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K2/100 CAL acting up?

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TI2/NA7U

K2/100 CAL acting up?

My KAT2/100 seems to be acting up. Started noticing high SWR problems with a
tuned antenna, so ran further tests with a dummy load.

First thing is when I set Menu->AtU-CAL, I get high SWR readings. I thought
this was supposed to zero out/bypass the tuner. Clicking of relays is heard
but with a dummy load the SWR reading is 4:1 on the LED scale. It's also
pulling down the voltage as I clearly hear my outboard fan reduce RPM.

If I set it back to Auto, the high SWR remains until I hit TUNE, which
quickly takes it down to 1:1 (or something reasonable when using an antenna)
Sometimes, if the rig is in high power range I see a momentary HiCur flash
at first key down. My current level is set to 3.5A.

I have ample output power according to my wattmeter and have been making
QSOs, as I can tune out the phantom SWR, but probably I am making the
situation worse. Sometimes when I switch bands, the high SWR returns even
though the ATU memory should remember the band.

Can someone outline a diagnostic path to figure out where the problem may
lie? Fortunately, the KAT2/100 is outboard, which makes it easier to access
(K-Twins configuration).

TIA es 73,

Casey, TI2/NA7U

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Don Wilhelm

Re: K2/100 CAL acting up?

Casey,

It is a bit difficult to diagnose the KPA100 and the KAT100 when both
are in the EC2 enclosure.

Take the top off your K2 and connect the KPA100 directly to the base K2,
and do tests into a dummy load. Make certain that the Hi CUR messages
do not occur on any band with the power set to 100 watts.
You must do a TUNE/DISPLAY to obtain full power.
Put a wattmeter between the KPA100 and the dummy load and observe both
the K2 display and the external wattmeter. The power reading should be
within 20% of each other, and the SWR should be 1:1. If not, you should
null and then calibrate the KPA100 wattmeter first.

Next, put the QRP top cover on the K2 and test the KAT100 without the
KPA100 connected. Plug the control cable into the KIO2 and the KAT100
just as you would with the K2 'twins' - power the KAT100 from the 2.1mm
power jack.

Still working with the dummy load, balance the KAT100 wattmeter and
Balance (null) and calibrate it at 10 watts as indicated in the KAT100
manual. You will have to feed the base K2 into the KAT100 ANT1 and RF
IN jacks. Put the cable from the K2 back into the RF IN jack and the
dummy load to the ANT1 jack.
Then switch the ATU Menu to AUTO and tune all bands into the dummy load.

Put the KPA100 back in the EC2 enclosure and again test into a dummy
load on all bands.

hen go to your antenna and TUNE on all bands of interest. It should
tune to an SWR of less than 1.5.

Let us know where that testing goes awry.

If all goes successful up until you try to load the antenna, check your
antenna to see if it has any open connections, bad feedline, etc.

73,
Don W3FPR

On 11/5/2017 5:09 PM, TI2/NA7U wrote:

> My KAT2/100 seems to be acting up. Started noticing high SWR problems with a
> tuned antenna, so ran further tests with a dummy load.
>
> First thing is when I set Menu->AtU-CAL, I get high SWR readings. I thought
> this was supposed to zero out/bypass the tuner. Clicking of relays is heard
> but with a dummy load the SWR reading is 4:1 on the LED scale. It's also
> pulling down the voltage as I clearly hear my outboard fan reduce RPM.
>
> If I set it back to Auto, the high SWR remains until I hit TUNE, which
> quickly takes it down to 1:1 (or something reasonable when using an antenna)
> Sometimes, if the rig is in high power range I see a momentary HiCur flash
> at first key down. My current level is set to 3.5A.

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TI2/NA7U

Re: K2/100 CAL acting up?

Finally getting some time to work on this ...

In the first part when I connect the KPA100 directly to the base K2, where
does the AUX connector go? On the back of the AUX board (IOW, is it a
pass-thru) or should I remove the AUX board and connect to the control
board? Or, not connect it at all, just to P3 and P6?

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TI2/NA7U

Re: K2/100 CAL acting up?

In reply to this post by Don Wilhelm

I see that the small aux board must be removed as there is a "null" pin in
the plug and cable, so went ahead and did that and hooked up the KPA100 with
its RF out to the meter to the dummy load.

When I hold TUNE/DISPLAY, I get a display that looks like <x.y> <x.y - z>
with values when power is turned all the way down: 0.1 1.2-1 and all the way
up 4 2.1-1 Is that pwr and swr?

If I key down the display reverts to frequency immediately, so seems I can't
use TUNE/DISPLAY to monitor the power setting or key down output.

As I turn the power up or down I get HiCur almost constantly until I let go
of the power button. The behavior of the knob is not smooth, jumps a few to
several watts sometimes. Not sure if that's a dirty pot or a control board
problem.

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Don Wilhelm

Re: K2/100 CAL acting up?

In normal operation you cannot use TUNE/DISPLAY to monitor the power
output and SWR.

Yes, those values are the power and SWR as measured by the KPA100 wattmeter.

Given your readings along with the HI CUR messages, I believe there is a
problem with the KPA100 wattmeter.
To test that theory, connect an external wattmeter to the KPA100 and a
dummy load. Set the power to 50 watts (or 5 watts if powering only the
base K2).
Then do a TUNE. Do you have power control? Or does the power output go
to maximum (greater than 15 watts if only the base K2 is powered, or
greater than 120 watts if the KPA100 is powered.

If there is no proper power control, then the wattmeter in the KPA100 is
damaged. The most common cause is that KPA100 diodes D16 and D17 have
been damaged. If changing them does not cure the problem, then there
are other components that could be the problem.

Let us know what the results of your testing may be and we can help further.

73,
Don W3FPR

On 11/9/2017 6:08 PM, TI2/NA7U wrote:

> I see that the small aux board must be removed as there is a "null" pin in
> the plug and cable, so went ahead and did that and hooked up the KPA100 with
> its RF out to the meter to the dummy load.
>
> When I hold TUNE/DISPLAY, I get a display that looks like <x.y> <x.y - z>
> with values when power is turned all the way down: 0.1 1.2-1 and all the way
> up 4 2.1-1 Is that pwr and swr?
>
> If I key down the display reverts to frequency immediately, so seems I can't
> use TUNE/DISPLAY to monitor the power setting or key down output.
>
> As I turn the power up or down I get HiCur almost constantly until I let go
> of the power button. The behavior of the knob is not smooth, jumps a few to
> several watts sometimes. Not sure if that's a dirty pot or a control board
> problem.

TI2/NA7U

Re: K2/100 CAL acting up?

Do NOT have power control with KPA100, have power control with base K2

Diode voltage drop values using my DMM's diode test function (fwd/rev bias):
D16 .246/.278
D17 .151/.160

with diodes in place.

73,

Casey

On Thu, November 9, 2017 6:50 pm, Don Wilhelm wrote:

> In normal operation you cannot use TUNE/DISPLAY to monitor the power
> output and SWR.
>
> Yes, those values are the power and SWR as measured by the KPA100
> wattmeter.
>
> Given your readings along with the HI CUR messages, I believe there is a
> problem with the KPA100 wattmeter. To test that theory, connect an external
> wattmeter to the KPA100 and a dummy load. Set the power to 50 watts (or 5
> watts if powering only the base K2). Then do a TUNE. Do you have power
> control? Or does the power output go to maximum (greater than 15 watts if
> only the base K2 is powered, or greater than 120 watts if the KPA100 is
> powered.
>
> If there is no proper power control, then the wattmeter in the KPA100 is
> damaged. The most common cause is that KPA100 diodes D16 and D17 have been
> damaged. If changing them does not cure the problem, then there are other
> components that could be the problem.
>
> Let us know what the results of your testing may be and we can help
> further.
>
> 73,
> Don W3FPR
>
>
> On 11/9/2017 6:08 PM, TI2/NA7U wrote:
>
>> I see that the small aux board must be removed as there is a "null" pin
>> in the plug and cable, so went ahead and did that and hooked up the
>> KPA100 with
>> its RF out to the meter to the dummy load.
>>
>> When I hold TUNE/DISPLAY, I get a display that looks like <x.y> <x.y -
>> z> with values when power is turned all the way down: 0.1 1.2-1 and all
>> the way up 4 2.1-1 Is that pwr and swr?
>>
>> If I key down the display reverts to frequency immediately, so seems I
>> can't use TUNE/DISPLAY to monitor the power setting or key down output.
>>
>> As I turn the power up or down I get HiCur almost constantly until I
>> let go of the power button. The behavior of the knob is not smooth,
>> jumps a few to several watts sometimes. Not sure if that's a dirty pot
>> or a control board problem.
>

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