Power supply filtering

Craig405 · 19th July 2005, 04:52 PM

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

still4given · 19th July 2005, 05:20 PM

How old are your caps? Perhaps you would benefit from reforming them.

Good article on reforming caps

Blessings, Terry

Craig405 · 19th July 2005, 05:32 PM

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.

still4given · 19th July 2005, 05:47 PM

Maybe the bridge is failing. They are cheap enough, try replacing it.

Blessings, Terry

Cortez · 19th July 2005, 05:49 PM

RLC-resonance from parasitic Ls and Cs.
Search for the expression "snubber" at diyaudio!
Wait for your results after the mods !

Leolabs · 20th July 2005, 01:24 AM

U may try choke filtering too

Craig405 · 20th July 2005, 10:28 AM

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

Geoff · 20th July 2005, 10:56 AM

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.

Danko · 20th July 2005, 11:28 AM

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

janneman · 20th July 2005, 11:34 AM

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

19th July 2005, 04:52 PM	#1
Craig405 diyAudio Member Join Date: Jul 2005 Location: Sussex	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

20th July 2005, 11:28 AM	#9
Danko diyAudio Member Join Date: Apr 2004 Location: Hungary	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 __________________ Best regards, Danko

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19th July 2005, 05:20 PM	#2
still4given diyAudio Member Join Date: Oct 2004	How old are your caps? Perhaps you would benefit from reforming them. Good article on reforming caps Blessings, Terry

19th July 2005, 05:32 PM	#3
Craig405 diyAudio Member Join Date: Jul 2005 Location: Sussex	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.

19th July 2005, 05:47 PM	#4
still4given diyAudio Member Join Date: Oct 2004	Maybe the bridge is failing. They are cheap enough, try replacing it. Blessings, Terry

19th July 2005, 05:49 PM	#5
Cortez diyAudio Member Join Date: Dec 2002 Location: Hungary	RLC-resonance from parasitic Ls and Cs. Search for the expression "snubber" at diyaudio! Wait for your results after the mods !

20th July 2005, 01:24 AM	#6
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	U may try choke filtering too

20th July 2005, 10:28 AM	#7
Craig405 diyAudio Member Join Date: Jul 2005 Location: Sussex	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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