Thanks to David, Don and Gary for making me feel better this morning
about my resistors.
I have been testing each prior to installation but when came to that
group, got lazy and decided to only check them AFTER
installation...which then made me wish I hadn't gotten lazy!!! Great
object lesson here...don't take shortcuts!
It just didn't seem possible that measuring on the leads directly on
either side of the component that there would be that much
resistance draw after mounting...but the fact that it was so uniform
on both of them, plus the third one (68 ohm) being down that much as
well made me curious! I really appreciate the explanations...that's
why I joined this reflector and am assembling the K2..to learn!
I'm already dreading the empty feeling that will come about when it's
done and I don't have it to retreat to in the evenings! But, I've got
the SSB board setting in a box to assemble, and keep pouring over the
options on the website, so as long as the XYL doesn't completely pull
the purse strings shut, I'll be able to keep on building!
Thanks.
Quoting "David F. Reed" <[EMAIL PROTECTED]>:
David,
I am not sure how best to put this...
Imagine you put a resistor of infinite value in parallel with your 100
ohm resistor and measured it at the ends of the 100 ohm resistor; of
course, you would see the 100 ohms; what if the two resistors were 100
ohms each? well, being in parallel, you would see 50 ohms; if you put a
0 ohm resistor in parallel with the 100 ohm, what would you see?
so anything with some resistance to it, a resistor, a trace, a relay
coil, will affect the resistance you measure.
A nice mental exercise you can do with a handful of resistors is to
tack solder them together into a cube, and start measuring across
different points; maybe even make it simple, and do just a square first
(4 resistors); you might start to develop some intuition about how this
works. try it with same value resistors first...
I think you will find your resistors are fine; when you get to a test
sequence in the manual, you will see they tell you what to look for in
resistance that is quite different and that this intuition gained will
help you feel more comfortable.
Alternatively, if you are more accustomed to math, you might just learn
some of the associated applications of Ohm's law, or do both what the
heck...
[EMAIL PROTECTED] wrote:
R6 and R8 are both listed as 100 ohm resistors (BRN-BLK-BRN), but
after installation, both show 61.6 ohms on three different
DMM's..while R7 which is a 68 ohm resistor is showing 50.1
I recognize all of them read slightly lower than their "listed"
values...but these seemed at such wide variance I didn't want to
continue until I knew whether I should be replacing them or not.
These three resistors all form a U around relay K12...so I didn't
know if the relay would be sucking down my readings...but I'm
placing the probe on the resistor wire on either side of the body
of the resistor...so I can't see how something else could be
causing that great of a difference....
the rest of the circuit that is in parallel with the resistor is
responsible for that variation.
Another identical 100 ohm resister still in the paper ladder to be
installed later in the sequence is giving me a 97 ohm reading...
And if you removed the ones you already soldered in, they would measure
close to the same 100 ohms (or 97 in your case.
Any advice would be appreciated.
David King
KE7EKA
K2 #6048
73 de Dave, W5SV
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