Chassis Grounding and rectifiers - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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
Thread Tools Search this Thread
Old 9th January 2009, 05:33 PM   #1
diyAudio Member
Join Date: Jun 2008
Default Chassis Grounding and rectifiers

I think it's a good idea to ground a chassis with a 3 prong plug for safety reasons. I'm using a bridge rectifier and a regulator on the current build. It just occured to me that I might have a problem in the making.

If I solder the B- to the chassis and then go to ground with a 3 prong plug, have I not shorted out the bridge diode between the AC neutral and the B-, given that the AC neutral and ground are bonded at the circuit box?

Is that question clear? Of the four diodes in the diamond shaped bridge rectifier circuit that we are all familiar with, one of the four stands between the AC neutral and the B-. That's the one I suspect I'd be shorting (through the home wiring) by using the 3 pronged plug.

Is this correct and what are the consequences?

  Reply With Quote
Old 9th January 2009, 05:49 PM   #2
Svein_B is offline Svein_B  Norway
diyAudio Member
Join Date: Oct 2005
Not to reason to worry.

Provided you are using a normal power transformer, the secondary windings are completely isolated from the primary and from ground, ie. floating.

There will thus be no shorting in your amp, nor in any of the other millions in operation with this arrangement.

  Reply With Quote
Old 9th January 2009, 06:08 PM   #3
diyAudio Member
Join Date: Jun 2008
Oh yeah, I forgot to mention that part. No transformer planned; 6GM8s. I'll need an isolation transformer unless I completely isolate the B-? Doesn't sound very safe without one, does it?
  Reply With Quote
Old 9th January 2009, 06:12 PM   #4
Jeb-D. is offline Jeb-D.  United States
diyAudio Member
Jeb-D.'s Avatar
Join Date: Nov 2005
Location: SoCal
You must use a transformer for isolation. Your concern sounds as if you intend to directly rectify the mains which is unsafe. Earth ground is used as a voltage reference. Current will flow from and back-to the isolation transformer. Earth ground will just pull the circuit down to ground potential so that it is not floating.

Neutral and earth ground are tied together, but before the breaker. If current flows in the earth ground, the breaker will trip.
  Reply With Quote
Old 9th January 2009, 06:15 PM   #5
Svein_B is offline Svein_B  Norway
diyAudio Member
Join Date: Oct 2005

I suggest some pyrotechnics or firecrackers to make some sparks instead of connecting to electrical supply. Much safer.

  Reply With Quote
Old 9th January 2009, 06:18 PM   #6
SY is offline SY  United States
On Hiatus
SY's Avatar
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 2
"You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is."
  Reply With Quote
Old 9th January 2009, 08:42 PM   #7
diyAudio Member
Tom Bavis's Avatar
Join Date: Jun 2002
Location: Macedon NY
Aside from the EXTREME hazard, using a bridge rectifier directly from mains is just not practical, as both + and - sides of the bridge will be LIVE with respect to ground. Use an isolation transformer. If current is small, use a second 6.3V transformer in reverse from your 6.3V heater winding to give (isolated) mains voltage.
  Reply With Quote
Old 10th January 2009, 05:46 PM   #8
diyAudio Member
Join Date: Jun 2008
OK, thanks for the remarks. Consider me chastened.

Tom, clever idea on the filament transformers. I like that.
  Reply With Quote


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
Chassis Grounding Problem !! excetara2 Car Audio 6 28th September 2008 01:04 AM
chassis grounding question mnr102 Solid State 2 12th July 2008 09:14 AM
Grounding chassis borges Analog Line Level 1 16th March 2007 08:58 AM
Grounding SPDIF and Outputs to Chassis? mfrimu Digital Source 1 25th May 2004 07:05 AM
Grounding chassis Per Multi-Way 1 17th December 2002 10:21 PM

New To Site? Need Help?

All times are GMT. The time now is 06:39 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2