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Old 31st July 2005, 01:25 AM   #11
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Quote:
I don't think that you see my point. (Maybe there isn't one at all..)
I'm sorry..I don't see your point. Seeing that my name is NOT Nelson Pass, I am no expert either. But, my opinion is that:

The center bolt on any toriod in pretty much any amp is attached to the chassis, ..why is mine different? Whether it has been deemed star ground <or> not, it is still a point that IS ground. If everything around it is insulated, where is the danger?

Don't get me wrong here. It is possible that I am being stubborn and pigheaded, and am blind to the issue. If so, help me someone..I don't see it!

Thanks,
Marc
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Old 31st July 2005, 01:48 AM   #12
Illusus is offline Illusus  Canada
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I don't understand your drunken logic either .
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Old 31st July 2005, 02:34 AM   #13
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Quote:
Originally posted by mpmarino
why is mine different? Whether it has been deemed star ground <or> not, it is still a point that IS ground. If everything around it is insulated, where is the danger?
If the bolt throu the middle is connected to the chassis at both ends (ie bolted to the chassis at the bottom & the top is used as a star ground at the top with wires over the top of the toroid, you have created a shorted turn. Not a good thing -- will cause premature death of the amp..

And from this pic it indeed looks like you have done that.

Click the image to open in full size.

dave
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Old 31st July 2005, 03:21 AM   #14
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TroelsM,

If this is what you meant by 'shorted turn', then I now see what you are talking about... I had no idea. Thanks for pointing that out.

Dave,

Thanks for helping to drill that into my thick skull.

I am still not clear on where the 'short' would occur, but I can get a grasp of what 'could' happen. I've got to think about this for a while. It's nice to learn something new....

edit...
It seems the easiest way to open the shorted turn would be to isolate the bottom of the bolt from chassis and run a ground over the top to star. This would remedy it..right?
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Old 31st July 2005, 03:29 AM   #15
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Quote:
Originally posted by mpmarino
It seems the easiest way to open the shorted turn would be to isolate the bottom of the bolt from chassis and run a ground over the top to star. This would remedy it..right?
yes. That would fix it.

When i mount a toroid i go the extra step and use a nylon bolt or just use zap-straps to attach to the chassis.

dave
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Old 31st July 2005, 03:34 AM   #16
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Thanks guys,

I usually learn the hard way. In some ways that is good, because it's difficult to forget what was learned. This is gonna be a pain in the butt to fix! Oh well.
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Old 31st July 2005, 06:17 AM   #17
Stones is offline Stones  United States
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Quote:
Originally posted by mpmarino
TroelsM,

edit...
It seems the easiest way to open the shorted turn would be to isolate the bottom of the bolt from chassis and run a ground over the top to star. This would remedy it..right?
Use a nylon bolt for isolation or move your ground point to a different location. Excellent job on the case
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Old 31st July 2005, 01:19 PM   #18
TroelsM is offline TroelsM  Denmark
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Default back with only a small hangover...

Hey.

I'm glad that someone understood my drunken arguments.. I think its a big mistake to use the bolt for any other purpose than mounting the torroid.

To see why the center-bolt could be a bad place for the star-GND think about this scenario: You connect the amp to a pre-amp with a normal shielded phono-cable. The shield now connects your star-GND to the GND of the pre-amp (in most cases..). If the two chassis touch each other and make contact you would "melt" something because of the very high currents running in the "short". Actually the Poweramp would probably survive and the current would destroy the phono-cable or something in the pre-amp.

Hope you se my point. (Still hoping that there is a point.. )

Cure: Make a new ground-point somewhere else on the chassis and use that instead of the transformer-bolt.

TroelsM
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Old 31st July 2005, 04:18 PM   #19
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Quote:
I'm glad that someone understood my drunken arguments.. I think its a big mistake to use the bolt for any other purpose than mounting the torroid.
I do understand and I apologise if I was a bit 'flip' in my response. I was ignorant of the issue. I have fixed the problem and the bolt that mounts the toroids has been 'interrupted' by a 3/8' threaded phenolic ground isolator. The loop is broken. A wire has been taken from star to earth at power entry. This was the only way I could fix it without a re-design. Thanks for your sharp eye! I feel better now.

Marc
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Old 1st August 2005, 02:34 AM   #20
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haha, I get it now too! Now who's the fool!? This guy (poinintg at myself)

I just caused the same problem in one of my amps by trying to shield it with copper ribbon. It got pretty f'n hot.
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