Posted by
Don Wilhelm-3 on
Mar 13, 2005; 12:06am
URL: http://elecraft.85.s1.nabble.com/K2-problem-troubleshooting-alignment-and-signal-tracing-tp375687p375692.html
First question - are you getting Hi Cur messages when the K2 is connected to
a dummy load? If not, all is well and the 'fault' is that the antenna
connected to the K2 must have an input impedance of close to 50 ohms. To
use the antennas you described, a tuner is a must. Do not try transmitting
into an antenna until you have properly aligned it using a good 50 ohm dummy
load.
The situation with the bandpass - did you find a peak when you did the
Receive Pre-alignment? If you found a peak on receive, all should be OK,
you just need to refine the peak on transmit - i.e. leave the inductor and
capacitor set where you peaked them during receive, you should find the
transmit peak very close to that setting. In other words, the peak for
receive and transmit are the same, but it is easier to find the peak on
transmit. The output will increase as you approach the peak - if it
increases a lot, drop out of "TUNE" and then press TUNE again - that will
re-level the power at 2 watts again.
If the reciever is behaving normally, and your problem is with the transmit
side of things, you should not have to do the receiver troubleshooting -
just move on to the transmitter part - and if I have described your problem
above, you may not have to do any troubleshooting at all - just finish the
alignment.
One thing to check when getting HI-CUR messages is the voltage of your power
source. With the K2, the current will INCREASE if the voltage decreases.
Be certain your power connections have very low resistance, and that you are
using 16 guage wire or larger. Check the voltage shown on the K2 display
during transmit conditions - it should read about 0.2 to 0.5 volts lower
than your power supply voltage because of the voltage drop across the
protection diode.
73,
Don W3FPR
> -----Original Message-----
>
> Ok, I've got a couple of problems here with my K2, I was
> wondering if anyone
> could help.
>
> I put together my K2, as best as I could. It receives fine (as
> far as I can
> tell) on a couple of bands that I've tried so far. I haven't
> really put it
> through the test of transmitting. However, it does heat up my
> dummy load,
> and causes the TV in the adjacent room to thump when hooked up to
> an indoor
> random wire (one reason why I haven't transmitted much!). I
> sometimes get
> HI CUR warnings, even when at 5 Watts.
>
> The only trouble I had with testing and alignment was under Part
> 3 of the RF
> board, under "Transmitter Alignment". My problem here, is that when I
> adjust L9 (30 meters) and C23 (20 meters) for maximum output, I
> don't really
> see a peak anywhere around 2 Watts, if I turn it just a little
> bit it goes
> way past 2 Watts until I get a HI CUR warning. I've tried this
> many times,
> and I always get the HI CUR warning. I decided to get L9 and C23
> close to 2
> Watts, and went on with aligning and testing.
>
> A little while ago, I brought my K2 into a club station, and even at 5
> Watts, I noticed I was getting HI CUR warnings a lot, so I
> stopped using it
> and I decided to go through troubleshooting (signal tracing and voltage
> checks) to try to see if I could find anything.
>
> I built the RF probe. "Preparation for Receiver Signal Tracing" (Pg 10)
> went fine. Same with "PLL Reference Oscillator and VCO" (Pg 10)
> and "BFO"
> (Pg 11).
>
> On "Low-Pass Filteass Filter, and T-R Switch", I have some questions and
> problems. It says to use a signal generator or test oscillator.
> Will the
> XG1 work here? This is what I was using, but it mentions setting
> the signal
> generator to 0.14 Vrms. Does this part not apply to the XG1, and which
> setting should I be using on the XG1?
>
> Then, when is says to hook up the probe to D6 and adjust the band pass
> filter for a peak reading (I was trying to adjust L1 and L2 for 40 meters
> using the XG1), I could not get any reading other than 0 volts. Also, on
> the following readings (W1, W6, both sides of D6, etc), I also
> kept getting
> 0 volts. I've been trying to look at the schematic to see where to look,
> but haven't been able to figure things out.
>
> Do I have some sort of problem with the Band Pass Filter? Where do you
> suggest I look for problems? Thanks!
>
>
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