Hi,
First, thanks for reading. Hopefully, it won't be boring for those
lucky K3 guys and gals...
CONFIGURATION
KX-1, 3080 upgrade. ATU currently removed and antenna jumper
installed for testing.Using XG-2 as a signal source. I have confirmed
the XG-2 seems to be working about as expected with another receiver
(about S-10 at 50uv and S-0 (but still in the speakers) at 1uv).
SYMPTOM
With normal operation, receive levels appear normal on 80 and 40 (I
can make contacts), but the XG2 is not peaking the KX-1's meter (I used
the XG-2 to calibrate the meter). 20 meters has always seemed deaf to
me. I don't remember how well the XG-2 was received on 20 when I
calibrated it. Here's the real "kicker": On 20 meters, with the XG-2
attached, I hear *no* volume difference between 50 and 1uv (which means
the KX-1's receiver is picking up the signal by proximity, not through
the antenna connection). If I touch the RX antenna connection almost
anywhere between the low-pass filter and the input of the Rx Mixer (U6,
pin 1), 20 meters comes way up (from nothing to receiving moderately
weak signals and noise). Touching the RX antenna line on 80 and 40
appears to have little or no affect. Output power on 20 meters does not
register full power, but I'm not sure if this is a calibration problem
as I don't have an accurate power meter. Also, when I couple a grid dip
meter into the RX, when tuned to 30 or 20 meters, I get a marked "dip"
just at about 17 MHz.
REASONING AND TROUBLESHOOTING
These are the things I've done and why...
1) Tested continuity between the antenna input and CA (measures
about 0.2 ohm). If I had messed up any of the connections on the 8030
coil board, I would have expected an open. 0.2 ohms *seems* consistent.
2) Disconnected leads A and B from the 3080 board (thought they
might have been interfering).
3) I inspected the 8030 coil board coil winding and installation.
They appear okay.
4) I checked that T2 is wound and installed correctly.
5) I have checked the values of capacitors in the low-pass filter
and mixer circuits (marked values only - not measured).
6) I've inspected the solder connections (connections seem to be
verified by continuity tests).
7) I've made sure the relays, K1 and K2, are in the proper state
("Normal" for 30 and 20 meters - Added capacitors are disconnected).
8) I've verified control voltages on the 8030 SMT board.
9) I've verified the 8030 SMT connections are to the proper places
(since I've disconnected the A and B wires and "injecting" a signal into
the Rx Antenna input seems to work well, I'm assuming that wire C is
not at fault).
10) I made sure D7 is properly installed. I expect if it was not,
I'd get no power out at all.
11) Scanned QTH's news group archive for KX-1 Rx problems, which had
some suggestions, but only one solution was listed. (I don't care for
their search facility)
OTHER
I'm sure I've missed something... probably obvious. I guess the next
step is to build an RF probe (though I expect the levels where the
problem is will be very difficult to measure) and drag down the boat
anchor Oscilloscope (which probably doesn't have the sensitivity to
trace the signal). Gives me an idea: I'll take my other radio and see if
I can trace the signal through the circuits. I expect I won't see it on
the RX ANT connection, which is telling me the same thing I think I'm
surmising above.
Okay. Well, that's all I can think of just now. If anyone has any
suggestions or comments, please feel free to contact me on and/or off list.
Thanks.
Regards,
kurtt
Kurt Pawlikowski, AKA WB9FMC
The Pinrod Corporation
[EMAIL PROTECTED]
(773) 284-9500
http://pinrod.com
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