KPA500: How to troubleshoot "distorted audio"

[Jim Hooper]

Hmph.    

My 3 month old KPA500 with my K3 and KAT500 had been giving me “outstanding audio” reports when first put into service.    

But something changed and I don’t know what.  

I am now getting distorted audio when I turn it to operate from standby.    Could not use it for my casual participation in the 7QP QSO party this weekend, and that was disappointing.  

Suggestions on how to troubleshoot?    

73,
Hoop
K9QJS
San Juan Island, WA
______________________________________________________________
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]

[mcduffie]

> My 3 month old KPA500 with my K3 and KAT500 had been giving me “outstanding audioâ€? reports when first put into service.

I'd bet it doesn't sound bad on a dummy load?

Gary
______________________________________________________________
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]

[Jack Brindle-2]

Jim;

Gary is right. What he means to tell you is that you should be looking for RF in the shack, getting into the K3.

If the KPA500 had gone non-linear, then you would be seeing all sorts of faults. You aren’t reporting any, so
most likely the problem is not in the KPA, but rather in something that cannot deal with the large amount of RF in the vicinity.
Did you change something recently, antenna, audio, cabling, something else in the shack?

- Jack Brindle, W6FB
Elecraft Engineering

> On May 3, 2015, at 3:21 PM, [hidden email] wrote:
>
>
>> My 3 month old KPA500 with my K3 and KAT500 had been giving me “outstanding audioâ€? reports when first put into service.
>
> I'd bet it doesn't sound bad on a dummy load?
>
> Gary
> ______________________________________________________________
> 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]

______________________________________________________________
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]

[Jim Hooper]

Jack and all,

Testing tomorrow will include testing on a dummy load.

Yesterday I did experience faults on the KPA500 - several and then I stopped using it.  

Hoop




On May 3, 2015, at 16:01 , Jack Brindle <[hidden email]> wrote:

Jim;

Gary is right. What he means to tell you is that you should be looking for RF in the shack, getting into the K3.

If the KPA500 had gone non-linear, then you would be seeing all sorts of faults. You aren’t reporting any, so
most likely the problem is not in the KPA, but rather in something that cannot deal with the large amount of RF in the vicinity.
Did you change something recently, antenna, audio, cabling, something else in the shack?

- Jack Brindle, W6FB
Elecraft Engineering

> On May 3, 2015, at 3:21 PM, [hidden email] wrote:
>
>
>> My 3 month old KPA500 with my K3 and KAT500 had been giving me “outstanding audioâ€? reports when first put into service.
>
> I'd bet it doesn't sound bad on a dummy load?
>
> Gary
> ______________________________________________________________
> 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]

______________________________________________________________
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]

[Matt Zilmer-2]

Check your RF ground.

On Sun, 03 May 2015 16:01:36 -0700, you wrote:

>Jim;
>
>Gary is right. What he means to tell you is that you should be looking for RF in the shack, getting into the K3.
>
>If the KPA500 had gone non-linear, then you would be seeing all sorts of faults. You aren’t reporting any, so
>most likely the problem is not in the KPA, but rather in something that cannot deal with the large amount of RF in the vicinity.
>Did you change something recently, antenna, audio, cabling, something else in the shack?
>
>- Jack Brindle, W6FB
>Elecraft Engineering
>
>> On May 3, 2015, at 3:21 PM, [hidden email] wrote:
>>
>>
>>> My 3 month old KPA500 with my K3 and KAT500 had been giving me â??outstanding audioâ?? reports when first put into service.
>>
>> I'd bet it doesn't sound bad on a dummy load?
>>
>> Gary
>> ______________________________________________________________
>> 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]
>
>______________________________________________________________
>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]

Matt Zilmer, W6NIA
www.elecraft.com
831-763-4211  x129


______________________________________________________________
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]

[Jim Brown-10]

On Sun,5/3/2015 10:21 PM, Matt Zilmer wrote:
> Check your RF ground.

WRONG! A connection to mother earth has nothing to do with solving RFI
issues, nor does it make antennas work better.

RATHER -- check BONDING and SHIELD connections -- is there a coax with a
bad shield connection? Is every equipment chassis in the station bonded
to every other chassis? That includes computer, rig, power amp, other
accessories, the PSU for the rig. Is there a bond from there to power
system "ground?"

Since this is a problem that was not there before and is now, look for
things that could have failed or changed. If it were not for that, I
would be suggesting common mode chokes at the feedpoint of the antenna
in use.

When it worked before and doesn't work now, always ask "what might have
changed (broken)?"

73, Jim K9YC
______________________________________________________________
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]

[Ignacy]

Aside from RF feedback it may be low no-signal current. Had it in K3.
Ignacy, NO9E

[Jim Hooper]

Thanks again to everyone who responded to my question about troubleshooting distorted audio on my K-Line.

This note is to provide you feedback on what I believe to be the causal factor for the distorted audio.  

The distorted audio goes away when I remove the line-in stereo cable (a Radio Shack cable) that goes from my MBox-2 sound “card” to the K3; the MBox-2 does not need to be connected by USB to my computer for there to be audio distortion.    

I have had an MBox-2 for over 10 years and have used it for voice recording to ProTools software, though I have haven’t used it for that application for quite awhile.   Having the MBox2 available and having read Jim’s write-ups on sound cards, I thought I would give it a try fairly recently - this it the answer to the question “what changed” that led to the audio distortion.   I removed my SignaLink and inserted the MBox-2.  

I am much relieved to have found the problem.   I will need to do more research to ascertain whether the stereo audio cable or the MBox-2, in this application, is the problem area.

At the same time, I will quickly say that I have also identified that I need to implement station bonding improvements.  

But having identified the problem and my being able to eliminate it is quite a relief.    

Again, thank you to all those of you who responded, and especially to Jim and to Jack.      

73,
Hoop
K9QJS
San Juan Island, WA
______________________________________________________________
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]