About 2 weeks ago a friend (Bill, W9LR) picked up K2 S#529 on Ebay for a
good price. I guess he fell in love with my K2, anyway being a good friend
I offered to update the radio and repair the problems with it. The 5dB pad
on the RF receive chain wasn't removed with the addition of the Noise
Blanker, so this had to be removed to improve the sensitivity. The mic jack
had to be rewired for the Heil Microphones. The display had to be
troubleshot to repair an intermittent digit. And a low signal problem was
traced to bad solder joints in the product detector circuit.
The radio came with Noise Blanker, Internal KAT, Internal Battery,
KSB2 and 160 meter modules. There were various build issues with the radio
to repair before I started on the upgrades.
The upgrades included: BFO Mod kit, VFO ALC 10M mods, Temp.
Compensated PLL Reference Upgrade, Matched Filter Crystals (both radio and
K2SSB), Keying Mod Kit, 2nd Filter upgrade, Firmware upgrade to 2.04, and
complete Rev A to Rev B mods. In addition Bill wanted to add the KIO2 kit,
so it was a chunk of work.
A number of things had to be dealt with before final alignment with
Spectrogram. There was a change in the windings of T7 from Rev A to Rev B
and although they shouldn't affect much, I rewound the torroid and noticed a
very quick 3dB improvement of signal. Of course the IF amp had to be
realigned after the SSB mods were also installed. After all of this was
done the sensitivity seemed fine but recovered audio levels were real low,
so this led me to work on the AGC circuit. Of course after shutting off the
AGC, the volume was booming, even louder than was possible before the Rev. B
mods. I modified the circuit to Rev B by adding a 50k pot in place of R1 on
the control board and set about setting the AGC level and S meter readings
to get good control and audio. At the same time I had to switch back and
forth from the S Hi and S Lo settings to get the meter to read properly at
S9 with 50 uV of signal from my service monitor.
After all this was dealt with, it was a piece of cake to hook up the
laptop and run spectrogram. I was astounded with the success, this radio
now hears and plays as an equal to my Rev B radio (#3075). I'm sure Bill is
going to have a blast with this. You'll probably hear him on the Fox Hunts
chasing down the Foxii with this rig now instead of his other rigs. (For
the last 4 weeks he'd been also using my KX1 to chase the Fox).
So Bill will probably pick the sucker up tomorrow afternoon so look
for him. And Bill welcome to the wonderful family of Elecraft.
Also a special thanks to Don Wilhelm, W3FPR, for his advice and help
via email while I was working out the bugs. Don is a veritable guru when it
comes to K2's and his knowledge is greatly appreciated. I learned a lot
from him and feel ever so more confident when I stick my fingers into
someone else's or my own K2.
73,
Gregg R. Lengling, W9DHI, Retired
Administrator http://www.milwaukeehdtv.org
K2/100 S#3075 KX1 S# 57
Member: ARRL, RSGB, RCA, WERA and ORC
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