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At 05:37 PM 1/1/02 -0500, you wrote:
> > I found a dummy load construction project in the '92 ARRL Handbook.
> > It calls for a "Carborundum Resistor, P/N 889SP500k".
Tom, W8JI wrote:
>Whatever you do, just be sure the resistor is designed to be
>submerged in oil. Some resistors are not coated, and gradually
>soak up oil causing resistance to increase over time.
HNY All,
Tom's caution is quite correct, so be advised. You will note that the P/N
above contains the designator "SP" and this is the proper one for
oil. The "AS" type is the one to avoid for oil, or other liquid
immersion. The composition of the two is totally different. I tried
conformally coating the AS type and it still became a sponge, no doubt due
to the fact that the inside of the tube was not coated well enough and the
end contact areas remain a problem.
73,
Marv, W6FR
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<html>
<font size=3>At 05:37 PM 1/1/02 -0500, you wrote:<br><br>
<blockquote type=cite class=cite cite>> I found a dummy load
construction project in the '92 ARRL Handbook. <br>
> It calls for a "Carborundum Resistor, P/N
889<u>SP</u>500k".</font></blockquote><br>
Tom, W8JI wrote:<br><br>
<blockquote type=cite class=cite cite><font size=3>Whatever you do, just
be sure the resistor is designed to be <br>
submerged in oil. Some resistors are not coated, and gradually <br>
soak up oil causing resistance to increase over
time.</blockquote><br>
HNY All, <br><br>
Tom's caution is quite correct, so be advised. You will note that
the P/N above contains the designator "SP" and this is the
proper one for oil. The "AS" type is the one to
avoid for oil, or other liquid immersion. The composition of the
two is totally different. I tried conformally coating the AS type
and it still became a sponge, no doubt due to the fact that the <i>inside
</i>of the tube was not coated well enough and the end contact areas
remain a problem. <br><br>
73,<br><br>
Marv, W6FR</font></html>
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