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Old 22nd February 2010, 12:12 PM   #1
Jasp is offline Jasp  Netherlands
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Default Elco's defect? (Fuse keeps blowing)

Hello all,

A few months ago is started building an amplifier with a 500W PSU: http://www.unisonus.com/pdf/amp_supply.pdf.
The PSU worked great for several weeks until I destroyed my amplifier that was attached to it. (During measurements)

Now one of my 5A Fast fuses keeps blowing, and I'm not sure why. (Testing it with the amplifier disconnected) I tested all diodes and they seem fine. I'm not sure if my elco's are fine though. I'm using two 15000uF Elco's. I only have a multimeter right here to test them. I know you can sort of test them by measuring the resistance, I did this with my multimeter set to 20K. The resistance keeps building up, but it goes very slow when I reach 3K... Seems obvious as the elco's are 15000uF...

So now I'm stuck with a defect PSU, I don't know what it causing it. I'm using a soft start system which still is working. So that can't be it. I hope some of you might be able to help me with this problem, I will really appreciate it.

Kind regards,
Jasper
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Old 24th February 2010, 02:55 AM   #2
gootee is offline gootee  United States
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Have you tried testing the caps separately (disconnected from each other), and comparing? Do you have any other caps to try in their place?

Tom
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Old 24th February 2010, 10:26 AM   #3
Jasp is offline Jasp  Netherlands
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Quote:
Originally Posted by gootee View Post
Have you tried testing the caps separately (disconnected from each other), and comparing? Do you have any other caps to try in their place?

Tom
Disconnected them both and did the same measurement, i.e. with the multimeter. The resistance for both caps keeps climbing. I stopped measuring when they both reached 8K with the multimeter set to 20K.
Does this mean they are both ok?

Haven't got any other caps atm, these caps cost me 25$ , didn't plan to destroy them. Ordered some new ones though for 3$ each at another site. Should arrive next week.

Thanks for the help btw

Jasper
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Old 28th February 2010, 01:12 PM   #4
Jasp is offline Jasp  Netherlands
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Join Date: Oct 2009
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Received the new caps yesterday, installed them today and tested my PSU.
Yet again, the fuses blow

Really confused now, soft start system still seems to work, diodes seem fine, caps are new, what else can there be defect...
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Old 4th March 2010, 07:29 PM   #5
Jasp is offline Jasp  Netherlands
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Join Date: Oct 2009
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Seeing the thread about a broken toroid, I think my toroid might be broken too.
As there is a little black spot on the toroid, so that could be it? (will measure resistance of primary and secondary windings tomorrow)

How is it possible to destroy one though? I'm using a 500VA transformer with 2x 55V 4.55A secondary windings. I use 5A Fast fuses for the secondary windings and one 3A slow for the primary. Am I doing something wrong here? Or is it just a bad quality toroid?

Transformer: Nuvotem | Transformers | Transformers | Toroid Transformers | Open Style with Leads, 15VA to 1000VA |0500P1-2-055

I have one year warranty though, so I think I could just contact them to fix this one or send me a replacement. (As long as I didn't "use" him wrong)


Jasper
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