K2 problem, troubleshooting (alignment and signal tracing)

[Jason Marten]

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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[G3VVT]

 
In a message dated 12/03/05 22:33:23 GMT Standard Time,  [hidden email]
writes:

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?



--------------------------
 
The XG1 has not got sufficient output to carry out the test with the RF  
probe as it's maximum output is nominally 50uV PD (S9 cal test level). The 0.14V  
level given is 140mV (millivolt), or in the same designation as the XG1 in  uV
(microvolt) is 140,000uV. As you see the XG1 is quite a long way down on  
what is needed as it's purpose in life is rather different.
 
It has been suggested to build the crystal test oscillator shown in K2  
Appendix E, Troubleshooting page 9 figure 2. Not having gone down this  road have
not checked that even this test oscillator will make the  grade, but am pretty
sure that it should. None of my various signal  generators do the job either
as they do not have sufficient output  capability. Somewhere about 100mV PD
seems the maximum for most standard RF  generators. There are more specialised RF
generators available that can reach  the level required, though these are not
as widely available in most ham's test  equipment stock.
 
Bob, G3VVT
K2 #4168
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[Don Wilhelm-3]

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!
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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>
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> Elecraft web page: http://www.elecraft.com
>

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[David A. Belsley]

Jason:  You've already gotten some good comments.  Don is right to ask
if you're getting problems with the dummy load.  The fact that you are
bouncing your tv around sounds like you've got a somewhat makeshift,
and possibly unstable, antenna.  That could be causing the problem.  
One thing that I don't believe was mentioned has to do with the HI CUR
setting you've got.  If you have it at the setting given in the manual
(at least the earlier version of the manual I used with s/n 744), it is
likely to be very conservative.  You can raise it to 3.25 amps, and
that may help.  But don't do this until you get a decent antenna going.

best wishes,

dave belsley, w1euy



On Mar 12, 2005, at 5:32 PM, Jason Marten wrote:

> 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!
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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[Jason Marten]

Thanks for the info.

To clarify some things:

My indoor random wire antenna is _very_ makeshift.  My rigs hook up to an
LDG Z-11 tuner with coax, then on the tuner's output it goes to coax again,
which goes to a 4:1 balun.  One end of the balun goes to the antenna, the
other to some multiconductor rotator cable cut to different lengths for
different bands, thrown around the floor.  I think now the problem is not
with the TV, but with the speakers/DVD/receiver setup (made in China, I
presume) one of my roommates bought.  I used a very similar antenna before,
with a low pass filter, then took it down and used the wire for something
else.  The roommate bought the speakers, and then I later put up a very
similar antenna, lengthwise (both were from insulated speaker wire).  On SSB
on another commercial rig, the speakers were almost acting like a PA system.
  The end of the wire is on the other side of the wall opposite one of the
speakers and the receiver, maybe that's the problem.  I never noticed the
problems before the speakers arrived, when using 5W on another rig.

Connected to a dummy load, I do not get a HI CUR message at 5W.  When I
crank up the power to 15W, I get the HI CUR message at first, then it goes
away.  My K2 has the HI CUR setting at 2.5 amps (default).  Maybe I'll try
again with a higher value as suggested.  I was getting the HI CUR message
most of the time when hooked up to a yagi at my club's station.  I'm not
sure what the SWR of that antenna is, tho I wouldn't be surprised if it's
over 1.5:1.  I set the power there to 5W, and hit my CQ message and was
getting HI CUR a lot of the time.

In the receive pre-alignment, I'm pretty sure I found a peak on each of the
bands.  I'll try this again soon and record what happens.  In the
transmitter alignment part, however, I did notice the power output
increasing a lot with L9 on 30m and C23 on 20m, so much so that it went to a
HI CUR warning.  Most of the time for the other bands, output would increase
to maybe 2.3W on the peak.  I tried turning off TUNE when this happened, but
the problem repeated every time.

As for the voltage drop when tuning... when I set my K2 at 5W, here's the
receiving voltage and current:  13.4V, .24A.  When tuning, this changes to
12.8V, 1.66A.  The amps slowly start to rise, and after about 10 seconds or
so, it's reading 12.8V, 1.78A.  There's a really fat power cord (I think
it's 10 AWG) from the power supply to a RigRunner, but a 22 AWG cord from
that to the K2... I'll try that again with 16 AWG or bigger next time.

Thanks for all the help.


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[David A. Belsley]

> Connected to a dummy load, I do not get a HI CUR message at 5W.  When
> I crank up the power to 15W, I get the HI CUR message at first, then
> it goes away.

Jason:  It's probably not that the HI CUR situation "goes away."  The
power is likely responding to the HI CUR by resetting itself to a lower
level.  However, it is not uncommon for the HI CUR to occur at 15w with
the default limit setting of 2.5amps.  You can check the current draw
using DISPLAY to see if it exceeds the 2.5amp limit just before the HI
CUR state arises.  It is not likely to exceed 3.25, however.   So, once
you get a decent antenna going, raise the HI CUR limit to 3 or 3.25
amps and enjoy.


>  My K2 has the HI CUR setting at 2.5 amps (default).  Maybe I'll try
> again with a higher value as suggested.  I was getting the HI CUR
> message most of the time when hooked up to a yagi at my club's
> station.  I'm not sure what the SWR of that antenna is, tho I wouldn't
> be surprised if it's over 1.5:1.  I set the power there to 5W, and hit
> my CQ message and was getting HI CUR a lot of the time.

Well, that remains to be seen just what the swr of that yagi was. You
have a lot more faith than I have.  In any event, if you can drive your
dummy load to 15w with the HI CUR set to 3.25 amps, then you're most
likely just fine.  Give that a try.  You can monitor the situation
using the K2's current meter which shows when you hit DISPLAY.    If
the rig is drawing much more than 3.25 at 12-15w, you may have other
problems.  This is easy enough to check out.

best wishes,

dave belsley, w1euy
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[Jason Marten]

Ok, here's an update.

I raised the HI CUR limit to 3.0 Amps, and haven't seen a HI CUR warning
(except sometimes when power is set to 15 Watts).  I went through the Part
III Transmitter alignment, and was able to peak all of the L's and C's
without getting any HI CUR messages.

As a side note, I also measured my random wire antenna's length, and it was
pretty darn close to half a wavelength at 20 meters.  So, I cut a few feet
from it.  Haven't noticed any thumping on the TV anymore, tho I notice a
very slight amount of TVI on channels 3 and 4 (I have cable).  On other
channels, I can't see any effects.  This is with a low pass filter between
the K2 and my LDG Z-11 tuner.

I also tried using my MFJ-259B as a signal generator to continue on with the
BPF test with the RF probe.  I was able to get some values above 0 Vrms, but
the MFJ is so unstable I couldn't get any good readings.  But at least it
verified things were getting through.  Of course, I was able to listen to a
few QSO's on CW and PSK31 as well (like before) so I knew things were
working.

So, I think I was probably pretty good all along, I just needed to raise the
HI CUR limit a bit.  Thanks for all your time and help.


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