RE: FILT1.JPG (Was Terry's NST Filter Network)

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Gary,

The file FILT1.jpg was out of date and has been removed.  See:

http://users.better-dot-org/tfritz/NSTFilt.jpg

I presently use Digi-Key L100J1K0-ND resistors as described at:

http://www.digikey-dot-com/EC/V3/387.pdf

They are Ohmite 100 Watt 6.5 x 0.75 inch vitreous enamel fixed value power
resistors.  

They have no aluminum heat sinks but are just wire wound on a ceramic core
under ceramic glazing.  They should easily stand continuous 20+ kV spikes
across their terminals...

'Dale' makes similar rated resistors with the gold anodized aluminum heat
sinks around them.  At work, they blow out like little shotguns...  I have
a dent in my polycarb S-glasses from one of them turkeys...  Very poor for
high voltage (any voltage!) especially when Dale screws up and does not
center the elements in the silicon potting.  Dropping 480V three phase
across one when the internal element is lying against the aluminum case...
Grrrrr!   

But "I" don't use them...  Those Ohmite ceramics are the best out there IMHO.

Cheers,

	Terry



At 10:06 PM 6/5/00 -0400, you wrote:
>I think you will have a problem using the resistors that you described.  The
>resistors in the filter network will develop 10's of kV across them.  The
>aluminum heat sink on your resistors will reduce the maximum voltage the
>resistor can withstand, and you will get arcing from the leads to the case.
>You have to use air-cooled ceramic resistors.
>
>Regards, Gary Lau
>Waltham, MA USA
>
>
>>Original Poster: "Daniele Bortoluzzi" <dbortoluzzi-at-sogeda.it> 
>>
>>Tnx Terry and Paul for all the infos,
>>I will go for the newer design :)
>>
>>Instead of doorknobs I am gonna use series of 6Kv ceramic caps,
>>am I going right ? I will use 2 25W resistors of that type with
>>the heat sink (they are like gold plated)
><snip>
>