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Old 13th March 2006, 06:56 PM   #11
ostie01 is offline ostie01  Canada
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No, I used standards input gold plated with ground attached to the case.I tought that it was better this way, maybe I was wrong.Every cables for input and output is sheilded with the sheild attached to ground.
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Old 13th March 2006, 07:44 PM   #12
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Nope, the sockets should be isolated. I'm afraid it seems you have some major grounding issues to put right.
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Old 13th March 2006, 07:57 PM   #13
ostie01 is offline ostie01  Canada
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HI, thanks for those great reply. What could I do, replace every every connectors.I don't know if I can isolate them from the case, I think I can't.Here's the pic of the RCA connectors I use.


http://img55.imageshack.us/img55/492...nnector2ay.jpg

What is the main reason why those connectors should not be grounded to the case, they will be anyway with the sheild.

Thanks
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Old 13th March 2006, 08:35 PM   #14
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You should only have one ground, and that should be of star formation feeding off to everything that needs a ground. By allowing the sockets to contact the chassis you make multiple ground points which can create eddy currents in the chassis (if steel) but also slightly different ground paths will be present.
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Old 14th March 2006, 03:29 AM   #15
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Hi "Ostie01" (it sounds weird a little bit knowing what it means...)

I agree with Richie00boy. Your RCA input/output jacks should be isolated. You can use the same non-isolated jacks if you do not want to buy new isolated ones. Just increase the size of the holes in the metal chassis so they do touch the RCA jacks at all. Then use an isolating material like plexiglass plate (for example) and fix all RCA jacks to it. Afterwards, just fix your plexiglass plate witch screws to the rear metal chassis. See example in attached picture (sorry for the picture quality...)



Good luck
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File Type: jpg hpim1112b.jpg (39.0 KB, 160 views)
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Old 14th March 2006, 05:58 AM   #16
ostie01 is offline ostie01  Canada
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Thanks, will try out and let you know of the result, Thanks
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Old 14th March 2006, 07:18 AM   #17
ostie01 is offline ostie01  Canada
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Hi, well this not seem to work , nothing changed, same hum.Just remove rca connectors from case , put some electrical tape around to prevent short circuit and still have that hum.

Here's a pic at output of speaker B , sorry for poor quality pic but it's not easy to take picture of a screen.


http://img86.imageshack.us/img86/1015/oscillo5yv.jpg
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Old 14th March 2006, 07:21 AM   #18
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Have you revisited the rest of your grounding scheme, making sure things are starred properly?
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Old 14th March 2006, 07:32 AM   #19
ostie01 is offline ostie01  Canada
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HI, not sure of what you are talking about.Do I have to isolate the two main boards from the case, i.e. there's a ground path that's surround the two boards and the the screws that support the boards are made with metal and touches the ground path around the boards and are screwed to the metal case.Here's another pic with some comments, maybe this can give you a better idea.


http://img90.imageshack.us/img90/925...ssover11im.jpg
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Old 14th March 2006, 08:26 AM   #20
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Hmm that doesn't sound ideal.

Your central ground should be at the centre of your PSU capacitors, then anywhere that needs a ground should have it's own wire from this point. There should be no other paths. This prevents any ground loop currents from forming within the subsystem, but also ensures that one board or whatever putting a lot more current into/out of ground does not influence the other boards grounds.

I think you have some reading up on good grounding principles to do before you attempt any more of this project. Your main issue could be caused by something else, but it is important IMO to get your basics right.
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