Safety Practices, General and Ultra-High Voltage - Page 12 - 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 20th March 2007, 10:52 AM   #111
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Last question first: yes. Power supply components especially have been known to cause zaps to the unwary. If you're new to electrical work, do NOT play around inside a tube amp without experienced supervision even if the power is off. (Reality check: if the amp is powered down for some time, ranging from minutes to a day or so, anything really dangerous will have discharged)

First question: your amp will be FAR safer if you use an isolation transformer and a three-wire line cord with the green lead bolted securely to the chassis. Nothing in this world is perfectly safe, but those two precautions will make your amp as safe as it can be.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 20th March 2007, 11:05 AM   #112
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default Rather sad

Quote:
Originally posted by gmphadte
A bird sitting on an overhead line is safe if it does not touch the second line.
Not if that overhead wire happens to be one wire of an open RF transmission line feeding a short wave transmitting aerial. Apparently, their legs get cooked, and although they can fly away from the feeder, they can't take off when they land on the ground and flutter about helplessly until they die.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 21st March 2007, 12:37 AM   #113
diyAudio Member
 
frank754's Avatar
 
Join Date: Jan 2007
On the power supply end, even if the above precautions are taken, you can run a 1 megohm resistor across the filter capactitors, and it should bleed them of any charge after several minutes.
  Reply With Quote
Old 21st March 2007, 05:07 AM   #114
diyAudio Member
 
Join Date: Jul 2003
Location: Dona paula, Goa
Quote:
Originally posted by EC8010
Not if that overhead wire happens to be one wire of an open RF transmission line feeding a short wave transmitting aerial. Apparently, their legs get cooked, and although they can fly away from the feeder, they can't take off when they land on the ground and flutter about helplessly until they die.
Good info,
But the birds don't DIY, if I am not wrong LOL

Gajanan Phadte
  Reply With Quote
Old 27th March 2007, 09:10 PM   #115
diyAudio Member
 
richwalters's Avatar
 
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
What we are trying to get over is NEVER TO PUT BOTH HANDS ON DIFFERENT PARTS OF a chassis which has dangerous potentials in it OR with probes which could complete a body circuit. I live alone and regulary tamper with 550V upwards but I discipline myself always keep the other hand away from the action. One thing at a time and use a probe with a claw to complete the other side of a circuit.

richj
  Reply With Quote
Old 28th March 2007, 01:18 AM   #116
diyAudio Member
 
Join Date: Mar 2007
Send a message via AIM to daboyter
the whole keep one hand out thing seems like a good idean, but is it not possible to complete the circuit with another body part like your feet if they are touching something?
  Reply With Quote
Old 7th April 2007, 11:08 PM   #117
VivaVee is offline VivaVee  New Zealand
diyAudio Member
 
Join Date: Jun 2004
Location: Auckland, NZ
Yes, it is possible to complete the circuit using your feet. This is why we used to stand on a pile of DRY newspapers as a make shift insulator when working on live switchboards.

A few points to add to the previous discussions:

1/. Wear rubber shoes and use an dry insulated floor covering
2/. Use insuated crocodile clips on ALL multimeter leads
3/. Use insulated clips on your power supply bleeder resistor leads
4/. Don't use ESD wrist straps ...

Regarding the GFI (called ELCB or earth leakage circuit breakers down here) and isolation transformer discussion

1/. Do get an electrician to install a suitable sized GFI/ELCB in the switchboard that supplies mains power to your workshop area
AND
2/. Do use an isolation transformer on the work area itself - suitably installed in an insulated enclosure with a suitable mains socket on the front

My lab area is supplied by a dedicated mains feed that has a medical rating 32A ELCB in the line. The medical rating means that the ELCB trips at 10mA fault current rather that the usual 30mA fault current. This feeds ALL power sockets in the lab. There is a big red kill switch VERY handy to the workbench that allows me to kill ALL power to the bench instantly. On the bench, in a wooden enclosure is a 2kVA isolation transformer that feeds a 5kVA variac. This has both current and volt meters on the front panel. This allows me to slowly power up mains circuits and monitor load ( and sometimes fault) current as the output mains voltage slowly rises to 230V. I can also increase the mains outlet voltage up to 260V to test potential fault conditions, but that is another story.

Next to the bench is a rack of leads that includes the aformentioned power supply bleeder resistor. The usual one is 470 ohms 25W ( one of those big aluminium housed beasties ). The leads have large insulated clips (dseigned for charging car batteries but very useful in this instance)

Now all of the above is what you HAVE to do when working on high/mains voltages and circuits. But, the game changes when working on low voltage static sensitive micropressor circuits. If, like me, you work on both, then you have to conciously shift a mental gear as you move from one to the other.

But your default mode has to be safe with the stuff that kills you.

You may kill the odd microprocessor with ESD but your partner, children and friends will thank you. Dead micros are cheap ... and you can buy another one easily enough.
__________________
Alan
Hope is not a reliable design discipline
  Reply With Quote
Old 9th April 2007, 02:01 AM   #118
Tweeker is offline Tweeker  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Cincinnati, Ohio
At VOA Bethany the birds what got too close to the line would explode and strike a 250kW Spanish speaking arc.

Click the image to open in full size.
__________________
Be sure your foil hat has a good low impedance ground.
  Reply With Quote
Old 9th April 2007, 04:20 PM   #119
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Quote:
Originally posted by Tweeker
At VOA Bethany the birds what got too close to the line would explode and strike a 250kW Spanish speaking arc.
I know it's cruel to laugh at such an image, so I won't.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 9th April 2007, 05:03 PM   #120
Tweeker is offline Tweeker  United States
diyAudio Member
 
Join Date: Dec 2004
Location: Cincinnati, Ohio
Its not nearly so horrible as what you described.

The majority of power outs in fair weather are caused by squirrels. A business a friend of mine works lost time and had to spend $12,000 replacing a medium voltage fuse because of one.
__________________
Be sure your foil hat has a good low impedance ground.
  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
Workbench safety practices? Stormrider Equipment & Tools 3 3rd August 2008 05:08 PM
Safety with high volts: 101 rick57 Tubes / Valves 34 1st April 2005 04:51 PM
Safety Practices, General and Ultra-High Voltage DrDeville Everything Else 49 23rd September 2004 09:31 AM


New To Site? Need Help?

All times are GMT. The time now is 07:17 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