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power supply faulty

Marius Ghita

Dec 22, 2014
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Dec 22, 2014
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Hi guys I need your help please

I have a power supply faulty and I am trying to fix it, but I need some advice. My main power capacitors are fried , but I can't find the capacitors , are really hard to find , can I use a lower capacitance or higher?
The capacitors that are fried are primary side:
1600uf 250v dc
can I replace it with 1500uf 250v dc or 1800uf 250vdc
please let me know if you have any ideas.

Thanks Marius
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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Hi Marius and welcome to Electronics Point :)

Are you sure they're 1600 µF? They would be pretty big! Can you show us a photo?
 

Marius Ghita

Dec 22, 2014
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Dec 22, 2014
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Hi

this is the cap x2
80mm circumference
45mm hight
it's a atx power supply 1050w
the value of the caps reads around 750uf
 

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KrisBlueNZ

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Yeah, I think the 1600 µF marking is a lie. At that size, even 750 µF is a lot.

Why do you think they're "fried"?
 

Marius Ghita

Dec 22, 2014
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Because I have other capacitors that are biger than this once and the value reading quite close.
The 10.000uf 50v reads 10.060uf ok
the 470uf 200v reads 473uf ok
but this once should read close to 1600uf so this is how I came to the conclusion that this is the culprit of the fault.
Hopefully someone can help me .

Thanks Marius
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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You would normally expect the measured capacitance to be close to the printed value, but with components from certain countries, you can't necessarily believe the numbers.

If both of them measure 750 µF the power supply will still work. And mains filter capacitors don't fail very often. It's much more common for the output filter capacitors to fail.

What is the fault with the power supply?
 

Marius Ghita

Dec 22, 2014
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Dec 22, 2014
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It's not starting even if I short the green and black. I've checked all the caps on the primary side and diodes and all the mosfet, now the interesting part comes in the short happened at one of the primary mosfets because I can see the marks on pcb but it reads ok the only component i can't measures is the 8 pins chip
 

Marius Ghita

Dec 22, 2014
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Dec 22, 2014
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Hi krisbluenz
I have tried to make some pictures but I get home late and there isn't natural light to make them that good like in tutorial. I will do it after Christmas when I'm off.

Thanks
 
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