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" <[EMAIL PROTECTED]> >Date: Sat Jul 02 13:42:32 CDT 2005 >To: 'Margaret Leber' <[EMAIL PROTECTED]> >Cc: [email protected] >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:[EMAIL PROTECTED] >Sent: Saturday, July 02, 2005 11:51 AM >To: tom.w3qs >Cc: [email protected] >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_/<[EMAIL PROTECTED]>/ > > > > >_______________________________________________ >Elecraft mailing list >Post to: [email protected] >You must be a subscriber to post to the list. >Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > >Help: http://mailman.qth.net/subscribers.htm >Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
