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AMB o25 Problems

post #1 of 11
8/24/11 at 9:26am
Thread Starter 

Just put together my second o25 PSU build for 5v output. The PSU delivers 5v (4.94v to be exact) but there is a loud buzz/hum noise when connected to my y2 DAC. I'm all out of ideas, any advice would be very helpful.

Thanks

dean0 

 

 

 

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post #2 of 11
8/24/11 at 1:51pm

Ground loop?

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post #3 of 11
8/24/11 at 6:19pm

WHat kind of measurement do you get when you set your dmm to AC volts?

 

Also, what kind of dmm are you using?

 

Is it possible for you to share a picture of your project?


Edited by digger945 - 8/24/11 at 6:20pm
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post #4 of 11
8/25/11 at 6:01am

sure sounds like a ground loop, but yeah without pics its hard

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post #5 of 11
8/25/11 at 9:11am
Thread Starter 

2011-08-25 17.05.31.jpg2011-08-25 17.07.27.jpg2011-08-25 17.07.41.jpg2011-08-25 17.07.48.jpg

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post #6 of 11
8/25/11 at 12:05pm

Any change if you disconnect the sigma board from AC ground?

 

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post #7 of 11
8/25/11 at 12:17pm
Thread Starter 

nope I tried that already, all out of ideas, could a faulty component cause this kind of problem?

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post #8 of 11
8/25/11 at 3:44pm

Have you thought about posting on AMB's forum???

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post #9 of 11
8/25/11 at 5:13pm

Get rid of the black wire that is connecting the "G" pad on the Sigma 25 to the earth ground.

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post #10 of 11
8/26/11 at 11:51am
Thread Starter 

Tried disconnecting the ground pad wire and reheated all joints, still no luck. I took some more measurements... 5v when I set the DMM to V- 20 but I get 9v when set at V~200 , any ideas?

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post #11 of 11
8/26/11 at 12:05pm

That's why I don't like cheap DMM's (even though I've had the same issue with a bench top 5.5digits Agilent).

 

Try measuring the DC voltage at the input of the regulator under the same conditions (same load, etc). Perhaps the input is too low under load and the regulator can't keep regulating.

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