"Ken Finney" wrote in message
...

"Ed Price" wrote in message
news:mqdud.3291$Af.1453@fed1read07...

"Bill Turner" wrote in message
...
On Tue, 7 Dec 2004 18:12:35 -0500, " Uncle Peter"
wrote:

I wish I could find carbon comps (decent values) for two cents
each! Those days are long gone around these parts.

__________________________________________________ _______

The days of carbon composition resistors are gone for good reason.

Unless you are an antique collector and like to restore equipment using
original parts, use metal film resistors instead. Their stability and
reliability are far superior.

--
Bill W6WRT


I agree that carbon comp resistors have better alternatives if you are
looking for accuracy and stability and low noise. OTOH, carbon comp
resistors are an excellent choice for pulse generators and shaping
networks.
A metal film resistor will exhibit inductance and will often arc across
its
trim line, usually with catastrophic results. You can hit a 2-watt carbon
comp resistor with repetitive pulses of hundreds of watts (peak, keeping
the
duty cycle low) many times without significant resistance shift and
certainly without catastrophic failure.

The carbon comps are not the choice for all circuits, but they still have
their merits.


1. Something that has to be kept in mind is that most "carbon" resistors
being sold today are "carbon film", not "carbon composition" and
won't stand repetitive surge pulses.

2. IIRC, a mil-spec "10%" carbon comp can vary 42.4% over its
life and still meet spec. Expect commercial parts to be worse.

3. There are ceramic composition resistors available that have all
the good properties of carbon comp (except, I'm sure, cost) with
none of the bad properties.



The ideal resistors for abusive, high-speed transient applications are the
silicon carbide (ceramic) resistors (think Carborundum / Cesewid or whatever
they call themselves now). But the carbon comp resistors are much cheaper,
more versatile (lots more resistance values) and easier to use.

I don't know what you mean by the "life" of a carbon comp resistor. My
experience is that they last forever, until you kill them somehow. Drift,
under low power, hasn't been a problem for me. I have never seen 40% drifts,
except for very abused parts, and if you are using the 2-watt carbon comps,
you can hear or smell when you are abusing them.

The silicon carbide resistors can be pushed so hot that you can use them as
room heaters, industrial furnace elements or infrared sources. Oxidation of
the plated silver terminals is a small problem. Also, they do have a
temperature dependent coefficient of resistance (not as bad as incandescent
light bulbs).

I agree about the carbon film resistors; they blow up about the same as the
metal film resistors.

Ed
wb6wsn

Ed Price wrote:


I don't know what you mean by the "life" of a carbon comp resistor. My
experience is that they last forever, until you kill them somehow.
Drift, under low power, hasn't been a problem for me. I have never seen
40% drifts, except for very abused parts, and if you are using the
2-watt carbon comps, you can hear or smell when you are abusing them.

You apparently don't play with many old 30s-40s sets. Finding half the
high-value resistors only 200% out of whack would be a good day.

-BM

Ed Price wrote:


I don't know what you mean by the "life" of a carbon comp resistor. My
experience is that they last forever, until you kill them somehow.
Drift, under low power, hasn't been a problem for me. I have never seen
40% drifts, except for very abused parts, and if you are using the
2-watt carbon comps, you can hear or smell when you are abusing them.

You apparently don't play with many old 30s-40s sets. Finding half the
high-value resistors only 200% out of whack would be a good day.

-BM

Where the hell did this crap come from?? I never posted it, do I have a
virus?

Pete


" Uncle Peter" wrote in message
newsPAsd.803147$fY6.47606@fed1read06...
was intent on giving up documents only in
certain areas. In Watergate terminology, it was a "limited-
hangout" solution to the problem of controlling the damage.

Where the hell did this crap come from?? I never posted it, do I have a
virus?

Pete


" Uncle Peter" wrote in message
newsPAsd.803147$fY6.47606@fed1read06...
was intent on giving up documents only in
certain areas. In Watergate terminology, it was a "limited-
hangout" solution to the problem of controlling the damage.

" Uncle Peter" wrote in message
news:WtEud.12133$Ae.5187@fed1read05...
Where the hell did this crap come from?? I never posted it, do I have a
virus?


It's a spammer robot trying to flood news.admin.net-abuse.email
Don't reply to that newsgroup or you help the flood.

" Uncle Peter" wrote in message
news:WtEud.12133$Ae.5187@fed1read05...
Where the hell did this crap come from?? I never posted it, do I have a
virus?


It's a spammer robot trying to flood news.admin.net-abuse.email
Don't reply to that newsgroup or you help the flood.

" Uncle Peter" wrote in message
news:WtEud.12133$Ae.5187@fed1read05...
Where the hell did this crap come from?? I never posted it, do I
have a
virus?


Looks like the same computer that forged Randy & Sherry's ID at about
the same time.

Both seem to track back to Italy.

X-Trace: fata.cs.interbusiness.it 1102668495 4555 217.141.239.221 (10
Dec 2004 08:48:15 GMT)

X-Trace: fata.cs.interbusiness.it 1102668509 4555 217.141.239.221 (10
Dec 2004 08:48:29 GMT)

Virus on the Italian computer, or someone being a troublemaker, I'm
not sure.

jim menning

" Uncle Peter" wrote in message
news:WtEud.12133$Ae.5187@fed1read05...
Where the hell did this crap come from?? I never posted it, do I
have a
virus?


Looks like the same computer that forged Randy & Sherry's ID at about
the same time.

Both seem to track back to Italy.

X-Trace: fata.cs.interbusiness.it 1102668495 4555 217.141.239.221 (10
Dec 2004 08:48:15 GMT)

X-Trace: fata.cs.interbusiness.it 1102668509 4555 217.141.239.221 (10
Dec 2004 08:48:29 GMT)

Virus on the Italian computer, or someone being a troublemaker, I'm
not sure.

jim menning

a million monkeys or Jim Menning typed in news.admin.net-abuse.email:

snip

Virus on the Italian computer, or someone being a troublemaker, I'm
not sure.

Open port/unsecured box.

It's either a ****** called Dippy or Hipcrime or a dipclone thereof.
Basically the luser wants to disrupt nan-as by posting off-topic " sporgeries"
to other groups with a followup back here. Currently dippy has his knickers in
a twist since most folk here have advanced filtering or use services such as
supernews that quickly filter most of the crap.

I've found Hamster works well, you wind up running your own local news spool
though. And it's not the least trivial thing to get set up.

This is a good site to start reading about hamster and nfilter
http://web.ukonline.co.uk/davidgb/x_setup11.html

Have a happy,

--
rbg
Always remember that you are unique. Just like everybody else.
sig by KookieJar 6.3, got Kookie?