ASC metal can polypro caps: ground the metal can to AC ground? - 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 5th September 2006, 04:13 AM   #1
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
Default ASC metal can polypro caps: ground the metal can to AC ground?

your thoughts?

thanks for the help
  Reply With Quote
Old 5th September 2006, 04:55 AM   #2
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Yes, if they are outside the chassis where they can be touched.
  Reply With Quote
Old 5th September 2006, 06:13 AM   #3
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
Quote:
Originally posted by dsavitsk
Yes, if they are outside the chassis where they can be touched.

but not all metal that can be touch are grounded. say a metal knob for a volume control?
  Reply With Quote
Old 5th September 2006, 09:04 AM   #4
CLS is offline CLS  Taiwan
diyAudio Member
 
Join Date: Jun 2005
Location: Taiwan
I don't know ASC metal can, but I'd been shocked by some unshielded aluminum tops of electrolyte caps.

Ouch!

Those caps were originally fixed onto metal chassis directly by nylon cable ties. After I was shocked, I cut those cable ties & put some more thich cardboard between caps & sheet metal, then re-fixed them. As the thin heat-shrink film seems vulnerable.
  Reply With Quote
Old 5th September 2006, 11:43 AM   #5
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
Quote:
but not all metal that can be touch are grounded. say a metal knob for a volume control?
True, but ungrounded, touchable, conductive elements are only dangerous when high voltage carrying wire gets loose and makes contact with the element. There's usually no high voltage around the volume control...

Simon
  Reply With Quote
Old 5th September 2006, 06:08 PM   #6
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
A metal knob on a volume control is connected with the shaft, which has a sliding contact with the case, which is mounted to the metal chassis... so it IS grounded. If the pot's case ISN'T grounded, expect hum problems...
  Reply With Quote
Old 5th September 2006, 07:37 PM   #7
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
One general caveat I recently discovered, grounding a metal-bodied signal cap should be considered carefully. A coupling position isn't likely with an ASC but it's common with Russian Telfons, K40Y-9 PIOs and Russian silver mica. A Fluke DVM measured a whopping 70pf between either terminal and exterior case on the latter. That equated to (a probably not very linear) 70pf shunting the driver to ground in my amp. Even though it measured flat floating the cap body still cleaned up the sound significantly.
  Reply With Quote
Old 5th September 2006, 10:31 PM   #8
jarthel is offline jarthel  Australia
diyAudio Member
 
Join Date: Jan 2002
Location: somewhere in Australia
so the good idea is to ground it to AC?
  Reply With Quote
Old 6th September 2006, 01:34 AM   #9
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
If the cap is inaccessible to the user, leave it floating, and keep low level signal leads away from it. If anyone can touch it GROUND IT. The can will often collect enough electrons to zap you. If it internally shorts, it can kill you.

Connecting the can to an AC ground will still put the previously mentioned 70pF to ground.

I have received the same unwanted experience from some Panasonic electrolytics. The big ones have a plastic cover over the can. The 100uF 350 volt ones do not, and the can will shock you.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 6th September 2006, 02:50 AM   #10
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
Hi tubelab. In situations where the cap is in the signal path and the capacitance to ground a detriment, what do you think about using a bleed resistor? 70 pf in series with half a meg might be fine.
  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
Should I directly connect my signal ground to chassis ground? Bricolo Solid State 4 18th March 2014 09:42 PM
Parallel LM3886, input ground, power ground, safety resistor and oscillations. markiemrboo Chip Amps 5 9th August 2007 03:50 PM
Metal dome should always go with metal cone? Is this a rule? Jay_WJ Multi-Way 5 5th February 2007 06:53 PM
Metal Oxide vs flamme proof vs metal film ostie01 Parts 28 26th June 2006 06:38 AM
does connecting mains ground with circuit ground create a ground loop? jarthel Everything Else 0 25th June 2003 12:55 PM


New To Site? Need Help?

All times are GMT. The time now is 06:41 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