K1 Audio Problem after fitting KNB1 Noise Blanker

[Ray G3XLG]

Hi All

I've just completed the Noise Blanker to retrofit into existing my 4-band
K1, # 3020.

Part of the installation is to remove C22 from the K1 RF Board & fit the
female 8 pin connector at J1 which seemed to go OK.

I then fitted the KNB1 to the K1 & went through the initial tests. There was
immediately a fairly strong audio whine on all frequencies, all bands but
there were no error messages & the menu for the NB (Off/Hi/Lo) worked with
no problem.

The whine is present with/without an antenna connected and after removing
the NB board, the whine is now still present. CW signals can be tuned in
fine so the problem appears to be just in the audio.

Ant ideas please guys?

73

Ray, G3XLG

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[Don Wilhelm-4]

Ray,

Please describe the "whine" in more detail.  Is it more of a "popping"
noise, or is it a low ptched oscillation, or is it a high pitched
squeal, or something else.
Does it vary with the AF gain control or is it more constant - if it
varies, does it change in level, or pitch or both?
Does it vary when tuning through a strong signal - how about a weak one,
or is it present whether there is a signal being received or not.

If you do a TUNE (connect a dummy load first), is it silenced or is it
still present.

73,
Don W3FPR

On 1/10/2012 12:46 PM, Ray Spreadbury wrote:

> Hi All
>
> I've just completed the Noise Blanker to retrofit into existing my 4-band
> K1, # 3020.
>
> Part of the installation is to remove C22 from the K1 RF Board&  fit the
> female 8 pin connector at J1 which seemed to go OK.
>
> I then fitted the KNB1 to the K1&  went through the initial tests. There was
> immediately a fairly strong audio whine on all frequencies, all bands but
> there were no error messages&  the menu for the NB (Off/Hi/Lo) worked with
> no problem.
>
> The whine is present with/without an antenna connected and after removing
> the NB board, the whine is now still present. CW signals can be tuned in
> fine so the problem appears to be just in the audio.
>
> Ant ideas please guys?
>
> 73
>
> Ray, G3XLG
>

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[Ray G3XLG]

Hi Don
The "whine" is a steady continuous tone (perhaps at 800 or 900 cycles), not
popping, nor a low pitched oscillation and in fact I wondered if the
sidetone spot was on or if the key was down.
It does vary in level with the AF gain control but doesn't change in pitch.
It is present whether there is a signal being received or not. It is still
present if I do a tune.

73
Ray G3XLG

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: 10 January 2012 20:35
To: Ray Spreadbury
Cc: [hidden email]
Subject: Re: [Elecraft] K1 Audio Problem after fitting KNB1 Noise Blanker

Ray,

Please describe the "whine" in more detail.  Is it more of a "popping"
noise, or is it a low ptched oscillation, or is it a high pitched
squeal, or something else.
Does it vary with the AF gain control or is it more constant - if it
varies, does it change in level, or pitch or both?
Does it vary when tuning through a strong signal - how about a weak one,
or is it present whether there is a signal being received or not.

If you do a TUNE (connect a dummy load first), is it silenced or is it
still present.

73,
Don W3FPR



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[Don Wilhelm-4]

Ray,

OK since the tone dd not stop during a TUNE, that places the problem
after transistor Q10.  Refer to the schematic for the RF board sheet 1
in the lower left corner - everything there is suspect.
You should be able to short U4 pin 3 to ground and kill the sound - if
that is true, the problem is with the U3, Q10 or Q11 stages and their
associated components.  If shorting U4 pin 3 to ground does not stop it,
it is a problem with U4 and its components.

Be aware that a leaky capacitor (in conjunction with a resistor) can
create an unintended oscillator.  Replacement of capacitors may be in
order - but unfortunately, I cannot tell you which ones.

As a bit of history -- at one time, the KX1 0.1 uF capacitors were a
problem (problem now fixed), but the 0.1 uF capacitors in the K1 are not
the same - however, if you substituted a blue body 0.1 inch lead spacing
capacitor for a 0.1 uF capacitor used for the K1, then that is suspect.

"Tis a mystery right now - let's hope it can be found in short order.

I would re-flow the soldering at U3 and U4 just to see if a soldering
problem is the cause.  I suspect it is - and your opening the K1 to
install the KNB1 just accelerated an impending failure point.

73,
Don W3FPR



On 1/10/2012 4:52 PM, Ray Spreadbury wrote:

> Hi Don
> The "whine" is a steady continuous tone (perhaps at 800 or 900 cycles), not
> popping, nor a low pitched oscillation and in fact I wondered if the
> sidetone spot was on or if the key was down.
> It does vary in level with the AF gain control but doesn't change in pitch.
> It is present whether there is a signal being received or not. It is still
> present if I do a tune.
>
> 73
> Ray G3XLG
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: 10 January 2012 20:35
> To: Ray Spreadbury
> Cc: [hidden email]
> Subject: Re: [Elecraft] K1 Audio Problem after fitting KNB1 Noise Blanker
>
> Ray,
>
> Please describe the "whine" in more detail.  Is it more of a "popping"
> noise, or is it a low ptched oscillation, or is it a high pitched
> squeal, or something else.
> Does it vary with the AF gain control or is it more constant - if it
> varies, does it change in level, or pitch or both?
> Does it vary when tuning through a strong signal - how about a weak one,
> or is it present whether there is a signal being received or not.
>
> If you do a TUNE (connect a dummy load first), is it silenced or is it
> still present.
>
> 73,
> Don W3FPR
>
>
>
> ______________________________________________________________
> 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
>

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[Mike Morrow-3]

Ray wrote:

> The "whine" is a steady continuous tone (perhaps at 800 or 900 cycles), not
> popping, nor a low pitched oscillation and in fact I wondered if the
> sidetone spot was on or if the key was down.

Have you checked that the small slide switch S2 for for the OFFSET TEST adjustment
(on bottom of the RF board) didn't get inadvertently placed in the TEST position
rather than the OPER position?

I'd check that before anything else.

73,
Mike / KK5F
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[Ray G3XLG]

Thank you Don & Mike for your suggestions!
Yes, I had somehow accidentally moved S2 into the TEST position when removing C2.
Putting it back into the OPER position cured the problem
I feel a bit of a fool but thanks both for helping out
73
Ray, G3XLG

-----Original Message-----
From: Mike Morrow [mailto:[hidden email]]
Sent: 11 January 2012 02:11
To: Ray Spreadbury; [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] K1 Audio Problem after fitting KNB1 Noise Blanker

Ray wrote:

> The "whine" is a steady continuous tone (perhaps at 800 or 900 cycles), not
> popping, nor a low pitched oscillation and in fact I wondered if the
> sidetone spot was on or if the key was down.

Have you checked that the small slide switch S2 for for the OFFSET TEST adjustment
(on bottom of the RF board) didn't get inadvertently placed in the TEST position
rather than the OPER position?

I'd check that before anything else.

73,
Mike / KK5F

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