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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