Greetings
Since making my KPA100 some time ago I always had the odd
time when "HI CUR" would show, and I had tweaked the CAL CUR up to
3.74amps, but when I started getting the over current message again after
doing the latest PA mods and Firmware upgrade I decided it was time to find
out what was going on.
I thought the best option was to call in the "Heavies" straight away, so I
contacted Gary Surrency and received a prompt reply suggesting ( amongst
other things) that R26, the FWD cal pot in the KPA100 might be set too low.
Apparently if this is so, it allows more than 100 -110watts output from the
KPA100, which will demand more drive from the K2 and push the current
required up..
I am not exactly flush with good test gear now-days so I borrowed a watt
meter, and I was somewhat surprised to see I was delivering the best part
of 140w on 20m.
I tried the R26/R27 adjustment according to the manual, and it just didn't
seem to work out, so I contacted Gary again.
This time he suggested the R26 pot should show about 41 - 43k ohms to
ground, and the R27 pot should be set about 20% higher.
Mine was set to 36k, so I adjusted it to 42K (as a starting point) and
tried the output again. This time I was putting out around 110watts on 20m
and drawing only 3.2amps. Tests on all the other bands showed decent output
with reduced current readings, so I have left R26 where it is and put the
set back together.
Why I had the trouble setting R26 in the first place is a mystery. I have
made another K2/100 for a friend since I built my KPA100 and had no
problems with that alignment.
Anyway, I record this saga here in case someone else has been caught out
the same way? I imagine I made mine worse during the mods I did to the amp,
by most likely bumping R26 a tad lower.
I have Cal Cur set to 3.50amps now.......Where would we be without Gary?
Cheers.......Ron ZL1TW
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