[Elecraft] K2 troubleshooting

[Tom Hammond]

Hi John:

>Now, as I was reviewing solder joints, etc., I noted that one of the
>solder pads for C4 was touching the outer can tab of L1.
>My question:
>
>Is this a solder bridge, or is there supposed to be a connection
>between C4 pad and outer (ground) tab of L1?
>I looked on N0SS's PCB pix and I cannot tell if a connection exists
>there or not.  (thanks, by the way, to Tom for the pix).

Fast answer... YES! They're supposed to be touching.

Here's how to use the pic to help... that is, IF you have a suitable 
graphics program (or viewer):

  1) Load both the TOP and BOTTOM views of the PC board in question.

  2) LOCATE the component(s) in question of the side of the PC board
     which includes the silkscreened nomenclatures.

  3) ENLARGE the (TOP SIDE) image so that most of your screen is occupied
     by the component pads in question.

  4) ENLARGE the BOTTOM SIDE image to the same size.

  5) FLIP the TOP SIDE image HORIZONTALLY. Of course, now all the print
     is reversed, but you should be able to re-locate the components in
     question by merely SLIDING the image right or left (flipping side
     to side usually won't cause the image to move up/down).

  6) Make the image FULL SCREEN.

  7) Switch to the BOTTOM SIDE image and (using the relative scroll bar
     positions of the drag bars from the TOP SIDE image) position the
     bottom side image so you can place the pads for the component in
     question immediately beneath those of the TOP SIDE image. You can
     usually use CTRL-TAB to toggle between the two images, so you can
     easily tell if the two sets of pads are aligned, one above the other.

  8) With the two images properly aligned, you can now quickly switch
     between top/bottom views in order to get a really CLOSE look at the
     pads and land connections between them.

I use this method all the time when doing signal path tracing on the 
PC board itself.

In regard to your particular question, if you find a case where it 
appears that two pads are touching, check both top and bottom. If the 
pads appear to be so close together that they'd almost have to be 
touching, it's a pretty guess that they're supposed to be that way... 
especially given that NO OTHER UN-CONNECTED pads are anywhere nearly 
as closely spaced.

Finally, check out the schematic!!!  If (as it does in this case) the 
schematic indicates that one end of C4 connects to L1 AND to ground, 
then you've just answered your question WITHOUT having to resort to 
the images. All the images do then is to confirm that one end of C4 
is attached to the (grounded) metal cover lug of L1, and that one end 
of L1 is also connected at the same point.

Since the reflector doesn't support file attachments, I'm sending you 
some blown-up images of the parts of the PC board in question.

73,

Tom Hammond    N0SS