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Windows 7: Teen electrocuted while working on unplugged computer

10 Oct 2012   #31
gregrocker

 

Thanks. Is it true that a blown capaitor in a Plasma TV may appear as such, like bulging capitors in mobos? Is it then worth replacing the capacitor on a 5 year old Plasma TV providing adequate and tested discharge is done of the entire power supply?

The TV is already replaced so it's only a tech project..


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10 Oct 2012   #32
sygnus21

Windows 10 Pro
 
 

Quote   Quote: Originally Posted by gregrocker View Post
This thread may literally be a lifesaver because I was soon going to take apart my Uncle's big screen plasma TV to see if I can spot capacitor damage after it (possibly) fried during power surge. I have a video showing how to do this but with nothing said about discharging residual current. Will a voltage tester suffice held on the leads of a capacitor which appears to need replacement?
This method gets the job done, and is one I used: How to check for high voltage and discharge - YouTube

Quote   Quote: Originally Posted by gregrocker View Post
Thanks. Is it true that a blown capaitor in a Plasma TV may appear as such, like bulging capitors in mobos? Is it then worth replacing the capacitor on a 5 year old Plasma TV providing adequate and tested discharge is done of the entire power supply?
For the most part yeah. But it depends on difficulty, price, and skill. I've replaced two capacitors in my TV. The capacitors cost about 10 bucks a piece, but the task took about 4 hours due to the difficulty of getting to the part(s).
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10 Oct 2012   #33
brianzion

Operating System : Windows 7 Home Premium Edition 6.01.7600 SP1 (x64)
 
 

Quote   Quote: Originally Posted by Dwarf View Post
Discharging a capacitor involves placing a load across its terminals so that the stored energy is dissipated safely. The load is typically a wirewound power resistor, although a mains light bulb can also be used. If a voltmeter is connected in parallel, you can also see the residual voltage reduce until it is close to zero (although it will probably never actually be exactly zero).

A word of warning: Never touch the terminals of the capacitor directly, and also be aware that any residual power left in any other capacitors could potentially recharge the capacitor you have discharged. Ideally, you need to isolate one of the capacitor terminals from the rest of the circuitry to prevent this from happening. Above all, never try to discharge a capacitor by merely shorting its terminals, as this can lead to the capacitor rapidly overheating, with the resultant possibility of it exploding or even catching fire (or both).
good sound advice the tool we used had clips on for the terminals to be connected to a large box with a special device inside to take the charge everything was heavily insulated i cant remember what it was called.
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10 Oct 2012   #34
Zepher

Windows 7 Ultimate 64bit
 
 

Quote   Quote: Originally Posted by gregrocker View Post
Does holding the power button for x seconds actually discharge the residual power in the capacitors or is that for something else?

Yesterday my nephew was swapping in a new PSU for my Dad's desktop which was left only with a blinking green LED on back of PSU. He reported that when he plugged up the new PSU it had a solid green. Does this LED show residual power, or just power on?
That just shows the status of the psu, no led or blinking led means a fault in the output if the psu.

I've got to change 2 capacitors in my left Alesis M1 Active MK2 speaker. This 2 caps sit right next to a heat sink and dry up faster from the extra heat over time. Took 10 years for this one. I already replaced them on the right speaker about 6 months ago.
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10 Oct 2012   #35
NoN

Windows 7 Professional SP1 - x64 [Non-UEFI Boot]
 
 

Quote   Quote: Originally Posted by gregrocker View Post
Does holding the power button for x seconds actually discharge the residual power in the capacitors or is that for something else?

Yesterday my nephew was swapping in a new PSU for my Dad's desktop which was left only with a blinking green LED on back of PSU. He reported that when he plugged up the new PSU it had a solid green. Does this LED show residual power, or just power on?

Poor guy...

That's what i thought when holding power button to discharge statics, but no!!!

I've tested it against my will while cleaning a little my computer.

The green light was off and i was pretty sure nothing could happen, but while vacuuming with low air pressure inside i certainly made a little static and the green led power on for few seconds.

The card is protect by low emi and surge....so that was nothing to damage the components, but I understood i'd better not do that again for the components and for me either.

Now i perfectly know that even all unplug that damn psu holding charge.
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10 Oct 2012   #36
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by Dwarf View Post
Discharging a capacitor involves placing a load across its terminals so that the stored energy is dissipated safely. The load is typically a wirewound power resistor, although a mains light bulb can also be used. If a voltmeter is connected in parallel, you can also see the residual voltage reduce until it is close to zero (although it will probably never actually be exactly zero).
Great advice. I'm an EE and anyone can become complacent. I remember as a young eng technicians watching my moves when working in the power supply industry.

Maybe a safety sticky under hardware Brink?
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11 Oct 2012   #37
galaxys

Windows 7 Home Premium 64bit SP1
 
 

Bummer. Also be careful of moisture or spilled drinks around cords/plugs.
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19 Oct 2012   #38
JimJoe

Vista Home Premium, contemplating moving to Linux
 
 

My first electronic training was on large vacuum tube/valve radars. High voltage and high amperage. I have noticed the safety around power taught us in that situation has never been mentioned in any computer class I have taken.

My condolences to his family and friends.
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19 Oct 2012   #39
legacy7955

win 7 home premium 64 bit
 
 

A real tragedy....So unfortunate and preventable as well. My condolences to the family of this aspiring "geek".

I think the reason that the possibility of electrocution from a computer is not often thought of is that past the power supply itself (in current computers) the voltages are very low and will not do serious harm. But the power supply of every PC until present can be lethal if not handled carefully. While the line voltage is also deadly the juice from those big caps can and is just as deadly.

I agree with others that unless you are properly trained in AC/high voltage DC electronics NEVER open or carelessly handle the power supply!

Thanks for posting this Brink, I think you brought attention to something that is very overlooked in the PC world.


PLEASE BE CAREFUL !
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20 Oct 2012   #40
ICIT2LOL

Desk1 7 Home Prem / Desk2 10 Pro / Main lap Asus ROG 10 Pro 2 laptop Toshiba 7 Pro Asus P2520 7 & 10
 
 

Well from my point of view the report was rather callous insomuch that as someone has already said as teens we are invincible and hey we knew it all back then. It certainly didn't show much compassion but hey what is that today when human life is so cheap GGRRRRR!!

Myself would hazard (no pun) a guess that this unlucky kid touched a really fully charged cap or even if it were not fully charged enough to upset his heart rhythm. He may have also had some congenital heart defect too that exacerbated the problem whereby the shock was enough to stop his heart.

In case anyone is interested this is the mechanics behind those defib machines one sees on those TV shows where the "dead" person is given a jolt to restart the heart. When in actual fact hat jolt actually stops the heart in the hope that some regular sinus rhythm will kick in from the hearts own pacemaker and then again hopefully by the cardiac centre within the brain stem. That shock is delivered by no less than some rather large caps which you can hear charging when getting ready to do the procdure.

In this unfortunate incident it did just that by the sounds of things and I feel sincerely for those poor family of that young fellow. Thinking back it could have been me and you wouldn't have my company right now like a few others I guess who frequent this forum .

If nothing else a timely reminder of what we are dealing with sometimes I feel rather blithely.
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 Teen electrocuted while working on unplugged computer




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