Quick question about grounding - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

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
Reply
 
Thread Tools Search this Thread
Old 3rd February 2013, 05:31 PM   #1
surfstu is offline surfstu  United Kingdom
diyAudio Member
 
Join Date: Nov 2008
Location: London
Default Quick question about grounding

I bring earth into amp through iec socket and go straight to chassis with it for ground...

My HT secondary winding has center tap and this goes to chassis through 500mA fuse

the heater windings have no CT.

One of the 6.3Vac heaters supplies goes to heaters but I am also placing a bridge rectifier in the circuit and referencing the positive of this to Ground and therefore getting -7V for a ccs that i need.

The OV for the B+ is referenced from ground....

Does this sound correct?

Thanks in advance - Stuart
  Reply With Quote
Old 3rd February 2013, 06:45 PM   #2
surfstu is offline surfstu  United Kingdom
diyAudio Member
 
Join Date: Nov 2008
Location: London
what I'd really like to know:

can you force one end of a heater winding to be ground?
  Reply With Quote
Old 3rd February 2013, 07:53 PM   #3
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
My HT secondary winding has center tap and this goes to chassis through 500mA fuse

The center tap to ground is fused?
__________________
Kevin
  Reply With Quote
Old 3rd February 2013, 07:59 PM   #4
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Quote:
Originally Posted by surfstu View Post
what I'd really like to know: can you force one end of a heater winding to be ground?
Heater/filament windings are often grounded on one end or through the center tap if available. Referencing the heater to ground is done to reduce hum problems were they to exist. You can do what you propose as long as the heater wiring is not grounded at any other point you are not aware of. Of course you will need some filtering for this negative voltage source.
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 3rd February 2013, 08:11 PM   #5
N4BBQ is offline N4BBQ  United States
diyAudio Member
 
N4BBQ's Avatar
 
Join Date: Nov 2009
Location: Dahlonega, GA
Why fuse the center tap other than a false sense of security and if your current power transformer doesn't have a tap, I'd add a small separate transformer to power the CCS you need and leave the filament alone.
  Reply With Quote
Old 3rd February 2013, 08:55 PM   #6
surfstu is offline surfstu  United Kingdom
diyAudio Member
 
Join Date: Nov 2008
Location: London
@N4BBQ - I was going to fuse the center tap simply because the original circuit from where i took the transformer from had a fuse here... I was just going to copy the gz34 circuit but add my own filterting section that I've established from PSUD2 - if you guys have a better idea then I am all ears as I am still wrestling with my noob status..

@hollowstate ... thankyou, I figured I could do this - the heaters are not connected to ground anywhere else as this is a build from scratch. I think I am clear now - My 0V is always connected to the chassis for ground although I've heard it is wise to still run the 0V through the amp on its own wire and drop to ground after each section?

The transformer has 2 6.3Vac supplies and a 5Vac for the gz34

I have used one 6.3Vac for vu meters and the rermaining 6.3Vac will supply 4 ecl86 heaters in parallel but before it reaches them there will be a bridge across it with the positive connected to 0V bus and negative to supply my -7V ccs (3mA)

Thanks for everyones input, I just thought that putting a CT from main secondary to the same bus as an anode side of one of the 6.3Vac might be stupid, but obviously not...

Stuart
  Reply With Quote
Old 3rd February 2013, 08:57 PM   #7
surfstu is offline surfstu  United Kingdom
diyAudio Member
 
Join Date: Nov 2008
Location: London
N4BBQ - have attached original circuit where the transformer was taken from... maybe I do not need the 500mA fuse?

Just a fuse on the AC inlet?

stuart
Attached Images
File Type: jpg s99 PSU.jpg (165.9 KB, 155 views)
  Reply With Quote
Old 3rd February 2013, 09:07 PM   #8
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Stuart,
Assuming that one 6 volt winding is for the VU meter (lamps only?), why not use that 6 volts for the rectified negative source. The circuit would probably perform better hum wise with the heaters referenced directly to ground. The bridge gives you only cycle to ground.
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 3rd February 2013, 09:21 PM   #9
surfstu is offline surfstu  United Kingdom
diyAudio Member
 
Join Date: Nov 2008
Location: London
Thanks hollowstate...

well, I'm just working from a suggestion from the guy who drew the schematic for the ecl86 huey I'm building so I thought I would go with his option, I just wasn't sure about putting it on the same 0V bus as the rectified B+

You've cleared it up for me i think so cheers
Attached Images
File Type: jpg heater_ccs_mk2.jpg (21.1 KB, 151 views)
  Reply With Quote
Old 3rd February 2013, 11:44 PM   #10
12E1 is offline 12E1  United Kingdom
diyAudio Member
 
12E1's Avatar
 
Join Date: May 2012
Location: Near Huntingdon, Cambridgeshire, UK
Quote:
Originally Posted by surfstu View Post
N4BBQ - have attached original circuit where the transformer was taken from... maybe I do not need the 500mA fuse?

Just a fuse on the AC inlet?

stuart
Fusing the secondary is a good thing. However, a fuse in the centre tap only protects against some types of fault such as excessive DC current taken from the rectifier. It would not protect the transformer if the rectifier valve or wiring developed a short between the two anode voltages. I would put a fuse in each AC line to the rectifier, and no fuse in the centre tap connection to ground. That way you are providing greater protection for the transformer.
  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
Quick guide on Grounding OnAudio Solid State 46 12th December 2012 05:43 PM
Quick question on grounding procedure ZLyzen Power Supplies 2 28th July 2012 09:36 AM
quick grounding question gain Power Supplies 7 22nd October 2008 03:19 PM
Quick question about star grounding jn2630 Tubes / Valves 8 21st January 2008 01:31 AM
A quick (haha, no really) grounding question geaugafletcher Chip Amps 2 22nd December 2006 02:53 PM


New To Site? Need Help?

All times are GMT. The time now is 08:20 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