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KAT100 Tuning Failure

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KAT100 Tuning Failure

JeremyJones
After many months of flawless operation, my KAT100 is starting to have trouble tuning up, particularly on 40 and 80M.  It even has trouble tuning up a 50 ohm dummy load on these bands.

My normal setup is a 10W K2 with a KAT2, connected on the ANT 1 port to the AUX RF port of the KAT100 (mounted in an EC2 case with the KPA100).  This is internally connected to the KPA100.  The RF out from the KPA100 is then connected to the RF IN on the KAT100.  ANT 1 is connected to a DX-CC and ANT 2 is connected to an 80M Carolina Windom.

The first signs of trouble started when the SWR LEDs only lit intermittently.  The ANTENNA and PWR RANGE LEDs lit and operated correctly.  Gradually I stared seeing higher and higher SWR readings.

In order to narrow down the issue, I removed the KPA100 from the setup by connecting the KAT2 ANT 1 port directly to the KAT100 RF IN.  I disconnected the power from the KPA100 and independently powered the KAT100.  I removed the Windom from ANT 2 and connected a 50 ohm dummy load to see how the tuning compared with the antenna and the dummy load.  On 80M the dummy load gets 3:1 SWR with the DX-CC tuning up the same.  60M gets 2.3:1 for both.  40M gets 1.2 for the dummy load and 3:1 for the DX-CC.  30M and up seem to tune ok.

I tried doing the troubleshooting steps in the manual, starting with ATU INIT.  I scrolled through L0-L8 and C0-C8 and N1-N2 and the relays functioned for each.  I tried doing the individual test for the inductors and relays, but there was no change in SWR with multiple components, so either I was doing it wrong, or the fault is bigger than a single component.

I've tried to be as detailed as possible here, so any help is appreciated, and if there are any suggestions or any other info required please let me know.  I'd like to get this back on the air as its my only radio!
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Re: KAT100 Tuning Failure

Phil Wheeler-2
Be sure to check all the cables or try changing
them out one by one, Jeremy.

Phil W7OX

On 7/17/15 10:05 AM, JeremyJones wrote:

> After many months of flawless operation, my KAT100 is starting to have
> trouble tuning up, particularly on 40 and 80M.  It even has trouble tuning
> up a 50 ohm dummy load on these bands.
>
> My normal setup is a 10W K2 with a KAT2, connected on the ANT 1 port to the
> AUX RF port of the KAT100 (mounted in an EC2 case with the KPA100).  This is
> internally connected to the KPA100.  The RF out from the KPA100 is then
> connected to the RF IN on the KAT100.  ANT 1 is connected to a DX-CC and ANT
> 2 is connected to an 80M Carolina Windom.
>
> The first signs of trouble started when the SWR LEDs only lit
> intermittently.  The ANTENNA and PWR RANGE LEDs lit and operated correctly.
> Gradually I stared seeing higher and higher SWR readings.
>
> In order to narrow down the issue, I removed the KPA100 from the setup by
> connecting the KAT2 ANT 1 port directly to the KAT100 RF IN.  I disconnected
> the power from the KPA100 and independently powered the KAT100.  I removed
> the Windom from ANT 2 and connected a 50 ohm dummy load to see how the
> tuning compared with the antenna and the dummy load.  On 80M the dummy load
> gets 3:1 SWR with the DX-CC tuning up the same.  60M gets 2.3:1 for both.
> 40M gets 1.2 for the dummy load and 3:1 for the DX-CC.  30M and up seem to
> tune ok.
>
> I tried doing the troubleshooting steps in the manual, starting with ATU
> INIT.  I scrolled through L0-L8 and C0-C8 and N1-N2 and the relays
> functioned for each.  I tried doing the individual test for the inductors
> and relays, but there was no change in SWR with multiple components, so
> either I was doing it wrong, or the fault is bigger than a single component.
>
> I've tried to be as detailed as possible here, so any help is appreciated,
> and if there are any suggestions or any other info required please let me
> know.  I'd like to get this back on the air as its my only radio!

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Re: KAT100 Tuning Failure

Don Wilhelm-4
In reply to this post by JeremyJones
Jeremy,

You must remove the ribbon cable to the KPA100 to remove it from the
path - I suggest physically removing it from the EC2 enclosure just to
be safe.  The fact that you had the KPA100 partly in the path during
your tests could create invalid observations.
Use a dummy load for testing rather than an antenna.

If you are getting funny SWR LED indications, the first suspect is D1
and D2 in the KAT100.  Those are 1N5711 diodes, and if you have some in
your parts supply, I would just replace them.  I know it is a 'bear' to
get to the solder side of the board when mounted in the EC2 enclosure,
so see if there is enough lead length above the board to break the
diodes and solder new ones in their place.

You would get a better picture of the operation of the KAT100 wattmeter
if you remove the KAT2 (just unplug it from the KIO2 AUX board).  Then
connect the KAT100 control cable and connect the K2 lower panel BNC to
the KAT100 RF in.
The KAT100 will then respond like the KAT2 normally does and in ATU CALP
or CALS will show you the wattmeter readings - connect ANT1 to a dummy
load for that test.  It is advisable to connect an inline wattmeter
between the KAT100 and the dummy load.  If the internal wattmeter in the
KAT100 is not functioning properly you will be able to calibrate it.

73,
Don W3FPR

On 7/17/2015 1:05 PM, JeremyJones wrote:

> After many months of flawless operation, my KAT100 is starting to have
> trouble tuning up, particularly on 40 and 80M.  It even has trouble tuning
> up a 50 ohm dummy load on these bands.
>
> My normal setup is a 10W K2 with a KAT2, connected on the ANT 1 port to the
> AUX RF port of the KAT100 (mounted in an EC2 case with the KPA100).  This is
> internally connected to the KPA100.  The RF out from the KPA100 is then
> connected to the RF IN on the KAT100.  ANT 1 is connected to a DX-CC and ANT
> 2 is connected to an 80M Carolina Windom.
>
> The first signs of trouble started when the SWR LEDs only lit
> intermittently.  The ANTENNA and PWR RANGE LEDs lit and operated correctly.
> Gradually I stared seeing higher and higher SWR readings.
>
>

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Re: KAT100 Tuning Failure

JeremyJones
In reply to this post by JeremyJones
Ok, so I've removed the KPA100 completely, and disconnected the KAT2 serial and RF connections.  I connected my W2 watt meter on the output of ANT2 of the KAT100, and the LOAD side of the sensor to a 50 ohm dummy load.  The readings and indications I got are as follows:

160M 1.00:1 No LED indication on KAT100.  K2 showed 1.0:1
80M 1.00:1 No LED indication on KAT100.  K2 showed 1.0:1
60M 1.00:1 LEDs on KAT100 flickered a bit and remained off once tuning was finished.  K2 showed 5.6:1
40M 1.00:1 LEDs on KAT100 flickered a bit and remained off once tuning was finished.  K2 showed 5.6:1
30M 1.00:1 LEDs on KAT100 flickered a bit and finally lit 2.  K2 showed 2.3:1
20M 1.00:1 LEDs on KAT100 lit as expected and finally lit 1.  K2 showed 1.2:1
17M 1.00:1 LEDs on KAT100 lit as expected and finished at 1.  K2 showed 1.0:1
15M 1.00:1 LEDs on KAT100 lit as expected and finished at 1.  K2 showed 1.0:1
12M 1.05:1 LEDs on KAT100 lit as expected and finished at 1.  K2 showed 1.0:1
10M 1.00:1 LEDs on KAT100 lit as expected and finished at 1.  K2 showed 1.0:1

I'm still digging around for the diodes, but if I haven't found any by tomorrow I'll be putting in an order to digikey.
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Re: KAT100 Tuning Failure

JeremyJones
In reply to this post by JeremyJones
What are the specs for the diodes?  I'm seeing 70V 15mA as the common size.
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Re: KAT100 Tuning Failure

Don Wilhelm-4
Jeremy,

Do not order alternatives for use in the wattmeters.  Use only 1N5711s
if you want the best voltage response vs. frequency.
Those parameters are not specified.  Elecraft chose those diodes long
ago based on testing for that frequency response.
If you are looking for alternatives, and do not care about the readings
obtained at lower power levels (QRP), then you could use 1N4148 diodes
which are plentiful.

73,
Don W3FPR

On 7/20/2015 7:31 PM, JeremyJones wrote:
> What are the specs for the diodes?  I'm seeing 70V 15mA as the common size.
>
>

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Re: KAT100 Tuning Failure

Don Wilhelm-4
In reply to this post by JeremyJones
Jeremy,

Hopefully you had the ATU menu set to CAL for those tests.  If not,
please re-do the measurements.
Assuming that you were set for ATU CAL, I can offer these comments:
With the configuration you have now - KAT2 and KPA100 out of the
picture, those results indicate that 1) the KAT100 wattmeter is not
properly balanced and calibrated, or 2) something in the KAT100
wattmeter has been damaged - most likely diodes D1 and D2.
It is possible that the diodes have been 'partially damaged' and have
become frequency sensitive.
With a dummy load connected and the ATU menu set to CAL, you should have
a 1.0 SWR on all bands.
The fact that you do not says that either the wattmeter is not properly
balanced, or one or both diodes are bad, or that there is some random
L/C element stuck in the path to he dummy load (that would be a relay
problem).

I would arbitrarily replace D1 and D2, and then attempt to balance and
calibrate the KAT100 wattmeter as indicated in the KAT100 manual.
If you cannot achieve a good null when balancing, just stop - attempting
further steps is futile until you can obtain a good null.

73,
Don W3FPR

On 7/20/2015 7:15 PM, JeremyJones wrote:
> Ok, so I've removed the KPA100 completely, and disconnected the KAT2 serial
> and RF connections.  I connected my W2 watt meter on the output of ANT2 of
> the KAT100, and the LOAD side of the sensor to a 50 ohm dummy load.  The
> readings and indications I got are as follows:
>
>

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Re: KAT100 Tuning Failure

JeremyJones
In reply to this post by Don Wilhelm-4
The diodes I was looking at were 1N5711, but they were either 70V 15mA (http://www.digikey.ca/scripts/DkSearch/dksus.dll?Detail&itemSeq=176360177&uq=635730153536694158) or 70V 33mA (http://www.digikey.ca/product-search/en/discrete-semiconductor-products/diodes-rectifiers-single/1376383?k=1n5711).

I just want to make sure I get one with the proper rating.

I did not have the KAT100 in CAL mode.  Guess I'll be redoing the tests and posting the results shortly.
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Re: KAT100 Tuning Failure

Ken G Kopp
Jeremy, why not order the diodes from Elecraft and be sure you get the
correct ones?

73!

Ken - K0PP
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Re: KAT100 Tuning Failure

Don Wilhelm-4
In reply to this post by JeremyJones
Jeremy,

Your first link resulted in an error 404, but the 2nd showed a diode
that I believe may be a specialty version. It was highly overpriced at
over $11 each.  The Aligent data sheet for the 1N5711 shows it to be a
15 ma device.
You would do better to order from Elecraft.  Order E560004 - Diode,
1N5711, small glass body from [hidden email].  Order 2 of them (or
possibly 4 since you do not yet know the status of those in the KPA100).

An alternate source is "The Toroid King" http://www.partsandkits.com.  
Diz prices his 1N5711 diodes at 10 for $2 (plus shipping).
I have purchased those diodes from Diz for a long time - never a problem.

Yes, those test results are not valid unless the KAT100 was in CAL - in
any other setting there would have been L and C elements active, and the
goal is to test the wattmeter as the first step.

73,
Don W3FPR


On 7/20/2015 7:59 PM, JeremyJones wrote:

> The diodes I was looking at were 1N5711, but they were either 70V 15mA
> (http://www.digikey.ca/scripts/DkSearch/dksus.dll?Detail&itemSeq=176360177&uq=635730153536694158)
> or 70V 33mA
> (http://www.digikey.ca/product-search/en/discrete-semiconductor-products/diodes-rectifiers-single/1376383?k=1n5711).
>
> I just want to make sure I get one with the proper rating.
>
> I did not have the KAT100 in CAL mode.  Guess I'll be redoing the tests and
> posting the results shortly.
>
>

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Re: KAT100 Tuning Failure

JeremyJones
Ok, redid the tests in CAL mode with the following results:
160M 1.03:1 No LED indication on KAT100.  K2 showed 1.0:1  Hi Current warning
80M 1.03:1 No LED indication on KAT100.  K2 showed 1.0:1  Hi Current warning
60M 1.02:1 No LED indication on KAT100.  K2 showed 1.0:1  Hi Current warning
40M 1.03:1 LEDs on KAT100 lit up to 3.   K2 showed 3.0:1  Hi Current warning
30M 1.03:1 LEDs on KAT100 lit up to 3.   K2 showed 3.0:1  Hi Current warning
20M 1.00:1 LEDs on KAT100 lit up to 2.5. K2 showed 2.6:1  Hi Current warning
17M 1.04:1 LEDs on KAT100 lit up to 1.7. K2 showed 1.8:1  Hi Current warning
15M 1.04:1 LEDs on KAT100 lit up to 2.   K2 showed 2.0:1  
12M 1.05:1 LEDs on KAT100 lit up to 1.7. K2 showed 1.8:1  
10M 1.06:1 LEDs on KAT100 lit up to 2.   K2 showed 2.0:1

I guess ordering from Elecraft is the safest bet.  It will take a bit longer, but so be it.
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Re: KAT100 Tuning Failure

Don Wilhelm-4
Jeremy,

The wattmeter in the KAT100 has been damaged - diodes D1 and D2.
You also have the KPA100, and it has a wattmeter with those diodes - so
order 4 just in case those need to be replaced too.
We can get to the KPA100 after the KAT100 has been taken care of.

Failure to disconnect the antenna from the K2 when not in use will
damage those diodes from static coning in from the feedline(s).

73,
Don W3FPR

On 7/20/2015 8:36 PM, JeremyJones wrote:

> Ok, redid the tests in CAL mode with the following results:
> 160M 1.03:1 No LED indication on KAT100.  K2 showed 1.0:1  Hi Current
> warning
> 80M 1.03:1 No LED indication on KAT100.  K2 showed 1.0:1  Hi Current warning
> 60M 1.02:1 No LED indication on KAT100.  K2 showed 1.0:1  Hi Current warning
> 40M 1.03:1 LEDs on KAT100 lit up to 3.   K2 showed 3.0:1  Hi Current warning
> 30M 1.03:1 LEDs on KAT100 lit up to 3.   K2 showed 3.0:1  Hi Current warning
> 20M 1.00:1 LEDs on KAT100 lit up to 2.5. K2 showed 2.6:1  Hi Current warning
> 17M 1.04:1 LEDs on KAT100 lit up to 1.7. K2 showed 1.8:1  Hi Current warning
> 15M 1.04:1 LEDs on KAT100 lit up to 2.   K2 showed 2.0:1
> 12M 1.05:1 LEDs on KAT100 lit up to 1.7. K2 showed 1.8:1
> 10M 1.06:1 LEDs on KAT100 lit up to 2.   K2 showed 2.0:1
>
> I guess ordering from Elecraft is the safest bet.  It will take a bit
> longer, but so be it.
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KAT100-Tuning-Failure-tp7605018p7605174.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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Re: KAT100 Tuning Failure

JeremyJones
Parts are on order.  I'll update once I have the diodes swapped.  Thanks for the help thus far.
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Re: KAT100 Tuning Failure

JeremyJones
Ok,  I received the new diodes today and have installed them into the KAT100.  Running the tests in CAL mode has the LED indicators on the KAT100 matching what the display on the K2 reads, as well as matching the W2 watt meter.  Is there anything else I should be looking at before starting to put things back together?
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Re: KAT100 Tuning Failure

Don Wilhelm-4
It sounds to me like all should be well.

As a refinement ---
If you have 2 50 ohm dummy loads and a coax TEE adapter, you could put
the dummy loads in parallel to produce a 25 ohm dummy load. That will
give you a sanity check on the Reflected trimmer pot calibration -
adjust it to light the SWR=2 LED.

Note that the power and SWR displayed on the K2 come from the KPA100 and
not the KAT100.

73,
Don W3FPR

On 8/10/2015 6:14 PM, JeremyJones wrote:
> Ok,  I received the new diodes today and have installed them into the KAT100.
> Running the tests in CAL mode has the LED indicators on the KAT100 matching
> what the display on the K2 reads, as well as matching the W2 watt meter.  Is
> there anything else I should be looking at before starting to put things
> back together?
>

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Re: KAT100 Tuning Failure

JeremyJones
Thanks Don.  The KPA 100 is still disconnected.  I have the base K2 with KAT2 connected to the KAT100 in the EC2 chassis.  This normally has the KPA100 on top, but was removed as suggested to perform the troubleshooting.

I don't have an extra dummy load at this time, but I am going to see if I can borrow one and test as you suggested.
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Re: KAT100 Tuning Failure

Don Wilhelm-4
Since you have the KPA100 disconnected and the KAT100 connected to the
KIO2 for control, the KAT100 with the K2 ATA menu in CAL, you can
calibrate the KAT100 much like the KAT2 for wattmeter balance and
forward power.

Connect the K2 to the RF IN and a dummy load and inline wattmeter to ANT1.
Set the power to 8 or 10 watts, and do a TUNE.
Measure the voltage at U5 pin 5 and adjust C1 to achieve a minimum
voltage - it should be close to zero volts.
Then set R3 (forward trimmer pot) so the K2 display agrees with the
power indicated on the external wattmeter.

Since you do not have 25 ohm or 100 ohm dummy loads, power off the K2
and measure the resistance from U5 pin 3 to ground.  Then multiply that
resistance by 1.2 (remember that value).
Then measure the resistance between U5 pin 3 to ground and adjust R4 to
produce the resistance value you calculated.

It does sound like you have things adjusted close to optimum, but a
double check will do no harm.

If you do find another dummy load to create a 25 ohm dully load, you can
touch up the R4 (REFL) trimmer pot to properly indicate an SWR of 2.0.
If by that time you have the KPA100 inline, you still can do it with the
KPA100 "on it's back" to the right of the EC2 enclosure (supported on a
boox or box about half the height of the enclosure).  If you do it with
the KPA100 inline, adjust R4 so the KAT100 LEDs indicate an SWR of 2.0
and ignore the K2 display.  With the KPA100 inline, the K2 display will
show the power and SWR seen by the KPA100 wattmeter, not the KAT100.

73,
Don W3FPR

On 8/10/2015 8:25 PM, JeremyJones wrote:
> Thanks Don.  The KPA 100 is still disconnected.  I have the base K2 with KAT2
> connected to the KAT100 in the EC2 chassis.  This normally has the KPA100 on
> top, but was removed as suggested to perform the troubleshooting.
>
> I don't have an extra dummy load at this time, but I am going to see if I
> can borrow one and test as you suggested.
>
>

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