Integrating my KXB3080

[Paul Neuman]

Rain was forecast for the entire Saturday before Labor Day and there
were no contests of interest so I decided to take the plunge and
integrate the KXB3080 module into my KX1.

To start off, it was a challenge to remove the KX1 board as I was afraid
of applying too much force.  I eventually popped it out, something I was
going to get quite good at.

I spent a good part of the afternoon slowly and carefully making the
required changes to the KX1 board and then installing the 3080 board.  I
had already built the two boards, using the main board as a warm up for
the KX1.

I powered up the KX1 after installing the module and enabled the two new
bands. Everything seemed ok but, when I went to perform the current and
voltage tests, found that my Radio Shack DMM had bit the dust.  I
probably inadvertently killed it.  I've since gotten a very nice
Meterman 37XR to replace it.

I took a leap of faith and decided everything was ok.  I did save the
LPF install for the next day when I would be fresh.  This was a bit
tricky but I soon had everything in place.

I used my XG2 to test and align 20M & 40M and peaked 30M using some
wire. The XG2 was a big help during the testing.    I had ordered it
after having  some trouble aligning the KX1 during the main build.  I
wish I had gotten it sooner but it definitely paid off here.

To my surprise, I was hearing signals on all bands.  Now to put the kx1
board back and try out the transmitter.

Once in the case, I noticed that there was something intermittent as
receive signal strength would suddenly drop out.  Transmit power output
was a fraction of a watt.  I noticed that pushing on the LPF caused the
drop in recieve signal so out came the board.  I figured a short was
causing both problems.

I carefully reviewed the LPF connections and found a couple of
questionable solder joints which I redid.  I also made sure the infamous
L2-1 wire was away from the nearby pad.  After these steps, the receiver
was now solid and I could wiggle the LPF around without any problem.

So I reinstalled it and tried the receiver before tightening the
standoffs.   All ok.  I tightened the standoffs and the signal strength
dropped as before.  I also found, when I put the bottom on, that
squeezing the case would cause the intermittent problem.

I spent quite a few hours trying to isolate the trouble.  I removed and
reinstalled the board a number of times.  There was no problem with the
board out of the case.    Only when I installed the board AND tightened
the standoffs would the problem occur.  I pretty much discounted the LPF
after awhile because I could manipulate it in all directions without
causing the problem.

I finally sent an email off to Garry at Elecraft asking for hints on
what to look at.  He suggested looking carefully at the LPF again and
perhaps using some tape to isolate any apparent short.

Even though I had carefully looked here many times with magnifier and
bright lights, I gave it another try.  I also looked for  possible
solder bridges or bad connections.  I reheated a couple of spots even
though they pretty much looked ok.

The L2-1 wire looked clear of the pad but I decided to put a piece of
tape between the wire and pad anyway.  It was a challenge to cut a small
enough piece to get down in there but I got it positioned and put
everything back together.

Problem solved! Evidently there was just enough pressure on the LPF when
the board was in the case to cause the short.  It is a mystery why I
couldn't make it happen out of the case. I guess it is possible that one
of my reheats solved the problem, but I really don't think that this was
the case.

Now I'm getting around 4 watts on all four bands.  20M output is
slightly lower, as is 80M, with 40M and 30M a bit higher. The SOC,
FISTS, and TN QP made a good testing ground this weekend and I made a
number of QSOs, some  on battery only.  I still need to make my first
30M qso.

Despite my rather frustrating problem, I did not find this was as
difficult as I had feared. The key was to go slow and be careful.  One
tip that Gary gave me was to tin the toroid wires in place.  I wish I
had had this advice sooner because I think it would've made for a
cleaner install, plus it would've averted my problem.

Don't let the 3080 scare you.  The KX1 was my first kit in many, many
years and it was a very rewarding yet doable challenge.  Now.. my
Rockmite just came in the mail today so on to the next project.

73...Paul, kd2mx


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