"DoN. Nichols" wrote:

On 2010-11-01, Michael A. Terrell wrote:

"DoN. Nichols" wrote:

Can you even buy carbon composition resistors any more? :-)


Yes:
http://www.mouser.com/Passive-Components/Resistors/_/N-5g9n?Keyword=carbon+comp&FS=True

Mouser has them mixed with their carbon film types on that page.

O.K. Ohmite I see -- not Allen Bradley. And the illustration
for the IRC ones looks strange. I guess it is a cutaway to show the
carbon core under the Bakelite. At least they have the Mil-STD
designation -- like

RC07GF184J

though they list those as 1/4 Watt, I seem to remember the RC20GF ones
were 1/4 Watt, RC42GF were 2 Watt, and (I think) RC32GF were 1 Watt.
And the RC07GF ones were 1/8 Watt. Perhaps they are using a more
heat-resistant potting than Bakelite on these, so they can bake them
smaller. :-)

Hmm ... they are ROHS compliant -- but the spec says that the
weight of lead present must be less than 0.10% -- which might allow for
lead tinned leads anyway. (Or were they lead tinned anyway? I remember
spot welding of resistor leads to nickel ribbon in cordwood construction
(and that such spot welding did not work well with a lead which had been
lead/tin solder coated, so perhaps they were coated with something other
than solder.

I still remember sending a "planner" (glorified stock clerk,
there) hunting for a RC20GF007J -- and when he started to doubt it,
showing him a RC42GF007J (hand painted :-), because he could read the
color codes to match the part number -- but did not know how to
translate that into resistance. :-) He spent a lot of a graveyard shift
on that -- with nobody else around to straighten him out. :-)


http://www.dannyg.com/examples/res2/resistor.htm


I wrote versions for 3 and 4 digit SMD resistors.


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