KPA 500 runaway

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KPA 500 runaway

john@kk9a.com
I think I have the same issue with my K3S and KPA500. When changing bands the output is initially slightly higher during the first transmission and it then drops until the next band change. I do not use the KPA500 often and never looked into what the cause is.

John KK9A

From: cx7tt
Sat May 6 23:42:09 EDT 2017

I have almost same issue with K3S and KAT500/KPA500.

I only need about 22w max to get 500w on all bands except 40m where
drive must be 25/26w.
First couple of "dits" light up the 700w red LED but never trips the
amp. After that, it operates normally.
At first thought it was amp but discovered it was the K3S. It appears
after a band change but not all the time. First couple of dits show 40w
output, then normal after that.
Traveling now and when next home will see what happens when I use my
K2/100 with the amp.
Yes, have done the 5 and 50 w TX gain cal procedure, twice.

I also have low voltage of 56v and with tap at max for regular 110v
service. Ele support told me that below 60v should be ok, so I just live
with it. And with the occasional 700 LED lighting up. This has been
going on for over a year and with lot of operating, mostly cw, in
contests, running pile ups etc.
Yes, I do have several of CMC chokes by Balun  Design, My Antenna plus
extra two or three large chokes with 8 turns of RG8X passed thru. YC
would smile! 😎RF does not seem to be an issue here.
See QRZ.com HP1XT for description of antenna system.
Not wishing to hijack the thread; will be watching closely to see how
this is resolved.
73 y GL
Tom

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Re: KPA 500 runaway

Wes Stewart-2
Mine typically undershoots after a band change.

OTOH, if I set Config -> Tune Pwr to Nor, activate Tune and adjust the K3S to
drive the KPA500 to 500W for example, when I hit the key to transmit I get 600W.

Power control in the K3 is, shall we say, different from analog control and not
without its idiosyncrasies.

Wes  N7WS

On 5/7/2017 5:22 AM, [hidden email] wrote:
> I think I have the same issue with my K3S and KPA500. When changing bands the output is initially slightly higher during the first transmission and it then drops until the next band change. I do not use the KPA500 often and never looked into what the cause is.
>
> John KK9A
>

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