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Re: [Amps] Shorting Sticks

To: "AMPS" <amps@contesting.com>
Subject: Re: [Amps] Shorting Sticks
From: "Bill Coleman N2BC" <n2bc@stny.rr.com>
Date: Sun, 24 Apr 2005 16:52:56 -0400
List-post: <mailto:amps@contesting.com>
As one that has literally come across an open 225W bleeder.... I would never 
trust a resistor in series with the shorting stick.   If the caps are 
charged, something has already failed.  If the caps get damaged, too bad.  I 
would rather kill a few bucks worth of parts than me.

73, Bill  N2BC

PS:  It's a good idea to routinely test the shorting stick too.


----- Original Message ----- 
From: "Will Matney" <craxd1@ezwv.com>
To: <amps@contesting.com>
Sent: Sunday, April 24, 2005 4:20 PM
Subject: Re: [Amps] Shorting Sticks


John,

Your saying that a dead-short, quick discharge of a capacitor bank wont be 
rough on the capacitors?

I think everyone knows it to discharge them for safety, but why take a chace 
on the capacitors being damaged on top of it? I can wait 2-3 seconds before 
I do any work, and that's about all it takes. Henry spoke of that Gates 
supply, and I'll about bet they woundn't take a chance on those capacitors 
shorting them to ground, and that being they do use a resistor bank for the 
purpose. Especially over the cost of the capacitors. I think one can still 
be safe and not cost them extra in parts.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 4/24/05 at 12:36 PM John Irwin wrote:

>I THINK YOU DUDES ARE MISSING THE FOREST>>>>>>>>>>>
>
>The purpose of the SHORTING STICK is to KILL THE HIGH VOLTAGE INSTEAD OF
>YOU!
>
>The shorting stick will only damage something is it has already failed or
>left been left on
>                                              BY ACCIDENT.
>
>ie  A bleeder that goes open with no warning.  a plate supply powered ,and
>you forgot to turn it off etc......It protects you.  so what if something
>dies on the power supply>>>  You didn't<<
>You also don't want any other resistors,bleeders,relays or any other junk
>connected to the shorting stick.  just a hook ,10 gage wire and a
>alligator clip to ground,  stick should be about a foot and a half long.
>
>The habit of hooking the shorting stick on the hv line may save your
>relatives pain,and your life,but only if you do it as practice each and
>every time!  First thing done.  Last thing removed
>
>john kb9tc
>
>
>
>
>Will Matney <craxd1@ezwv.com> wrote:
>Perzactly! My reasoning on the discharger was to allow the caps to
>discharge through some resistance at first to limit the current, and after
>a short time, say 2 seconds, a dead short by a relay would finish it off.
>To me, the quick discharge of a capacitor is really hard on it and can
>ruining the dialectric.
>
>Another thing I dont trust are those safety latches on most amps which
>mostly short the caps to ground if the lid is opened. Lets say the contact
>was made once under a full charge, or worse, while the amp was running.
>Then an arc would burn the contact surface maybe to a complete open. This
>then could make a high resistance there or even make it fail in the future
>to where it wouldn't discharge them at all. Next, some poor un-assuming
>soul went ahead and put his hands on a fully charged capacitor bank
>(providing the resistors was bad).
>
>One rule I always do on a charged capacitor bank or a running amp is to
>keep one hand behind my back and use the other to do any measurements.
>This way if I slip, the worse case would be to just get it maybe from a
>finger to the wrist, across the fingers, etc., and not through my body.
>Just that shock to the hand is enough to knock the dickens outta ya really
>quick! One trough the body though could stop your heart! I've been bit
>before it it sure aint no fun.......
>
>Best,
>
>Will
>
>*********** REPLY SEPARATOR ***********
>
>On 4/24/05 at 10:20 AM R@contesting.com;Measures wrote:
>
>>A 0½ (zero-ohm) shorting stick can damage an amplifier since there is
>>virtually nothing to limit peak discharge current. If a 1000-ohm or
>>so, 100 to 225 watt resistor is added in series with the shorting stick
>>to limit current, there is less chance of damage.
>>
>>
>>Rich Measures, 805.386.3734, AG6K, www.somis.org
>>
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>
>
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