Author Topic: bad output on my homebrew psu  (Read 473 times)

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Offline m3vuv

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bad output on my homebrew psu
« on: January 29, 2020, 05:41:56 am »
Hi all,ive a 0-30v  o-20amp psu,the output looks like a sort of 3phase ac signal on my scope,if i put a .1farad cap on the psu output the trace is flat dc,does this indicate bad filter caps or a bad diode in the brige rectifier?,cheers in advance.
 

Offline m3vuv

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Re: bad output on my homebrew psu
« Reply #1 on: January 29, 2020, 05:44:48 am »
heres the cap im testing with on the psu output.Its 100.000uf at 50v.the original filter caps i used were 4x 3000uf  but chinese
 

Offline xavier60

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Re: bad output on my homebrew psu
« Reply #2 on: January 29, 2020, 11:27:06 am »
What is the ripple frequency? Is the ripple present while the PSU is unloaded?
Is there a schematic of it?
« Last Edit: January 30, 2020, 07:19:22 am by xavier60 »
Hioki AS100D vom, HP 54645A dso, Fluke 87V dmm, AN8008 dmm, Agilent U8002A psu,  FY6600 function gen, New! Brymen BM857S-(With Battery)
 

Offline m3vuv

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Re: bad output on my homebrew psu
« Reply #3 on: January 29, 2020, 01:44:39 pm »
i dont know the ripple frequency yet as havent meashured it,its there all the time loaded or not tho.
 

Offline xavier60

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Re: bad output on my homebrew psu
« Reply #4 on: January 29, 2020, 10:04:11 pm »
Why does the oscilloscope trace have bright and faint segments?
Hioki AS100D vom, HP 54645A dso, Fluke 87V dmm, AN8008 dmm, Agilent U8002A psu,  FY6600 function gen, New! Brymen BM857S-(With Battery)
 

Offline m3vuv

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Re: bad output on my homebrew psu
« Reply #5 on: January 30, 2020, 03:46:22 am »
its down to the shutter on my phone camera,its ok in reality.
 

Offline schmitt trigger

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Re: bad output on my homebrew psu
« Reply #6 on: January 30, 2020, 04:16:53 am »
-No schematic or basic circuit description.
-Ambiguous problem description and troubleshooting.
-Poor quality and not useful images.

It will be *very* difficult to provide you with an accurate advice.
 

Offline tkamiya

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Re: bad output on my homebrew psu
« Reply #7 on: January 30, 2020, 05:13:33 am »
You have your scope set up on AC coupling.  So what you are seeing is not the entire output.  You are seeing fluctuation of your output.  DC offset is not part of the display.  I see your scale setting is at 2V.  Whatever is happening is not normal.  I'd say your power supply is oscillating. 

Please either describe your post your circuit. 
 


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