Grounding Question - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 30th December 2009, 04:03 PM   #11
diyAudio Member
 
Join Date: Dec 2009
Quote:
Originally Posted by Rodeodave View Post
O
Earth-ground is basically the same as the neutral, but more locally.
In my house, neutral and earth ground both go directly to ground. Literally, I've checked at the panel, traced the wires: they all go to ground.

Quote:
People around here usually connect the circuit-ground via a CL60 type thermistor to the (chassis) earth-ground. The CL60 has a resistance of 10R at roomtemp, providing some damping to eventual ground-loop currents.
Noted. I was wondering how people isolate ground loops away. Thank you for this!

Joe.
  Reply With Quote
Old 30th December 2009, 09:28 PM   #12
diyAudio Member
 
Join Date: Jun 2005
Location: Dallas, Texas
Quote:
Originally Posted by joekraska View Post
In my house, neutral and earth ground both go directly to ground. Literally, I've checked at the panel, traced the wires: they all go to ground.



Noted. I was wondering how people isolate ground loops away. Thank you for this!

Joe.
THe neutral is supposed to connect to earth ground at the panel. So is the
earth ground that gets distributed through the house (ie. the bare wire in all
the boxes that are connected to the third pin of the outlets).

When you say you're getting a shock - is this a small static tick because it's
winter and you've got a high static environment (ie carpets) ???

If not, unplug that thing and get someone who knows what they're doing
to look it over for you.

Your downside - or rather the downside for every person or pet that has
physical access to this thing - is death, in the case the hot is connected
somehow to the chassis.

You've said that you've figured out the ground pin of the (IEC ??? ) socket
is not connected to the earth ground of the power outlet in the wall because
there is only a 2-prong plug. Get this fixed as a matter of course by
just using a proper 3-conductor power cord. (I think I read before that there
is a 3rd pin on the equipment side that is not being used because it's just
a 2-wire cord ????)

IF then you see that proper grounding results in a blown fuse, you will have
figured out that you're lucky noone is dead because the hot will have been
indeed shown to be connected to the chassis. In this case, just figure out
where the short is, and your problem will be probably forever banished.

Good luck and be careful. You really do have a potential tiger by the tail
here. (little engineer humour there - how do you like that one Nelson????)

(I can see it now----- diyAudio: Our jokes are not like your jokes
bum bum bum bum !!!!!!)

Last edited by wayne325; 30th December 2009 at 09:31 PM.
  Reply With Quote
Old 30th December 2009, 09:47 PM   #13
diyAudio Member
 
Join Date: Jun 2005
Location: Dallas, Texas
Quote:
Originally Posted by AndrewT View Post
no.
The third pin in your connecting socket must be permanently connected by a direct wire to the chassis. ALWAYS, no exceptions.

The Chassis must be connected to the house Earth system whenever the equipment is plugged into an outlet socket.
Little clarification here. What Andrew says is correct.

Where the CL60 is used to "isolate the ground" is as a series element between
the signal ground of your audio circuit and the chassis ground that is
connected to 3rd pin of the IEC socket.

So....

net1 - note all at same potential:

wall outlet ground pin, connects to
ground wire of power cord, connects to
ground pin of equipment IEC socket, connects to (use thick wire - at least 18 ga)
equipment chassis, connects to
pin 1 of CL60

net2 - note all at same potential:

pin 2 of CL60, connects to
signal ground of audio circuit


Since net1 is nominally at ground potential, if there is a short from hot,
a large current will flow and the potential of the chassis will probably rise
to about hot/2 until the fuse/breaker blows and then the chassis will return
to ground potential. You want the thick wire I wrote about so that this wire
can carry enough current long enough that the fuse blows before the wire
melts into separate parts. If the ground wire melts before the fuse blows,
it's open season on all who touch the chassis as it is now at hot potential.
In many parts of the world (UK and Europe, HK, others???) this is 240V and
can, ummm, hurt a bit. Or worse. Even in NA it's pretty nasty at 120V.
  Reply With Quote
Old 31st December 2009, 05:07 AM   #14
diyAudio Member
 
Join Date: Oct 2009
You asked for pics...here they are.

This first one shows the IEC socket and the earth pin that is not attached to anything.
Click the image to open in full size.

This one shows where the circuit is grounded to the chassis.
Click the image to open in full size.

more!
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 31st December 2009, 11:09 AM   #15
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
You need 2 grounds to make your amp safe:

1. Safety earth. The chassis should be connected to the mains supply earth (that 3rd pin on the IEC). Then you use a 3 core power cord so that the chassis of the amp is actually connected to your household earth (the spike in the ground somewhere outside your house), ie the 3rd pin on the chassis IEC socket is actually connected via the power cord to the 3rd pin on your wall socket.

In the event that you have a short from the live to the chassis, the current will flow to earth through this wire (until the fuse blows). If you do not have this, then the current flows through you and you die.

2. Circuit ground. This is where all the signal grounds within the amp (what you connect to speaker ground) tie together, star ground. It is normal practice to connect this star ground point to the safety ground. In some cases this causes hum. In those cases it is normal to insert either a CL60 between the signal and safety grounds or you can use a pair of diodes wired back to back, with a 10R power resistor and 0.001uF cap in parallel. Either option should stop the hum.

Please don't take chances with this, you are in a potentially () life threatening situation here.


Fran
  Reply With Quote
Old 31st December 2009, 02:21 PM   #16
hates ground loops
diyAudio Member
 
Rodeodave's Avatar
 
Join Date: Dec 2004
Location: in the alps
Blog Entries: 1
I suppose the lug in the last picture is where the circuit-ground is connected to the chassis. It seems to be a single screw in a threaded hole of the baseplate.

This is not done properly. You need a bolt that goes through the baseplate, a star-washer and two nuts. As this will also be the point where the chassis meets the earth-wire from the socket, this must be a secure connection that won't go loose.

From Elliott Sound Products - DIY Audio Articles you should read Power Supply Wiring Guidelines and Earthing (Grounding) Your Hi-Fi - Tricks and Techniques.
__________________
Gravity - Making the G since 13.7 billion B.C.
  Reply With Quote
Old 31st December 2009, 05:46 PM   #17
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
Quote:
Originally Posted by joekraska View Post
In my house, neutral and earth ground both go directly to ground. Literally, I've checked at the panel, traced the wires: they all go to ground.

Joe.
This is the correct way for the US/NA system. The neutral wires and the ground wires connect together at the main breaker panel (and only at the main panel). All the current travels through the neutral wire, the only time the ground wire carries any current is when something bad happens. Inside your unit the ground wire is connected to the chassis, the neutral wire is NOT connected to the chassis.
__________________
Kevin
  Reply With Quote
Old 31st December 2009, 06:14 PM   #18
diyAudio Member
 
Join Date: Dec 2009
Quote:
Originally Posted by Speedskater View Post
This is the correct way for the US/NA system. The neutral wires and the ground wires connect together at the main breaker panel (and only at the main panel). All the current travels through the neutral wire, the only time the ground wire carries any current is when something bad happens. Inside your unit the ground wire is connected to the chassis, the neutral wire is NOT connected to the chassis.
Yes, I'd gathered that. Up until the point where I'd learned this, I thought I knew something about electricity. This was several years back, when I decided to DIY a subpanel into the garage for a 220v table saw. I was curious enough that I had to go out and read about how AC electricity works: 3 phase, etc.

It's amazing more people don't burn down their houses, knowing what I know now. For example, I have this receptical in our bathroom with a neutral fault. Who knows how that happened? Nail? Anyway, when I was testing it, it occurred to me that hot and ground made a circuit, and that you can actually run it that way. You shouldn't, but can. "Can" as defined by "it will work," and shouldn't is defined by "that might down your house." As the case may be.

But there have to be people out there who've borrowed a (often uninsulated) ground to make a neutral, don'tcha know.

Joe.
  Reply With Quote
Old 31st December 2009, 07:26 PM   #19
diyAudio Member
 
Join Date: Oct 2009
Ok, I have the chassis grounded to the IEC ground. Now, I need to ground the circuit.

I have a 10R 5W resistor here. Can I just put it in between the circuit ground wire and the chassis, or do I have to have the diodes and the capacitor? IE: can I put the just resistor in now and wait for the thermistor to arrive? Or does the circuit require the diodes, capacitor, and resistor?

Thanks for everyone's responses, I'm learning a lot and feeling a lot safer about my venture into DIY hi-fi audio.
  Reply With Quote
Old 31st December 2009, 08:01 PM   #20
alazira is offline alazira  United States
diyAudio Member
 
alazira's Avatar
 
Join Date: Jun 2007
Location: Las Vegas
Blog Entries: 1
Quote:
Originally Posted by bigbillc View Post
Ok, I have the chassis grounded to the IEC ground. Now, I need to ground the circuit.

I have a 10R 5W resistor here. Can I just put it in between the circuit ground wire and the chassis, or do I have to have the diodes and the capacitor? IE: can I put the just resistor in now and wait for the thermistor to arrive? Or does the circuit require the diodes, capacitor, and resistor?

Thanks for everyone's responses, I'm learning a lot and feeling a lot safer about my venture into DIY hi-fi audio.
Hi Bigbillc,
I would not use the resistor by itself. In fact, if you do not have ground hum with the circuit ground wire direct to the chassis, then you do not really have to do anything else.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Question about Star Grounding voivodata Tubes / Valves 2 20th March 2007 07:46 PM
Grounding problem question? excetara2 Solid State 5 10th November 2006 04:39 PM
Power grounding question falcott Chip Amps 0 21st September 2004 07:50 PM
grounding question skyraider Chip Amps 1 9th March 2004 09:12 AM
LM3886TF Grounding Question mothman Chip Amps 1 4th May 2003 11:42 AM


New To Site? Need Help?

All times are GMT. The time now is 03:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2