[Elecraft] problem with K2, KAT100 and K2100PA combo

[Michael Carter]

Hi Brian,

Could you give a bit more detail?

You said the 'power went off on the K2' after
attempting to auto-tune the KAT100.  Do you
mean the DC power went dark on the K2 and
the screen display went blank, or something
else?

Have you tried to auto-tune the KAT100
at the low power level (set K2 Power control
less than 10 watts to yield 2 watt for
KAT100 tune)?

Have you tried connecting the KAT100  to
a good 50 ohm dummy load and doing
auto-tune at low and high power?

Does the K2 still 'talk' to the KPA100,
i.e. can you access the KPA100 menus?
If so, are there any Error/Status codes
displayed in the PA menu?  Can you
set the KAT100 to 'bypass' mode
and still get low power to a dummy load
on the KAT100?

The fact that the 12 VDC via the
PowerPoles doesn't reach the
base K2 suggests that diode D9
has opened.  It is also possible
that a collector-base short in
one of the PA transistors is
pulling down the 12V line.  This
begs the question: what are
you using for the DC power supply?

Although I have my KPA100 and KAT100
outboard of my K2, I have observed
situations where the KAT100 fails
to continue searching for a match
if the impedance seen at its output
is a very bad mismatch (high SWR).
In virtually all of those instances I can get the
KAT100 to properly auto-tune by
reducing the K2's Power control
to less than 10 watts (but more than
2 watts).

If you have an ohmmeter/multimeter,
you can check the resistance between
the PowerPoles with the 12 V power
supply disconnected at the PowerPoles
AND at the coaxial DC input.   That
resistance should be high - if not, one
of the PA transistors may have shorted
through.

Don't forget that the KPA100 manual
has troubleshooting procedures
and much more detail than I've
given here - see page 66 of the manual.

73,
Mike, K8CN