[Amps] Shorting Sticks

[R@contesting.com]

On Apr 24, 2005, at 6:28 PM, Bill Coleman N2BC wrote:

> I'm not sure what resistor you are referring to Rich.

The R in the stick.  Perhaps it should be called a discharger-stick to 
more accurately describe what it does.
>
> In the power supply that bit me there were two 100K 225W resistors in 
> series across 4KV and one was open - no arcing.  Examination of the 
> open resistor showed only a hairline crack a couple inches from one 
> end.
>
> If you mean the current limiter you propose in a shorting stick, would 
> you trust it to arc so you knew it was open?

According to my DMM, the 1k-ohm, 100w R in my discharger-stick has 
never opened. My guess is that even if it did, it would not read 
infinite R.

> I'll go for the big bang of a heavy hunk of wire right to ground.  
> Safety glasses on, one hand in my pocket.
>
>
> Someone mentioned watching the HV meter.  In the case I had,  the HV 
> meter indicated zero - that's the bug I thought I had.  The metering 
> was done across a  small (10K ?) 25W resistor which was at the bottom 
> of the open bleeder.  Never trust the meter!

And so, do not take the $hortcut of using a WW bleeder for the 
voltmeter multiplier.  However, even if one accidentally touched a 25uF 
cap charged to 4kV, would it do more damage than making a hole in one 
finger?  I know of no case where anyone has been killed by such.
>
> 73, Bill   N2BC
>
> ----- Original Message ----- From: "R. Measures" <r at somis.org>
> To: "Bill Coleman N2BC" <n2bc at stny.rr.com>
> Cc: "AMPS" <amps at contesting.com>
> Sent: Sunday, April 24, 2005 8:40 PM
> Subject: Re: [Amps] Shorting Sticks
>
>
>
> On Apr 24, 2005, at 2:26 PM, Bill Coleman N2BC wrote:
>
>> It won't get warm at all if it's open...
>
> What will prevent the open from arcing?
>>
>>
>> ----- Original Message ----- From: "R; Measures" <r at somis.org>
>> To: "Bill Coleman N2BC" <n2bc at stny.rr.com>
>> Sent: Sunday, April 24, 2005 5:18 PM
>> Subject: Re: [Amps] Shorting Sticks
>>
>>
>> A typical value for a current limiter resistor in a shorting stick is
>> 400 - 1000-ohms, 100w.  Discharging even 200J barely gets a 100w
>> resistor warm.
>>
>> On Apr 24, 2005, at 1:52 PM, Bill Coleman N2BC wrote:
>>
>>> 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.
>>
>> Agreed, but if the I-limiter resistor is open, there would be a
>> considerable fireworks show.
>>>
> snip
>
>
>



Rich Measures, 805.386.3734, AG6K, www.somis.org