A quick inquiry to Mr. Thatcher has me intrigued. I noticed Randy experimenting with different
methods of grounding. One was the typical CL-60 bypassed by a cap and the other used a bridge
rectifier as a 'grounding' device. A quick search revealed a post about the bridge rectifier method as far
back as 2007. See post #8 below.
What means ground lift?
And he was kind enough to send me the following link.
Ground Loops
Does anyone have any further info my brief use of the search engine has yet to uncover?
Regards,
Dan
methods of grounding. One was the typical CL-60 bypassed by a cap and the other used a bridge
rectifier as a 'grounding' device. A quick search revealed a post about the bridge rectifier method as far
back as 2007. See post #8 below.
What means ground lift?
And he was kind enough to send me the following link.
Ground Loops
Does anyone have any further info my brief use of the search engine has yet to uncover?
Regards,
Dan
The IEC safety ground connection is never combined with any other chassis connections.
https://electronics.stackexchange.com/questions/422550/proper-chassis-grounding
The bridge rectifier serves to shunt large fault current to the chassis, which will open the fuse.
https://electronics.stackexchange.com/questions/422550/proper-chassis-grounding
The bridge rectifier serves to shunt large fault current to the chassis, which will open the fuse.
IIUC, so long as the AC line ground is connected directly in contact with the exposed metal chassis, held down with washers and a nut, then other grounds can stack on top of that same chassis ground stud (or screw) held down with their own washers and nut.
Mt recollection (from somewhere in the regulations) is that only 2 nuts are allowed on the safety ground bolt.
The second nut keeps the first nut tight, and is not to be used for additional lugs.
https://www.boltscience.com/pages/twonuts.htm
The second nut keeps the first nut tight, and is not to be used for additional lugs.
https://www.boltscience.com/pages/twonuts.htm
Maybe its different if its a welded stud? Someone who did the safety design for his company's equipment talked to the various certification agencies and says stacking is allowed if it is done in a certain way.
If you can avoid using a GL, I’d say that’s the best route forward. Although the ‘Ground Loops’ presentation shows how to do it, I gave not used a GL since 2012.
The most important thing, with or without a ground lifter, is that the incoming safety ground goes directly to the metal chassis. If live [hot] or neutral come into contact with the chassis internally because of a fault condition, the safety ground provides protection via the RCD (aka GFI).
A GL if used, only lifts the secondary side common ground - it never lifts the safety ground. Also, never use a GL with an old style fuse box. That is plain dangerous.
The most important thing, with or without a ground lifter, is that the incoming safety ground goes directly to the metal chassis. If live [hot] or neutral come into contact with the chassis internally because of a fault condition, the safety ground provides protection via the RCD (aka GFI).
A GL if used, only lifts the secondary side common ground - it never lifts the safety ground. Also, never use a GL with an old style fuse box. That is plain dangerous.
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Maybe so, when I've tried stacking more than two nuts, they got loose.
But I didn't know at the time whether there was a right way to do it.
a] the Safety Ground/Protective Earth and the transformer screen should be attached to the chassis near where the AC cord enters the chassis.
b] the DC supply common and the audio circuit common should be connected to the chassis near the audio input connectors.
b] the DC supply common and the audio circuit common should be connected to the chassis near the audio input connectors.
Douglas Self discusses this in one of his books and indeed you can wire an amp up with the RCA signal returns connected direct to the chassis. But, there’s a few other things you have to do differently and in a DIY environment, the techniques outlined in the ‘Ground Loops’ presentation linked to above are probably easier to apply universally. For a volume production amp, I have no doubt Self’s method is very good.
Yes, for HF instrumentation it is the preferred way. Some early audio gear designed by WWII veterans did that.
Early Dynas for example.
Early Dynas for example.
Indeed. I had a Marantz PM7000 (now donated to a relative) that used the techniques outlined in the Ground Loop presentation.
And that's where the problems begin. (it's one of Jim Brown's biggest complaints)
The RCA shells should be bolted to the chassis. The commons can be connected thru a resistor or a bridge, resistor, capacitor network.
In Audio Engineering Society Standard AES 48.
A shields should be attached to the chassis at their connector.