[Elecraft] K3 speaker audio gone!

Tue Aug 28 15:35:56 EDT 2012

Iain,

The mod you referenced below is a very old one (470 ohm resistors on  
the KIO3). It has been in production for a long time.

The mod I was talking about is newer (2010, I believe). It involves a  
pair of very small-valued resistors in series with the AF output  
coupling capacitors. This, too, is in production.

However, I just looked on the K3 mods page, and it appears that we  
never did turn this into a mod kit. We'll get this corrected right away.

Wayne
N6KR

On Aug 28, 2012, at 12:17 PM, iain macdonnell - N6ML wrote:

> See: http://www.elecraft.com/K3/mods/AF_Output_Mod_Rev_C.pdf
>
> "This modification is needed for all K3s shipped to date containing
> either a Revision XB or Revision A KIO3
> board. You must inspect the KIO3 board to see whether the modification
> has been made. Modified boards will
> include the leaded resistors shown in Figure 4. You can see the
> resistor in the lower part of the figure by removing
> the top cover as shown in Figure 1 and inspecting the side of the KIO3
> board facing away from the rear panel.  "
>
> Also http://www.elecraft.com/K3/k3_app_notes.htm states "Included on
> all new K3s About 12/23/08 and later."
>
> 73,
>
>    ~iain / N6ML
>
>
> On Tue, Aug 28, 2012 at 11:31 AM, hawley, charles j jr
> <c-hawley at illinois.edu> wrote:
>> Was there a serial # that included the current limiting?
>>
>> Sent from my iPhone
>>
>> On Aug 28, 2012, at 1:18 PM, "Wayne Burdick" <n6kr at elecraft.com>  
>> wrote:
>>
>>> Dave,
>>>
>>> Do you have the AF amp current-limiting mod in place? The parts for
>>> this mod are installed on the RF board. They've been in production  
>>> for
>>> quite some time, and we can send them to you on request.
>>>
>>> With the limiter installed, we've seen near-zero problems with the  
>>> AF
>>> amp IC.
>>>
>>> 73,
>>> Wayne
>>> N6KR
>>>
>>>
>>>
>>> On Aug 28, 2012, at 10:25 AM, Dave Hachadorian wrote:
>>>
>>>> I have blown the speaker amp twice, in two different radios, by
>>>> using a speaker with AGC OFF.  POOF! Gone before you can react by
>>>> turning down the audio.
>>>>
>>>> The factory guys report that they have been unable to duplicate
>>>> the problem.  Unless you are an EXPERT solderer, replacing the
>>>> speaker amp chip is best done by the factory.  The job will run
>>>> about $125 with shipping, maybe a little less if you ship only
>>>> the DSP Board.  I don't use the speaker amp any more.  I still
>>>> think there is a transient susceptibility problem in that
>>>> circuitry that they have been unable to find.
>>>>
>>>>
>>>> Dave Hachadorian, K6LL
>>>> Big Bear Lake, California
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Mike Goldstein
>>>> Sent: Tuesday, August 28, 2012 9:07 AM
>>>> To: elecraft at mailman.qth.net
>>>> Subject: [Elecraft] K3 speaker audio gone!
>>>>
>>>>       I've lost audio from both the internal speaker in the
>>>> K3,
>>>> and from the SPKRS output jack on the rear panel.
>>>>
>>>>       At the end of the the first week of using a new NESCAF
>>>> audio
>>>> filter (which drives my speaker) with the K3,  I changed bands,
>>>> listened briefly on CW, with the NESCAF filter in the circuit.  I
>>>> then changed to SSB, and because the NESCAF filter was adjusted
>>>> for a
>>>> very narrow audio bandwidth, I decided to switch it out of the
>>>> circuit, while the K3 was delivering audio, at a comfortable
>>>> listening level..
>>>>
>>>>       The audio filter was driven from the SPKRS jack on the
>>>> back
>>>> of the K3, using a stereo plug, with one channel floating.  The
>>>> SPKRS
>>>> jack was CONFIGured as SPKRS = 1.
>>>>
>>>> A front panel toggle switch on the filter panel turns off the
>>>> power
>>>> to the NESCAF filter, and re-routes the speaker audio connection
>>>> from
>>>> the filter output, to the K3 output directly. I had done this
>>>> often,
>>>> for the first week of operations.
>>>>
>>>> This time, however, I briefly saw a "HI CURR" indication on the
>>>> front
>>>> panel of the K3, and then my speaker audio vanished.
>>>>
>>>> Unplugging all connections from the rear panel SPKRS jack, and
>>>> the
>>>> front panel PHONES jack, no longer allows the K3's internal
>>>> speaker
>>>> to produce audio.  Nothing I tried would result in any audio from
>>>> the
>>>> external speaker, after connecting that speaker to either of the
>>>> phono jacks that were tied to the rear SPKRS jack, through the
>>>> stereo plug.
>>>>
>>>> The INPUT jack on the SCAF filter (to which the K3's SPKRS jack
>>>> was
>>>> connected) passes through an isolating capacitor, then a 27K
>>>> resistor, before being connected to the chip in the audio filter.
>>>>
>>>> Resetting SPRKS = 2, in the  CONFIG menu, had no effect on
>>>> producing
>>>> audio in the external, or internal speaker.
>>>>
>>>> I still have audio  at the PHONES jack on the front panel, so I
>>>> can
>>>> still use the K3.  It subsequently accounted for 380 QSOs in the
>>>> NAQP
>>>> CW contest, providing it usual flawless performance.
>>>>
>>>> I still have audio at the PHONES jack on the rear panel, as well.
>>>>
>>>> My theory (and Gary at Elecraft Service agrees it might be the
>>>> cause)
>>>> is that the audio chip in the K3 didn't like the abrupt change of
>>>> load impedance, from 27K (approx.) to infinity, to 8 ohms, while
>>>> it
>>>> was delivering audio..
>>>>
>>>> I've since soldered a 15K resistor across the input jack of the
>>>> audio
>>>> filter, and will do likewise for any other audio filters I
>>>> encounter, and use.
>>>>
>>>> Puzzling, huh?  73 de  VE3GFN
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:Elecraft at mailman.qth.net
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list:
>>>> http://www.qsl.net/donate.html
>>>>
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:Elecraft at mailman.qth.net
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Elecraft at mailman.qth.net
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html