Andrew,
One way to check check for continuity between the KPA100 VRFDET signal
and the base K2 is to check the voltage at KPA100 U6 pin 6 and The base
K2 Control board U6 pin 2 - they should be the same.
If not there is a broken wire connection or U6 (MCU) has a problem
(failure).
If U6 has a failure at pin 2, you will have power problems with the base
K2 (no KPA100 installed) as well - no proper power control.
73,
Don W3FPR
On 7/27/2026 5:38 PM, Andrew Lenton wrote:
See comments on brackets
KR
Andrew
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On July 27, 2026, at 20:11, W3FPR <[email protected]> wrote:
Andrew,
With the KPA100 installed, and the power set to 10 or 11 watts, what is
the actual power output in TUNE?
It should be near 2 watts. (True this is fine.)
If not, there is a problem in the VRFDET section of the KPA100 or in the
base K2.
First, remove the KPA100 (physically) and try it with just the base
K2. (Works fine)
If the base K2 is OK, then yoou have some KPA100 problem to solve. Put
the KPA100 upside down on a box or book about 1/2 the height of the K2
and remove the shield. ( All done works fine)
set the power to about 50 watts and prepare to do some voltage
measurements. ( 50 Watts set up)
(I will do this)
Measure the voltage at U5 pin 5 - then at 5 pin 7, they should be close
to the same voltage.
U6 pin 3 should be about 1/2 that voltage. If not, the problem is Q10
( Only see the problem after I put the PA back on the K2)
and possibly Q11.
If all OK this far, then make certain U6 pin 8 is near 5 volts.
If so, then check U6 pin 6 and tell me what the voltage there actually
is. U6 is a common failure.
73,
Don W3FPR
On 7/26/2026 1:16 PM, Andrew Lenton via Elecraft wrote:
Hi I have just performed all the mods on the KPA100 and reset the FWD
and REF and set the bias at 400mA, my bird watt meter tracks the
indicated power on the K2
After fitting the screen and putting it all back together it works
fine on SSB.
On low power tune is fine, however on more than 11 Watts pressing
tune causes the power to jump to 140 and the SWR 2.2:1, so suspecting
it is "hooting" when all back together.
Before I dive in an suggestions?
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