K60XV

[John Wiener]

I continue to be baffled by my K60XV problem.  I have replaced R1 and  
C12.  I continue to get a short (zero ohms) between pins 13 and 14 on  
U1.  I thought I found a problem on the RF board: the coax shield may  
have shorted the lead from P1 lead 7 to ground...I insulated the coax  
shield exposed with tape.  My thought was to recommend that shrink  
tubing be used over the exposed shield on this side of the  
coax...similar to that used on the other side of the coax to the RF  
board.   However, I still get the short between pins 13 and 14 of U1  
on the K60XV without plugging it into the K2.

Can this be explained by a defective Z1?  Any other ideas?  Let's  
face it, there aren't too many components on this small board!  It's  
very frustrating.

John
AB8O
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[Don Wilhelm-3]

John,

Yes, a short between U1 pin 13 and pin 14 should be easy to find.  It will
most likely be either a solder bridge at those pins at the U1 socket or an
internal short in U1 itself, or a 'whisker' on the PC board.

The most efficient way to proceed is to remove U1 (use anti-static measures)
which will quickly tell you if the short is on the IC or on the board.

If the short stays with the board, you may want to try visually following
the PC board trace between U1 pin 13 and R1 first to see if it appears like
there might be a way that the trace can connect to anything else along its
path. The trace is on the top side of the board and runs partly under the
socket.  Look carefully with a strong light and magnifier and look at the
socket pins 13 and 14 on both sides of the board for any clue of a solder
bridge.

The PC trace between U1 pin 13 and R1 does not come near any other pin or
trace that carries the 6 volt rail, so I would judge the possibility of a
'whisker' from the trace to the 6V line is very low on the probability list
unless it occurs right between pins 13 and 14 of the U1 location.  You could
scrape the board between pins 13 and 14 a bit to be certain there is no
possibility of a connection - do that on boht sides of the board and if it
is an error in the board copper, you will have to scrape through the solder
mask coating and cut the connection between them.  Should that occur on the
top of the board, you would have to remove the socket to clear it.  Of
course, if you do find a copper 'whisker' between those points, that would
have been a board manufacturing error, and I am certain Elecraft would
correct it with replacements, but since the board is already built, I would
think it easier to just cut out the 'whisker' and be done with it.

73,
Don W3FPR

> -----Original Message-----
>
>
> I continue to be baffled by my K60XV problem.  I have replaced R1 and
> C12.  I continue to get a short (zero ohms) between pins 13 and 14 on
> U1.  I thought I found a problem on the RF board: the coax shield may
> have shorted the lead from P1 lead 7 to ground...I insulated the coax
> shield exposed with tape.  My thought was to recommend that shrink
> tubing be used over the exposed shield on this side of the
> coax...similar to that used on the other side of the coax to the RF
> board.   However, I still get the short between pins 13 and 14 of U1
> on the K60XV without plugging it into the K2.
>
> Can this be explained by a defective Z1?  Any other ideas?  Let's
> face it, there aren't too many components on this small board!  It's
> very frustrating.
>
> John
> AB8O
>

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