 3.3v wires. [ There are negative voltages on a couple ]
Check that the "Ground" wires are not reading any voltage.
The recorded voltages should be pretty close to the diagram.
Make a note of the pin number and the voltage recorded.

If the PSU checks out OK - unplug from the mains - and remove the shorting link.

Take the RAM out of the Motherboard and remove the Video Card too - if you have one.
Remove any other cards that you may have [ Sound ? - Network ? - etc ]
DO NOT remove fans - just hardware that is plugged in to the Motherboard.

Also remove any leads connected to the Motherboard from the Hard Drive / DVD etc.
Make a note of where they were removed from.
Disconnect any external devices - monitor / printer etc.

Still with the PSU unplugged .....

Check the Motherboard for burn marks or blown capacitors.

1537191315448.png

If there are no obvious problems [ burn marks / capacitors ] then ......

Assemble the PSU into the computer casing [ don't connect any of the cables yet ]
Connect ONLY the 24-way socket to the motherboard.

Be VERY careful here as you said that you got sparks etc .......
Switch on at the wall.

The PSU fan should spin and the Case Fan / CPU Fan should spin.
 
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mij

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#39
I have done that and all was correct except pin 20 that had no connecter in it - this was also true of the old PSU taken out.

The results are as shown in the photo. I had to use a work around for that as the FUJI camera did not show in the scan photo box. Only the printer scanner. It worked ok before. I hope I can add it and you can enlarge it.
Jim.

Voltyages out of PSU.jpg
 

KenB

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#40
Hi Jim - those voltages look OK.

The -5v [ no connection ] is nothing to worry about.
Some of the very old motherboards used it - but not modern ones.

I have added to my previous post for what to do next.