Raspy Audio

[Steve & Anne Ray]

I have run into the first problem with my K2 S/N 1422, which has the latest
firmware and mods.   I built it back in 2000 and not had any problems with
it till a few weeks ago.  It now has an intermittent problem of receiving
and transmitting a very raspy audio.   It is not caused by AC magnetic
coupling as I have no magnetic transformers near it.      When the problem
occurs it will be on all bands and switching bands shows it is probably in
the pll.   A good sharp wack on the case will make it disappear, so it
appears to be a poor solder connection.   Needless to say when I open it up
and try and duplicate the problem by tapping on various components I cannot
make it occur.   I have reheated all the connections around the pll
circuitry, with no success.   The really aggravation is that this problem
will not show up for weeks and then start reoccurring.  Any ideas?

 

73,

Steve K4JPN

 

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[Bill K9YEQ]

Ouch, that hurts.  Don, will probably have a solution.  Just wanted to get
to you ASAP with an idea.

Bill
K9YEQ


-----Original Message-----
From: Steve & Anne Ray [mailto:[hidden email]]
Sent: Monday, March 22, 2010 4:16 PM
To: 'Bill K9YEQ'
Subject: RE: [Elecraft] Raspy Audio

No this is both on cw receive and transmit, thanks for the idea.


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[Don Wilhelm-4]

Steve,

Based on your "sharp whack" cure, but yes, that does usually indicate a
solder problem (or something loose).
I would first check RFC15 on the bottom of the board - it is connected
to pin 16 of U4 - check it with an ohmeter, even if it is open, it will
measure 5 volts on both ends.  Since your problem is intermittent, I
could suppose that RFC15 is damaged, but not completely.  If you suspect
that at all, jumper it out temporarily and see if the problem ceases to
occur.

Other things that can contribute to raspy TX audio are the KPA100 ribbon
cable and its speaker cable.  If this is a KPA100, be certain those are
dressed as far away from the KSB2 board as possible.  Remove the right
side panel and tuck these cables up into the corner between the KPA100
front cover panel and the top of the control board.

If neither of those steps correct the problem, it could be something
following the PLL itself.  Look at the schematic for the RF Board sheet
1 - everything to the right of U4 is a potential suspect and could
deserve re-flowing the solder.

73,
Don W3FPR

Steve & Anne Ray wrote:

> I have run into the first problem with my K2 S/N 1422, which has the latest
> firmware and mods.   I built it back in 2000 and not had any problems with
> it till a few weeks ago.  It now has an intermittent problem of receiving
> and transmitting a very raspy audio.   It is not caused by AC magnetic
> coupling as I have no magnetic transformers near it.      When the problem
> occurs it will be on all bands and switching bands shows it is probably in
> the pll.   A good sharp wack on the case will make it disappear, so it
> appears to be a poor solder connection.   Needless to say when I open it up
> and try and duplicate the problem by tapping on various components I cannot
> make it occur.   I have reheated all the connections around the pll
> circuitry, with no success.   The really aggravation is that this problem
> will not show up for weeks and then start reoccurring.  Any ideas?
>
>  
>
> 73,
>
> Steve K4JPN
>
>  
>
> ______________________________________________________________
> Elecraft mailing list
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>
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>  

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[Geoffrey Mackenzie-Kennedy]

Steve,

Another cause of intermittent raspy audio during both transmit and receive
could be a dicey solder joint in the KSB2's crystal filter circuit. If one
of the bandwidth settings you have chosen for the variable bandwidth crystal
filter is 1.8 kHz or wider, try switching to this filter setting during
receive to see if the rasp disappears.

73,
Geoff
GM4ESD


Steve & Anne Ray wrote on 03/22/2010 :

>I have run into the first problem with my K2 S/N 1422, which has the latest
> firmware and mods.   I built it back in 2000 and not had any problems with
> it till a few weeks ago.  It now has an intermittent problem of receiving
> and transmitting a very raspy audio.

<snip>


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