Damaged KPA-100

[Daniel Solano Gómez]

Hello, all,

I recently acquired an external KPA-100/KAT-100 for my K2.  It was working perfectly at the time of purchase, but I must have done something really wrong when I was getting it set up at home.  I am running into the following two errors:


KPA-100 T-R switch problem
==========================

The symptom that I am seeing is that in high power mode there is no output and, if the power is much above 11W, the K2 will present “HI CURR”.  Low power transmit seems fine, and receive seems fine in both high and low power.  The KPA-100 is has not been upgraded to revision B, and is running firmware version 1.06.

I did find and repair a couple of issues:

1. I replaced D-12, as it was broken in two.
2. One end of R19 had come loose, and it has been resoldered.

I moved the KPA-100 into the K2 to eliminate the KAT-100 from the mix.

The voltages on D11-D14 are off as follows (tuned to 40m, 14.1V power supply, low power TX is 0.1W, high power TX is 11W):

D11:
  * Anode:
    * At low power, the anode seems fine in RX/TX.
    * In high power, the RX voltage seems fine at about 1.7V, but in TX it is going up to 13.9V instead of of being around 1.6V.
  * Cathode:
    * In low power RX, it is 149V instead of 14.0V.  It dips slightly in TX.
    * At high power RX, it is high at 136V instead of 14.0V.  TX voltage is also high at about 81V instead of 0.8V.

D12:
  * Anode:
    * At low power, the anode seems fine in RX.  I am not seeing the dip in low power TX from 14.1V to 13.9V.
    * In high power, the RX voltage seems fine at about 1.7V, but in TX it is going up to 13.9V instead of of being around 1.6V.
  * Cathode:
    * At low power, the RX voltae is a bit high, about 144V instead of 119V.  The voltage does dip slighltly in TX.
    * In high power, the voltages seem roughly correct (0.9V RX/121V TX)

D13:
  * Anode:
    * It seems fine at low power, staying at about 14.1V.
    * At high power, it also seems fine, going up from about 1.7V RX to 14V TX.
  * Cathode:
    * At low power, the RX voltage is high at about 148V instead of 14.1V and dips slightly on TX.
    * At high power, the RX voltage is high at about 136V instead of 14V.  At TX it drops to about 60V.

D14:
  * Anode:
    * At low power, it seems fine at RX, 14.1V.  I am not seeing the TX dip.
    * At high power, it also seems fine, going up from about 1.7V RX to 14V TX.
  * Cathode:
    * At low power, the voltages seem a touch high at 144V TX/143V RX instead of 117V/116V.
    * At high power, the RX/TX voltages seem about right at 0.9V/120V.

So, it seems to me there is an issue with biases on the T-R switch diodes.  I definitely hear a click when moving between high and low power modes, but I am not hearing anything on transmit.  I don’t know if I should.


KAT-100 startup issue
=====================

This one isn’t as big of an issue, as I have a workaround.  When the KPA-100 was installed with the KAT-100 in the EC-2 enclosure, the KAt-100 never seemed to fully “boot” if the K2 was powered on with the power knob in the 0.1-10W range.  It would be stuck in a transmit-like state with the the antenna 1, SWR 1, and power range low LEDs lit.  Transmit wouldn’t work, and all of the LEDs on the K2’s power meter would also remain lit.  If the K2 is powered on with the power level set higher than 10W, then it seems to move past that point and enter normal operation.


Thank you for taking the time to read through this.  I am a bit of a beginner, so it’s a bit of a challenge for me to diagnose and resolve these issues.

73,

Daniel, AG5UT
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[David Gilbert]

I don't have a K2 and know nothing about them, but if R19 got hot enough
to come unsoldered I'd be surprised if it was still any good.

And if D12 broke, it probably got really hot due to over current as
well, so anything in either of those paths is suspect.

73
Dave   AB7E


On 10/2/2019 8:07 PM, Daniel Solano Gómez wrote:

> Hello, all,
>
> I recently acquired an external KPA-100/KAT-100 for my K2.  It was working perfectly at the time of purchase, but I must have done something really wrong when I was getting it set up at home.  I am running into the following two errors:
>
>
> KPA-100 T-R switch problem
> ==========================
>
> The symptom that I am seeing is that in high power mode there is no output and, if the power is much above 11W, the K2 will present “HI CURR”.  Low power transmit seems fine, and receive seems fine in both high and low power.  The KPA-100 is has not been upgraded to revision B, and is running firmware version 1.06.
>
> I did find and repair a couple of issues:
>
> 1. I replaced D-12, as it was broken in two.
> 2. One end of R19 had come loose, and it has been resoldered.
>
> I moved the KPA-100 into the K2 to eliminate the KAT-100 from the mix.
>
> The voltages on D11-D14 are off as follows (tuned to 40m, 14.1V power supply, low power TX is 0.1W, high power TX is 11W):
>
> D11:
>    * Anode:
>      * At low power, the anode seems fine in RX/TX.
>      * In high power, the RX voltage seems fine at about 1.7V, but in TX it is going up to 13.9V instead of of being around 1.6V.
>    * Cathode:
>      * In low power RX, it is 149V instead of 14.0V.  It dips slightly in TX.
>      * At high power RX, it is high at 136V instead of 14.0V.  TX voltage is also high at about 81V instead of 0.8V.
>
> D12:
>    * Anode:
>      * At low power, the anode seems fine in RX.  I am not seeing the dip in low power TX from 14.1V to 13.9V.
>      * In high power, the RX voltage seems fine at about 1.7V, but in TX it is going up to 13.9V instead of of being around 1.6V.
>    * Cathode:
>      * At low power, the RX voltae is a bit high, about 144V instead of 119V.  The voltage does dip slighltly in TX.
>      * In high power, the voltages seem roughly correct (0.9V RX/121V TX)
>
> D13:
>    * Anode:
>      * It seems fine at low power, staying at about 14.1V.
>      * At high power, it also seems fine, going up from about 1.7V RX to 14V TX.
>    * Cathode:
>      * At low power, the RX voltage is high at about 148V instead of 14.1V and dips slightly on TX.
>      * At high power, the RX voltage is high at about 136V instead of 14V.  At TX it drops to about 60V.
>
> D14:
>    * Anode:
>      * At low power, it seems fine at RX, 14.1V.  I am not seeing the TX dip.
>      * At high power, it also seems fine, going up from about 1.7V RX to 14V TX.
>    * Cathode:
>      * At low power, the voltages seem a touch high at 144V TX/143V RX instead of 117V/116V.
>      * At high power, the RX/TX voltages seem about right at 0.9V/120V.
>
> So, it seems to me there is an issue with biases on the T-R switch diodes.  I definitely hear a click when moving between high and low power modes, but I am not hearing anything on transmit.  I don’t know if I should.
>
>
> KAT-100 startup issue
> =====================
>
> This one isn’t as big of an issue, as I have a workaround.  When the KPA-100 was installed with the KAT-100 in the EC-2 enclosure, the KAt-100 never seemed to fully “boot” if the K2 was powered on with the power knob in the 0.1-10W range.  It would be stuck in a transmit-like state with the the antenna 1, SWR 1, and power range low LEDs lit.  Transmit wouldn’t work, and all of the LEDs on the K2’s power meter would also remain lit.  If the K2 is powered on with the power level set higher than 10W, then it seems to move past that point and enter normal operation.
>
>
> Thank you for taking the time to read through this.  I am a bit of a beginner, so it’s a bit of a challenge for me to diagnose and resolve these issues.
>
> 73,
>
> Daniel, AG5UT
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]