[Elecraft] K2 Build Question

Sat Jul 2 16:10:54 EDT 2005

Hi Tom,

There are some subtlties to making measurements of all sorts, but sometimes even simple one with a DMM!  I also thought I had a problem when measuring some resistances checks during the build of my K2 a few months back.  Turned out that I figured it would be more convenient to just move one probe around without having to hold the other on ground, so I let the ground lead sort of loosely sit in one of the 3D metal connectors while I proved with the other lead on the designated pins.  I too had some out of tolerance measurements, higher resistance than specified.  When I remeasured by clipping onto one of the "U" shaped ground leads directly on the board that I was doing measurements I found that everything was good.  

Another time I was getting very low resistance and intermittent measurements during another check.  That time I reallized that I had the board resting on some of the black conductive foam that IC's are mounted on during shipment.  The foam helped keep the board from moving around as much while I was probing, but the extra short circuits were not helpful in the measurements.  Note to self:  Don't power up any circuits while board is sitting on conductive foam!

73,

Mark, NK8Q
K2 4786 

>From: "tom.w3qs" <tom.w3qs at verizon.net>
>Date: Sat Jul 02 13:42:32 CDT 2005
>To: 'Margaret Leber' <maggie at voicenet.com>
>Cc: Elecraft at mailman.qth.net
>Subject: RE: [Elecraft] K2 Build Question

>Hi Maggie,
>
>Thank you so much for responding, I was afraid everyone was out fourthing.
>
>I seriously hoped you were wrong about checking the soldering on U1 as the
>pins are hidden by the glass-thing on the front side.
>
>But, I dutifully checked everything again and made an absolutely ghastly
>discovery!!!
>
>I can't operate a DMM!
>
>Seriously, I wouldn't have thought it would make a difference on resistance
>checking, but I guess that is not the case.
>
>I had done the checking by probing with the common lead while the other lead
>was grounded.   I reversed the connections, and now all checks are within
>normal range.  Many of the other checks are different, now, but they had
>been in-range before.
>
>Well, I guess you're never too old to learn something.  This is my first
>DMM, always done it with analog meters before.
>
>Thanks and have a great fourth!
>
>On to the rest of the adventure!
>
>Tom, W3QS
>
>-----Original Message-----
>From: Margaret Leber [mailto:maggie at voicenet.com] 
>Sent: Saturday, July 02, 2005 11:51 AM
>To: tom.w3qs
>Cc: Elecraft at mailman.qth.net
>Subject: Re: [Elecraft] K2 Build Question
>
>tom.w3qs wrote:
>
>> 1.  Resistance checks for U1 pins 1 & 2 are out of spec.  Chart says 
>> 25 - 35 K for both pins.  DMM reads 17 K for both.  Old analog meter 
>> reads 8 - 9 K for both.
>> 
>> 2.  Resistance checks for J1 pin 15 is out of spec.  Chart says 10 - 60 K.
>> Analog meter reads 80 K.
>> 
>> Perhaps the resistance chart does not take the added SSB stuff into
>account?
>> U1 pin 1 and J1 pin 15 are both associated with this added circuitry.
>
>I did the same build you did (well, on S/N 1641 anyway)...and noted the
>resistance check values after adding the KSB2 components using a Triplett
>2030A DMM.
>
>U1 pins 1 & 2 : 30Kohm
>J1 pin 15: 31Kohm
>
>So whatever the reason for what you're seeing, I don't think we can blame it
>on the KSB components being present. You might want to inspect things again.
>It's *very* easy to overlook soldering a pin or two on the LCD or one of the
>processor chips, and have things sorta almost work anyway because the pin's
>in a plated-through hole making intermittant contact. I did that more than
>once.
>
>  73 de Maggie K3XS
>
>-- 
>-----/___.   _)Margaret Stephanie Leber CCP, SCJP/"The art of progress /
>----/(, /|  /| http://voicenet.com/~maggie SCWCD/ is to preserve order/
>---/   / | / |  _   _   _    `  _  AOPA 925383/ amid change and to  /
>--/ ) /  |/  |_(_(_(_/_(_/__(__(/_      K3XS / preserve change amid/
>-/ (_/   '        .-/ .-/        ARRL 39280 /order."-A.N.Whitehead/
>/________________(_/_(_/_______AMSAT 32844_/<maggie at voicenet.com>/
>
>
>
>
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