[Elecraft] KPA100 problem

[W3FPR - Don Wilhelm]

Steve,

First remove the regulator which you suspect anyway.  If that does not
remove the short, then start removing one component at a time until you find
it.  A good de-soldering tool makes the task a lot easier, and if the price
of the potential parts replacement is high, perhaps it is time to invest in
a de-soldering tool - you won't be sorry, and you can remove parts
non-destructively in most cases.

If you do not have a de-soldering tool, the easiest is to cut traces - start
by cutting a trace so it divides the suspect  components into 2 equal
groups, find out which half the short remains in and divide that section
into 2 groups again - you don't have to make as many cuts, and you will find
it more quickly.

I don't know of an easier method unless you happen to spot a solder bridge
along the way.

73,
Don W3FPR

> -----Original Message-----
.  When
> I remove U1 on the kpa100 board I get a dead short at pin 1 of U1.  This
> could mean that the 5 V regulator is bad but there are other components
> connected to this line and any one of these components could be defective
> (U3, U4, C23, C89, U6, etc).
>
> I am now faced with developing a procedure to isolate the bad
> part.  I have
> already inspected the board for shorts and do not see any.  The fact that
> the kpa100 worked before leads me to believe that a component may have
> shorted itself out.
>
> I could destructively remove each component until the short
> disappeared but
> then I would need to replace possibly a lot of parts.  The other option
> would be to isolate each part one at a time by cutting traces.  Once the
> part was deemed OK, I would have to patch the trace and go on to the next
> part.  I would end up with a lot of patched traces.
>
> Any suggestions?
>
> Thanks,
> Steve, W2MY
>
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