[AMRadio] ground sticks again


david knepper collinsradio at adelphia.net
Mon Jun 5 10:11:54 EDT 2006


If I could add my "two cents" to this discussion.  Any ham who has the 
slightest thought that a large oil filled capacitor is charged should bleed 
the voltage to ground through a 100K  resistor, acting as a bleeder 
resistor.

By the way, be very careful not to assume that your bleeder resistor is 
functional.  Lots of folks, including myself, got nipped by a bleeder that 
opened up!  Thank goodness it was only a few hundred volts but what if ....

A shorting stick should be in evey hamshack.  The one that I have is made 
from a phenolic rod about a foot long with a insulated copper braid with a 
clip attached to a hook rod at one end that I drape over the filter 
capacitors when working on the amplifier.  It was issued to me when I was in 
the Air Force working on 5 KW transmitters.  If the sergeant saw you without 
your "Jesus stick" you might get your butt kicked.

Crazy story:  I had a friend who used to charge up a 100 mfd/4000 volt oil 
filled capacitor to see how long it would stay charged!!  He wasn't too 
bright.


Dave, W3ST
Publisher of the Collins Journal
Secretary to the Collins Radio Association
www.collinsra.com - the CRA Website
Now with PayPal
CRA Nets: 3805 Khz every Monday at 8 PM EST
and 14255 every Saturday at 12 Noon EST
----- Original Message ----- 
From: <W4AWM at aol.com>
To: <amradio at mailman.qth.net>
Sent: Monday, June 05, 2006 9:42 AM
Subject: Re: [AMRadio] ground sticks again


> In a message dated 6/5/2006 0:25:48 AM Eastern Daylight Time,
> k4kyv at hotmail.com writes:
>
>> it can ruin the capacitors with excessive
>> instantaneous current surges.  Better to first discharge through a
>> resistance to limit the discharging current, then apply the "coup de 
>> grace"
>> by shorting  directly.
>>
>
> How do you intend to handle the resistor while doing the discharging? You 
> are
> still going to need a shorting stick. If the initial charge opens the
> resistor, tyou are still going to have a huge discharge when tou roun the 
> cap
> directly.  It is much better to take the slight chance of discharging the 
> cap the
> direct way than messing around with some Rube Goldberg resistor 
> arrangement. If
> the Great Electron Gods had intended for capacitors to be discharged 
> through a
> resistor (other than a bleeder) before working on a circuit, them he would
> have made discharge sticks with built in resistors. I have never seen one, 
> have
> you?
>
> Transmitting caps are not that hard to find, not that expensive.  You can
> find them at nearly every hamfest. At the Manassas, VA hamfest yesterday, 
> there
> were 2 large piles of them at one vendor in the flea market and he would 
> almost
> pay you to take them home.
>
> 73,
>
> John,  W4AWM
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