Elecraft

Problem: K2 Audio Tuning Click or Warble

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Bill Acito W1PA

Problem: K2 Audio Tuning Click or Warble

After a few months of relative inactivity, I went back last night to
continue building my KPA100,
and had the K2 on in the background. I actually thought it was a DSP
artifact, but it's there even with the DSP in bypass.

Tuning through a quiet band, I noticed as I tuned slowly across a CW signal,
I could clearly hear some "artifact" chirps or warbles with each increment
of the dial (even at the finest tuning rate). There are other references to
this in the archive:

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00110.html

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00134.html

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00121.html

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00420.html

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00424.html

This is K2 #61, one of the original field tester units, and it has had all
upgrade mods (at least I am pretty sure it has). I captured a .wma of it to
hear for yourself:

http://webpages.charter.net/acito/w1pa/

Suggestions?

Bill W1PA
K2 #61

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Darwin, Keith

RE: Problem: K2 Audio Tuning Click or Warble

Nice recording. Mine definitely does NOT do that. I wish I could be
more help.

- Keith KD1E -
- K2 5411 -

-----Original Message-----
From: Bill Acito W1PA

Tuning through a quiet band, I noticed as I tuned slowly across a CW
signal, I could clearly hear some "artifact" chirps or warbles with each
increment of the dial (even at the finest tuning rate).

This is K2 #61, one of the original field tester units, and it has had
all upgrade mods (at least I am pretty sure it has). I captured a .wma
of it to hear for yourself:

http://webpages.charter.net/acito/w1pa/

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w1xt

Re: Problem: K2 Audio Tuning Click or Warble

In reply to this post by Bill Acito W1PA

Hi Bill,

You're not completely alone! Mine does that to a much, much lesser degree.
Noticeable as a slight warble as one tunes through a signal slowly.

My s/n is 1434 with most if not all upgrades. Firmware is current.

I'm planning to buy a new K2 in the next day or so -- one of the reasons is
to see if the problem is gone!

Anyone posting responses to Bill's questions, please be sure they are posted
here too.

Thanks,

Bob W1XT
Surprise, AZ

----- Original Message -----
From: "Bill Acito W1PA" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, October 11, 2006 7:44 AM
Subject: [Elecraft] Problem: K2 Audio Tuning Click or Warble

> After a few months of relative inactivity, I went back last night to
> continue building my KPA100,
> and had the K2 on in the background. I actually thought it was a DSP
> artifact, but it's there even with the DSP in bypass.
>
> Tuning through a quiet band, I noticed as I tuned slowly across a CW
> signal, I could clearly hear some "artifact" chirps or warbles with each
> increment of the dial (even at the finest tuning rate). There are other
> references to this in the archive:
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00110.html
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00134.html
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-10/msg00121.html
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00420.html
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00424.html
>
> This is K2 #61, one of the original field tester units, and it has had all
> upgrade mods (at least I am pretty sure it has). I captured a .wma of it
> to hear for yourself:
>
> http://webpages.charter.net/acito/w1pa/
>
>
>
> Suggestions?
>
> Bill W1PA
> K2 #61
>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>

Geoffrey Mackenzie-Kennedy-2

Re: Problem: K2 Audio Tuning Click or Warble

In reply to this post by Bill Acito W1PA

Bill W1PA wrote:

---------------------------------------------------------------

Very occasionally have I noticed something similar, but like Bill W1XT to a
much lesser degree. I have heard it on 40m and 15m but only after the K2 has
been.switched off for a few days. It occurs once every time the tuning knob
is rotated 360 degrees (slow rate tuning), but only during 5 or 6 turns and
has appeared at different frequencies in the bands. A 'thump' test does not
get rid of it. When and if it does appear after the K2 has been off for a
few days, it disappears after the rig has been on for an hour or so.

73,
Geoff
GM4ESD

K2/100 #3255 Firmware Rev 2.04

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Bill Acito W1PA

Re: Problem: K2 Audio Tuning Click or Warble

In reply to this post by Bill Acito W1PA

Update.

1. Tom (N0SS) suggested I redo the CAL PLL. Done. No effect.

2. Jim (K4ZM) suggested I....

> Check the resistance of the small 100uh rfc that you added between 16 and
> the +12 volt line. I have seen this same problem when that RCF is open.
> It is a very delicate choke and very easy to break the wire inside the
> choke. An easy way to test it is to measure the dc voltage on both sides
> of the rfc and if the voltage is not the same then you probably have a bad
> RFC.

..so I popped the bottom and took a look. On the rail (which is not 12v,
btw), I read 5.02V,
and on the other side of the 100uH I read 4.23V... not the "same", but I
assume that's the
choke wire resistance. Along the same vein, I also remembered that someone
else attributed
this issue to the added LC circuit (as part of the A-B version update):

http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00424.html

So I took the blade of my screwdriver and shorted the 100uH inductor
(RFC15).... warble is gone!

So, questions:

Are the L-C comps "hard-linked"? i.e. if I remove this mod, is there any
benefit to leaving the cap,
or should I remove both parts? Should I try a different 100uH instead? I
don't think I ever had the
7128 warble, so I installed these as a precaution only.

Any ideas on why this LC circuit is the culprit (might want to look at this
since there is at least two confirmed cases now)?

As Wayne suggested in the included link, I also checked the value of R19 and
it was fine.

Bill
W1PA

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Brian Broggie-2

Re: Problem: K2 Audio Tuning Click or Warble

Sounds to me like that pretty fragile RFC15 (E690013) has opened. Scott
([hidden email]) can get you a new one right away.

Brian, W6FVI

Bill Acito W1PA wrote:

> Update.
>
> 1. Tom (N0SS) suggested I redo the CAL PLL. Done. No effect.
>
> 2. Jim (K4ZM) suggested I....
>
>> Check the resistance of the small 100uh rfc that you added between 16
>> and the +12 volt line. I have seen this same problem when that RCF
>> is open. It is a very delicate choke and very easy to break the wire
>> inside the choke. An easy way to test it is to measure the dc voltage
>> on both sides of the rfc and if the voltage is not the same then you
>> probably have a bad RFC.
>
>
> ..so I popped the bottom and took a look. On the rail (which is not
> 12v, btw), I read 5.02V,
> and on the other side of the 100uH I read 4.23V... not the "same",
> but I assume that's the
> choke wire resistance. Along the same vein, I also remembered that
> someone else attributed
> this issue to the added LC circuit (as part of the A-B version update):
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00424.html
>
> So I took the blade of my screwdriver and shorted the 100uH inductor
> (RFC15).... warble is gone!
>
> So, questions:
>
> Are the L-C comps "hard-linked"? i.e. if I remove this mod, is there
> any benefit to leaving the cap,
> or should I remove both parts? Should I try a different 100uH instead?
> I don't think I ever had the
> 7128 warble, so I installed these as a precaution only.
>
> Any ideas on why this LC circuit is the culprit (might want to look at
> this since there is at least two confirmed cases now)?
>
> As Wayne suggested in the included link, I also checked the value of
> R19 and it was fine.
>
> Bill
> W1PA
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>

Bill Acito W1PA

Re: Problem: K2 Audio Tuning Click or Warble

RFC15 supplies the 5V to the VDD pin of the MC14570... how can there be
4.23V at the pin if RFC15 is open and there is no other VDD pin on the IC?

Bill
W1PA

----- Original Message -----
From: "w6fvi" <[hidden email]>
To: "Bill Acito W1PA" <[hidden email]>
Cc: <[hidden email]>
Sent: Thursday, October 12, 2006 11:55 AM
Subject: Re: [Elecraft] Problem: K2 Audio Tuning Click or Warble

> Sounds to me like that pretty fragile RFC15 (E690013) has opened. Scott
> ([hidden email]) can get you a new one right away.
>
> Brian, W6FVI
>

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Don Wilhelm-3

RE: Problem: K2 Audio Tuning Click or Warble

In reply to this post by Bill Acito W1PA

Bill,

I would wager that the choke is actually open. This is one place where you
cannot readily detect an open choke by measuring the voltage on each side of
it. Turn power off and measure the resistance, and I believe you will see
that it is open.

If you have another 100 uH choke that will fit, just replace it. Even
Elecraft has switched to a larger choke I believe just because many folks
have damaged the tiny one when bending the leads. If you do not have a 100
uH choke available, temporarily jumper across it until you can obtain a
replacement choke.

73,
Don W3FPR

> -----Original Message-----
>
> Update.
>
> 1. Tom (N0SS) suggested I redo the CAL PLL. Done. No effect.
>
> 2. Jim (K4ZM) suggested I....
>
> > Check the resistance of the small 100uh rfc that you added
> between 16 and
> > the +12 volt line. I have seen this same problem when that RCF
> is open.
> > It is a very delicate choke and very easy to break the wire inside the
> > choke. An easy way to test it is to measure the dc voltage on
> both sides
> > of the rfc and if the voltage is not the same then you probably
> have a bad
> > RFC.
>
> ..so I popped the bottom and took a look. On the rail (which is not 12v,
> btw), I read 5.02V,
> and on the other side of the 100uH I read 4.23V... not the "same", but I
> assume that's the
> choke wire resistance. Along the same vein, I also remembered
> that someone
> else attributed
> this issue to the added LC circuit (as part of the A-B version update):
>
> http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-08/msg00424.html
>
> So I took the blade of my screwdriver and shorted the 100uH inductor
> (RFC15).... warble is gone!
>
> So, questions:
>
> Are the L-C comps "hard-linked"? i.e. if I remove this mod, is there any
> benefit to leaving the cap,
> or should I remove both parts? Should I try a different 100uH instead? I
> don't think I ever had the
> 7128 warble, so I installed these as a precaution only.
>
> Any ideas on why this LC circuit is the culprit (might want to
> look at this
> since there is at least two confirmed cases now)?
>
> As Wayne suggested in the included link, I also checked the value
> of R19 and
> it was fine.
>
> Bill
> W1PA
>

Bill Acito W1PA

Re: Problem: K2 Audio Tuning Click or Warble

In reply to this post by Bill Acito W1PA

>
> RFC15 supplies the 5V to the VDD pin of the MC14570... how can there be
> 4.23V at the pin if RFC15 is open and there is no other VDD pin on the IC?
>

I'll answer my own question: apparently, very easily.

Power-off DC resistance check confirmed that the RFC15 was open. No visual
indication of
any problem with it when examined. I had a larger, green version of the
100uH left
over from another mod, so I replaced it and low-and-behold, no warble.
Someone
mentioned to me that later versions of the K2 have the sturdier part -- I
hope so.

The MC14570 must have been getting DC from the inputs in lieu of no DC at
VDD, hence
the near-5V reading.

A ham and builder for 25+ years, and worked in semiconductor manufacturing
for 10+ years,
and still things to learn.

Thanks all for the help. Can I have some catsup for my crow, please?

Bill
W1PA

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Bill Johnson-10

RE: Problem: K2 Audio Tuning Click or Warble

In reply to this post by w1xt

I have units listed below and the # 35 SN with most all upgrades does not
have the problem. Buying a new one and building it will not resolve the
issue with the old. The techs on this list can help you or you can send it
in for a complete checkup and fix if you are ready to through in the towel.

Bill
K9YEQ

K2-35 & 5279; KX1-35/3080
___________________________________

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Wednesday, October 11, 2006 5:27 PM
To: [hidden email]
Subject: Re: [Elecraft] Problem: K2 Audio Tuning Click or Warble

Hi Bill,

You're not completely alone! Mine does that to a much, much lesser degree.
Noticeable as a slight warble as one tunes through a signal slowly.

My s/n is 1434 with most if not all upgrades. Firmware is current.

I'm planning to buy a new K2 in the next day or so -- one of the reasons is
to see if the problem is gone!

Anyone posting responses to Bill's questions, please be sure they are posted
here too.

Thanks,

Bob W1XT
Surprise, AZ

----- Original Message -----
From: "Bill Acito W1PA" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, October 11, 2006 7:44 AM
Subject: [Elecraft] Problem: K2 Audio Tuning Click or Warble

> upgrade mods (at least I am pretty sure it has). I captured a .wma of it
> to hear for yourself:
>
> http://webpages.charter.net/acito/w1pa/
>
>
>
> Suggestions?
>
> Bill W1PA
> K2 #61
>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>

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