Bill,
All will be well as long as you give some liberty to the requested vs.
actual power output while you have the 1N4148 diodes in there - the
1N5711s are pretty flat with respect to voltage vs. frequency.
Glad to hear you now have a handle on things again.
73,
Don W3FPR
Bill Carpenter wrote:
I had some 1N4148 diodes in my junkbox so I installed them and all is
good again. The diodes in the KAT100 are fine so I'll order a few
1N5711s and replace the 1N4148s when they come in.
Thanks again!
----- Original Message ----- From: "Don Wilhelm" <[EMAIL PROTECTED]>
To: "Bill Carpenter" <[EMAIL PROTECTED]>
Cc: "elecraft list" <[email protected]>
Sent: Saturday, December 22, 2007 3:17 PM
Subject: Re: [Elecraft] Fw: Sudden erratic power/high current problems
with K2
Bill,
That is classic behavior when the KPA100 wattmeter diodes are zapped.
Since the most common failure cause is a static (lightning) surge
from the antenna, you may want to consider replacing the ones in the
KAT100 at the same time. The diodes are 1N5711s and in the KPA100
are D16 and D17 (near the SO239 jack), and the diodes in the KAT100
are D1 and D2.
As explanation for the behavior, the K2 power control loop senses
power at the output with the wattmeters - if there is zero power out
reported, the controls drive harder - so you have a base K2 trying to
drive as hard as possible and the resulting output power is the
maximum that can be produced on any given band. In other words, the
wattmeter must be working for the K2 to control the output power -
that is the sensing element.
73,
Don W3FPR
Bill Carpenter wrote:
After some investigation I found that the braid of the coax for the
Aux RF had frayed at the KPA100 board to just a couple of strands.
Hoping this was the problem I repaired it but no change. This all
seems to be caused by the K2 power control being all or none with no
intermediate settings. In low power as I turn the knob clockwise it
goes from minimal power to full QRP of about 12 watts suddenly and
when the high power comes on it jumps to full output. How do I
approach this problem? Is it ALC related?
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