[Elecraft] K3 Assembly Resistance Check is low

[Ron D'Eau Claire]

Brian, you are fine. The manual says "The following resistance checks
confirm that the main power busses in the K3 aren't shorted to ground."
Orienting your leads one way shows a very high value of resistance, so there
is definitely no short. 

You will encounter this situation a lot in building and troubleshooting.
Your DMM applies a small voltage to the circuit when measuring resistance.
Depending upon the circuit you are testing and your DMM, that voltage may
cause some junctions in various components to start to turn "on", causing
the measured resistance to drop. 

So, when checking for shorts, if you see a marginal reading, reverse the
leads and see what happens. If it meets specs that way, you are good to go. 

73 Ron AC7AC

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Brian F. Wruble
Sent: Saturday, May 18, 2013 10:26 AM
To: Elecraft Reflector
Subject: [Elecraft] K3 Assembly Resistance Check is low

My K3 fails the test on page 45 of the assembly manual.  The resistance from
a pin on U12 to ground is 447 ohms.  One of you asked a question ...
was the reading the same with the leads reversed?  The answer is no, that
reading is about 4.5 kohms, and it acts like the meter is charging a
capacitor in that direction.  It takes a long time for the meter reading to
settle down.

I put a fresh battery in the Fluke DMM, and I also tested a batch of 5%
tolerance 1/4 watt carbon resistors I had.  They all read a little low, none
read high, but none were low outside the 5% tolerance.

So, my reading of U12 to ground is 10% low.  The manual is pretty clear that
the resistance must be >500 ohms.

What is my next step?

Thanks.

Brian W3BW