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Old 19th July 2005, 04:52 PM   #1
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Angry Power supply filtering

Hi

I have measured the AC component on my power amplifier PSU (which is not switch mode) rails and it is massive, a lot of jagged looking high frequency noise at 5Mhz.
What is causing this?
I have 20000uf per rail plus 100nf caps on each rail and another 400uf of caps per rail on my circuit board.

????????

Cheers
Craig
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Old 19th July 2005, 05:20 PM   #2
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How old are your caps? Perhaps you would benefit from reforming them.

Good article on reforming caps

Blessings, Terry
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Old 19th July 2005, 05:32 PM   #3
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The caps should be ok, the large ones were reformed for a few hours on a bench power supply before use and all current readings were very close to each other once stabilised.

Thanks for the suggestion.
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Old 19th July 2005, 05:47 PM   #4
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Maybe the bridge is failing. They are cheap enough, try replacing it.

Blessings, Terry
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Old 19th July 2005, 05:49 PM   #5
Cortez is offline Cortez  Hungary
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RLC-resonance from parasitic Ls and Cs.
Search for the expression "snubber" at diyaudio!
Wait for your results after the mods !
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Old 20th July 2005, 01:24 AM   #6
Leolabs is offline Leolabs  Malaysia
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U may try choke filtering too
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Old 20th July 2005, 10:28 AM   #7
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Cortez, thanks for that

Ok i am convinced it is parasitic inductance in my wires as some are 1 foot long!
Oh well they are very thick wires (rated for 30amp) i thought they would be ok.

I have looked into snubbers on the search and found out what they are. I think i should add 2 snubbers per rail (+/-), one at the heatsink for my power transistors and the other on my circuit board power rail tracks.
I only need to calculate my R's and C's now.

Can anyone send me this document ?http://www.hagtech.com/pdf/snubber.pdf.
Its a dead link now but people used it on the threads.

Cheers everyone
Craig
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Old 20th July 2005, 10:56 AM   #8
Geoff is offline Geoff  United Kingdom
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Quote:
Originally posted by Craig405

Can anyone send me this document ?http://www.hagtech.com/pdf/snubber.pdf.
Its a dead link now but people used it on the threads.
Email me. I have a copy I can send you.
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Old 20th July 2005, 11:28 AM   #9
Danko is offline Danko  Hungary
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Can I get one of that file too? :-)

I can upload it to my server, and link the file to here.


Thanks in advance, Danko
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Old 20th July 2005, 11:34 AM   #10
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Default Re: Power supply filtering

Quote:
Originally posted by Craig405
Hi
I have measured the AC component on my power amplifier PSU (which is not switch mode) rails and it is massive, a lot of jagged looking high frequency noise at 5Mhz.
[snip]

Craig, what level?

Jan Didden
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