Many moons ago when there was a K2 but no KPA100 I wanted to drive an
amp with my K2 and I needed a few more watts. I made some modification
(I don't remember the details) that allowed it to produce more than 20
watts, which made a big difference in output from my amp. I operated for
a while like that until the KPA100 came out, and it didn't seem to hurt
anything.
73,
Vic, 4X6GP
Rehovot, Israel
Formerly K2VCO
http://www.qsl.net/k2vco/
On 26 Feb 2017 01:02, Cameron Francey wrote:
Hi All,
I Just finished my Elecraft K2/10 build. I have lots of options to
add but the basic K2/10 is now working and I'll let it settle in for
a week or so to make sure its all ok before adding any options.
I started this build at the end of January, taking care to sort and
identify all the parts, especially the fixed value capacitors so it
made life much easier to select the correct values efficiently during
the build.
Everything went well, got the phase 1 and 2 tests done, added the
remainder of the components to finish phase 3 and then when I got to
the transmitter alignment step I noticed that rather than about 2
watts out as expected it was over 20 watts! Gee, what was wrong I
thought to myself? I had a quick look over everything, made 100%
sure all the components were installed correctly etc, but couldn't
find anything wrong. I even re-counted all the transformer winding's
and made sure they were all installed correctly. Nothing looked out
of place.
Having recently built two K1's and a K2/100 with KAT100 and nearly
every option available I knew it had to be something I had done
wrong. So I kept my logic head on and decided after my initial
disappointment and re-checking my work that a break away from the
bench was a good start.
Back to the bench this morning with a fresh mind I suspected that my
issue was somehow with the components that either set or control the
power level, and my reason for thinking that was because the issue
was present on every band and the power control pot made no
difference to the output power, and RX wise it was performing really
well so that eliminated a lot of the sections. Thinking about ALC or
the power control circuit on the control board I decided that was
where to start and work outwards from there. I knew the transmit
section of the main RF board was in good shape since it was capable
of producing more than 20 watts into a dummy load!
So, I read the circuit diagram, pulled out the control board and
started to trace the ALC circuit though the board.. That's when I
found my problem, I couldn't believe how stupid I had been and missed
soldering pin 2 of RP 3 on the Control Board, which is the ALC
feedback loop. After soldering that and re-testing all was well,
phew!!!
Where the lesson was learned was even though I'm close to obsessive
compulsive when identifying and selecting each component and double
checking twice before soldering anything, then checking with a
magnifying glass that the joints look good I still somehow managed to
let that un-soldered pin go unnoticed!
I don't think I have caused any adverse effects to the PA section
driving it so hard. The short periods of transmitting at about 23
watts never caused them to heat up. Its interesting that the PA
produced over 20 watts, so the 15 watts max output under normal
conditions seems quite a conservative level for those 2SC1969's.
Just thought I'd share my stupid mistake with the readers here and
that even being really careful things can still slip through the
net!
Best Regards,
Cameron, AF7DK/GM7LQR
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