Re: [Elecraft] KPA runaway issue

[K8TE]

Joe,

Did you come to a solution to this problem?  I have the same issue with my
K3 #2 (not S) and accomplished all the possible fixes you did.

73, Bill, K8TE



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Re: [Elecraft] KPA runaway issue

[brian]

Hopefully AGC is not being used at all.
73 de Brian/K3KO

On 5/6/2017 23:46 PM, Nr4c wrote:

My KPA500 needs less than 20 watts on all bands.  Are you just driving it too 
hard?

Sent from my iPhone
...nr4c. bill



On May 6, 2017, at 3:01 PM, W1GO (Joe)  wrote:

All,

One additional factoid of interest … when in ESSB mode, the runaway issue 
doesn’t occur; only in standard bandwidth mode.  I’ve used standard bandwidth 
recently with out the KPA500 on and I’ve had no power out issues of poor audio 
reports.  Hence, it seems that somewhere after the K3 there are oscillations 
resulting (or at least only noticeable) from the narrower bandwidth signal.  
Interesting.

Take care, all.  If and when i figure it out I’ll share.  BTW, I did switch 
miss from a boom with foot pedal to a short cable desk mic just to rule that 
out.

Joe


On May 6, 2017, at 12:49 PM, W1GO (Joe)  wrote:


Elecraft faithful,

Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.

Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds 
of transmission / speech.  This seems to be independent of band.  With the KPA 
in standby, the K3 output power holds rock steady as indicated in the KPA.

Conditions:
-  Only about 20W of drive in SSB can result in the “redlining”  … To eliminate 
the redlining, I have to turn drive down to about 18W. … about 20W in CW 
provides about 500W fairly solid.
-  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
(14V to ~13.7V indicated on K3)
-  KPA is powered off 240 … I tried two different KPA transformer taps as I 
noticed with yellow tap the supply voltage right about 60V and occasionally a 
little below on key down.  Supply voltage stays well above 60V with red tap but 
same “redlining” of the KPA.
-  Have tried various mic gain compression settings using dynamic mikes.  
Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve gone 
as low as gain 15 / compression 15 (~5db) with no impact.
- I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
-  ALC on … ext ALC off …. varied these to see if there would be an impact.  
None.
-  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500


What I’ve tried / done:
-  Gain / compression changes as above
-  Checked K3 supply voltage and no significant voltage drop on key down
-  Changed power supply to a 35A powering K3 with no change
-  Varied KPA transformer taps t


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Re: [Elecraft] KPA runaway issue

[Don Wilhelm]

Joe,

That may be "no problem at all".  Unfortunately, you will not know that 
answer unless you can borrow a 'scope that can observe the RF input to 
the KPA500.


Some microphones and combinations of mic gain and compression may cause 
power output of the K3 to exceed the level obtained by a K3 keydown in CW.


Those peaks will cause the KPA500 output to go above the level obtained 
with CW.


Reduce the K3 power setting if you find that effect disconcerting.

73,
Don W3FPR

On 5/6/2017 12:49 PM, W1GO (Joe) wrote:


Elecraft faithful,

Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.

Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds 
of transmission / speech.  This seems to be independent of band.  With the KPA 
in standby, the K3 output power holds rock steady as indicated in the KPA.

Conditions:
-  Only about 20W of drive in SSB can result in the “redlining”  … To eliminate 
the redlining, I have to turn drive down to about 18W. … about 20W in CW 
provides about 500W fairly solid.
-  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
(14V to ~13.7V indicated on K3)
-  KPA is powered off 240 … I tried two different KPA transformer taps as I 
noticed with yellow tap the supply voltage right about 60V and occasionally a 
little below on key down.  Supply voltage stays well above 60V with red tap but 
same “redlining” of the KPA.
-  Have tried various mic gain compression settings using dynamic mikes.  
Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve gone 
as low as gain 15 / compression 15 (~5db) with no impact.

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Re: [Elecraft] KPA runaway issue

[Nr4c]

My KPA500 needs less than 20 watts on all bands.  Are you just driving it too 
hard?

Sent from my iPhone
...nr4c. bill


> On May 6, 2017, at 3:01 PM, W1GO (Joe)  wrote:
> 
> All,
> 
> One additional factoid of interest … when in ESSB mode, the runaway issue 
> doesn’t occur; only in standard bandwidth mode.  I’ve used standard bandwidth 
> recently with out the KPA500 on and I’ve had no power out issues of poor 
> audio reports.  Hence, it seems that somewhere after the K3 there are 
> oscillations resulting (or at least only noticeable) from the narrower 
> bandwidth signal.  Interesting.
> 
> Take care, all.  If and when i figure it out I’ll share.  BTW, I did switch 
> miss from a boom with foot pedal to a short cable desk mic just to rule that 
> out.
> 
> Joe
> 
>> On May 6, 2017, at 12:49 PM, W1GO (Joe)  wrote:
>> 
>> 
>> Elecraft faithful,
>> 
>> Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.
>> 
>> Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few 
>> seconds of transmission / speech.  This seems to be independent of band.  
>> With the KPA in standby, the K3 output power holds rock steady as indicated 
>> in the KPA.
>> 
>> Conditions:
>> -  Only about 20W of drive in SSB can result in the “redlining”  … To 
>> eliminate the redlining, I have to turn drive down to about 18W. … about 20W 
>> in CW provides about 500W fairly solid.
>> -  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
>> (14V to ~13.7V indicated on K3)
>> -  KPA is powered off 240 … I tried two different KPA transformer taps as I 
>> noticed with yellow tap the supply voltage right about 60V and occasionally 
>> a little below on key down.  Supply voltage stays well above 60V with red 
>> tap but same “redlining” of the KPA.
>> -  Have tried various mic gain compression settings using dynamic mikes.  
>> Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve 
>> gone as low as gain 15 / compression 15 (~5db) with no impact.
>> - I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
>> -  ALC on … ext ALC off …. varied these to see if there would be an impact.  
>> None.
>> -  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500
>> 
>> 
>> What I’ve tried / done:
>> -  Gain / compression changes as above
>> -  Checked K3 supply voltage and no significant voltage drop on key down
>> -  Changed power supply to a 35A powering K3 with no change 
>> -  Varied KPA transformer taps t

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Re: [Elecraft] KPA runaway issue

[W1GO (Joe)]

All,

One additional factoid of interest … when in ESSB mode, the runaway issue 
doesn’t occur; only in standard bandwidth mode.  I’ve used standard bandwidth 
recently with out the KPA500 on and I’ve had no power out issues of poor audio 
reports.  Hence, it seems that somewhere after the K3 there are oscillations 
resulting (or at least only noticeable) from the narrower bandwidth signal.  
Interesting.

Take care, all.  If and when i figure it out I’ll share.  BTW, I did switch 
miss from a boom with foot pedal to a short cable desk mic just to rule that 
out.

Joe

> On May 6, 2017, at 12:49 PM, W1GO (Joe)  wrote:
> 
> 
> Elecraft faithful,
> 
> Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.
> 
> Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds 
> of transmission / speech.  This seems to be independent of band.  With the 
> KPA in standby, the K3 output power holds rock steady as indicated in the KPA.
> 
> Conditions:
> -  Only about 20W of drive in SSB can result in the “redlining”  … To 
> eliminate the redlining, I have to turn drive down to about 18W. … about 20W 
> in CW provides about 500W fairly solid.
> -  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
> (14V to ~13.7V indicated on K3)
> -  KPA is powered off 240 … I tried two different KPA transformer taps as I 
> noticed with yellow tap the supply voltage right about 60V and occasionally a 
> little below on key down.  Supply voltage stays well above 60V with red tap 
> but same “redlining” of the KPA.
> -  Have tried various mic gain compression settings using dynamic mikes.  
> Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve gone 
> as low as gain 15 / compression 15 (~5db) with no impact.
> - I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
> -  ALC on … ext ALC off …. varied these to see if there would be an impact.  
> None.
> -  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500
> 
> 
> What I’ve tried / done:
> -  Gain / compression changes as above
> -  Checked K3 supply voltage and no significant voltage drop on key down
> -  Changed power supply to a 35A powering K3 with no change 
> -  Varied KPA transformer taps to ensure supply above 60V
> -  Changed coax between K3 and KPA and KPA and KAT500
> -  Tried with two different antennas / coax runs and had same result
> -  Varied TXG VCE from -1.5 to 1.5
> -  Performed gain calibration on K3
> 
> 
> 
> I’ve had the KPA for about 9 months but primarily operated CW so not sure if 
> this is a recent occurrence.  Any other suggestions would be appreciated.
> 
> Many thanks, all, and have a wonderful weekend.
> 
> 
> 
> Kindest regards,
> 
> Joe
> W1GO
> 
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Re: [Elecraft] KPA runaway issue

[Vic Rosenthal]

Just a guess, but if it happens in SSB but not CW, look for RF feedback into 
audio circuitry.

Vic 4X6GP 

> On 6 May 2017, at 19:49, W1GO (Joe)  wrote:
> 
> 
> Elecraft faithful,
> 
> Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.
> 
> Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds 
> of transmission / speech.  This seems to be independent of band.  With the 
> KPA in standby, the K3 output power holds rock steady as indicated in the KPA.
> 
> Conditions:
> -  Only about 20W of drive in SSB can result in the “redlining”  … To 
> eliminate the redlining, I have to turn drive down to about 18W. … about 20W 
> in CW provides about 500W fairly solid.
> -  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
> (14V to ~13.7V indicated on K3)
> -  KPA is powered off 240 … I tried two different KPA transformer taps as I 
> noticed with yellow tap the supply voltage right about 60V and occasionally a 
> little below on key down.  Supply voltage stays well above 60V with red tap 
> but same “redlining” of the KPA.
> -  Have tried various mic gain compression settings using dynamic mikes.  
> Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve gone 
> as low as gain 15 / compression 15 (~5db) with no impact.
> - I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
> -  ALC on … ext ALC off …. varied these to see if there would be an impact.  
> None.
> -  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500
> 
> 
> What I’ve tried / done:
> -  Gain / compression changes as above
> -  Checked K3 supply voltage and no significant voltage drop on key down
> -  Changed power supply to a 35A powering K3 with no change 
> -  Varied KPA transformer taps to ensure supply above 60V
> -  Changed coax between K3 and KPA and KPA and KAT500
> -  Tried with two different antennas / coax runs and had same result
> -  Varied TXG VCE from -1.5 to 1.5
> -  Performed gain calibration on K3
> 
> 
> 
> I’ve had the KPA for about 9 months but primarily operated CW so not sure if 
> this is a recent occurrence.  Any other suggestions would be appreciated.
> 
> Many thanks, all, and have a wonderful weekend.
> 
> 
> 
> Kindest regards,
> 
> Joe
> W1GO
> 
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Re: [Elecraft] KPA runaway issue

[W1GO (Joe)]

Guy,

Yes.  I did that.  I meant to say TX calibration below … I said gain 
calibration.

Thanks.

Joe

> On May 6, 2017, at 1:07 PM, Guy Olinger K2AV  wrote:
> 
> Run the 5 and 50 watt TX power calibration on the K3.  It's in the K3 utility 
> program. 
> 
> 73, Guy K2AV 
> 
> On Sat, May 6, 2017 at 12:51 PM W1GO (Joe)  > wrote:
> 
> Elecraft faithful,
> 
> Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.
> 
> Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds 
> of transmission / speech.  This seems to be independent of band.  With the 
> KPA in standby, the K3 output power holds rock steady as indicated in the KPA.
> 
> Conditions:
> -  Only about 20W of drive in SSB can result in the “redlining”  … To 
> eliminate the redlining, I have to turn drive down to about 18W. … about 20W 
> in CW provides about 500W fairly solid.
> -  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
> (14V to ~13.7V indicated on K3)
> -  KPA is powered off 240 … I tried two different KPA transformer taps as I 
> noticed with yellow tap the supply voltage right about 60V and occasionally a 
> little below on key down.  Supply voltage stays well above 60V with red tap 
> but same “redlining” of the KPA.
> -  Have tried various mic gain compression settings using dynamic mikes.  
> Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve gone 
> as low as gain 15 / compression 15 (~5db) with no impact.
> - I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
> -  ALC on … ext ALC off …. varied these to see if there would be an impact.  
> None.
> -  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500
> 
> 
> What I’ve tried / done:
> -  Gain / compression changes as above
> -  Checked K3 supply voltage and no significant voltage drop on key down
> -  Changed power supply to a 35A powering K3 with no change
> -  Varied KPA transformer taps to ensure supply above 60V
> -  Changed coax between K3 and KPA and KPA and KAT500
> -  Tried with two different antennas / coax runs and had same result
> -  Varied TXG VCE from -1.5 to 1.5
> -  Performed gain calibration on K3 (TX calibration) 
> 
> 
> 
> I’ve had the KPA for about 9 months but primarily operated CW so not sure if 
> this is a recent occurrence.  Any other suggestions would be appreciated.
> 
> Many thanks, all, and have a wonderful weekend.
> 
> 
> 
> Kindest regards,
> 
> Joe
> W1GO
> 
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Re: [Elecraft] KPA runaway issue

[Guy Olinger K2AV]

Run the 5 and 50 watt TX power calibration on the K3.  It's in the K3
utility program.

73, Guy K2AV

On Sat, May 6, 2017 at 12:51 PM W1GO (Joe)  wrote:

>
> Elecraft faithful,
>
> Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.
>
> Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few
> seconds of transmission / speech.  This seems to be independent of band.
> With the KPA in standby, the K3 output power holds rock steady as indicated
> in the KPA.
>
> Conditions:
> -  Only about 20W of drive in SSB can result in the “redlining”  … To
> eliminate the redlining, I have to turn drive down to about 18W. … about
> 20W in CW provides about 500W fairly solid.
> -  The K3 is powered by a 70A supply that does not sag much upon K3
> keydown (14V to ~13.7V indicated on K3)
> -  KPA is powered off 240 … I tried two different KPA transformer taps as
> I noticed with yellow tap the supply voltage right about 60V and
> occasionally a little below on key down.  Supply voltage stays well above
> 60V with red tap but same “redlining” of the KPA.
> -  Have tried various mic gain compression settings using dynamic mikes.
> Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve
> gone as low as gain 15 / compression 15 (~5db) with no impact.
> - I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
> -  ALC on … ext ALC off …. varied these to see if there would be an
> impact.  None.
> -  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500
>
>
> What I’ve tried / done:
> -  Gain / compression changes as above
> -  Checked K3 supply voltage and no significant voltage drop on key down
> -  Changed power supply to a 35A powering K3 with no change
> -  Varied KPA transformer taps to ensure supply above 60V
> -  Changed coax between K3 and KPA and KPA and KAT500
> -  Tried with two different antennas / coax runs and had same result
> -  Varied TXG VCE from -1.5 to 1.5
> -  Performed gain calibration on K3
>
>
>
> I’ve had the KPA for about 9 months but primarily operated CW so not sure
> if this is a recent occurrence.  Any other suggestions would be appreciated.
>
> Many thanks, all, and have a wonderful weekend.
>
>
>
> Kindest regards,
>
> Joe
> W1GO
>
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[Elecraft] KPA runaway issue

[W1GO (Joe)]

Elecraft faithful,

Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.

Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds 
of transmission / speech.  This seems to be independent of band.  With the KPA 
in standby, the K3 output power holds rock steady as indicated in the KPA.

Conditions:
-  Only about 20W of drive in SSB can result in the “redlining”  … To eliminate 
the redlining, I have to turn drive down to about 18W. … about 20W in CW 
provides about 500W fairly solid.
-  The K3 is powered by a 70A supply that does not sag much upon K3 keydown 
(14V to ~13.7V indicated on K3)
-  KPA is powered off 240 … I tried two different KPA transformer taps as I 
noticed with yellow tap the supply voltage right about 60V and occasionally a 
little below on key down.  Supply voltage stays well above 60V with red tap but 
same “redlining” of the KPA.
-  Have tried various mic gain compression settings using dynamic mikes.  
Without amp in-line I do fine with gain 30, compression 20 (10db).  I’ve gone 
as low as gain 15 / compression 15 (~5db) with no impact.
- I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact.
-  ALC on … ext ALC off …. varied these to see if there would be an impact.  
None.
-  SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500


What I’ve tried / done:
-  Gain / compression changes as above
-  Checked K3 supply voltage and no significant voltage drop on key down
-  Changed power supply to a 35A powering K3 with no change 
-  Varied KPA transformer taps to ensure supply above 60V
-  Changed coax between K3 and KPA and KPA and KAT500
-  Tried with two different antennas / coax runs and had same result
-  Varied TXG VCE from -1.5 to 1.5
-  Performed gain calibration on K3



I’ve had the KPA for about 9 months but primarily operated CW so not sure if 
this is a recent occurrence.  Any other suggestions would be appreciated.

Many thanks, all, and have a wonderful weekend.



Kindest regards,

Joe
W1GO

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