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K3 speaker amp chip bites the dust again

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Dave Hachadorian-2

K3 speaker amp chip bites the dust again

I guess I've blown the speaker amp IC in my K3 again. This is
the third time this has happened, twice in one radio and once in
another.

In this case, the radio had both the AF Output Mod Kit (pair of
470 ohm resistors) and the E85056 Audio Protection Assembly
Circuit Board installed.

I was operating on Field Day, with headphones, as I usually do,
when some onlookers wanted to hear what was going on. I flipped
SPKRS+PHONES=YES, then along came a strong signal, and poof! no
speaker audio.

AGC SLP was zero, and AGC THR was 020. Front panel AGC was FAST.

This failure is really getting old, especially at $120 a pop to
get it fixed.

Dave Hachadorian, K6LL
Big Bear Lake, CA

.

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Fred Townsend-2

Re: K3 speaker amp chip bites the dust again

It sounds like there may be another fault in your system. Are you hooking up to any powered external speakers or phones?
73, Fred, AE6QL

-----Original Message-----

>From: Dave Hachadorian <[hidden email]>
>Sent: Jul 1, 2014 12:28 PM
>To: Reflector Elecraft <[hidden email]>
>Subject: [Elecraft] K3 speaker amp chip bites the dust again
>
>I guess I've blown the speaker amp IC in my K3 again. This is
>the third time this has happened, twice in one radio and once in
>another.
>
>In this case, the radio had both the AF Output Mod Kit (pair of
>470 ohm resistors) and the E85056 Audio Protection Assembly
>Circuit Board installed.
>
>I was operating on Field Day, with headphones, as I usually do,
>when some onlookers wanted to hear what was going on. I flipped
>SPKRS+PHONES=YES, then along came a strong signal, and poof! no
>speaker audio.
>
>AGC SLP was zero, and AGC THR was 020. Front panel AGC was FAST.
>
>This failure is really getting old, especially at $120 a pop to
>get it fixed.
>
>Dave Hachadorian, K6LL
>Big Bear Lake, CA
>
>

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Phil Wheeler-2

Re: K3 speaker amp chip bites the dust again

In reply to this post by Dave Hachadorian-2

Some years ago I learned to take only expendable
items to Field Day: Myself :-)

Otherwise I give items to the Club: Those things
always seem to survive!

Phil W7OX

On 7/1/14, 12:28 PM, Dave Hachadorian wrote:

> I guess I've blown the speaker amp IC in my K3
> again. This is the third time this has happened,
> twice in one radio and once in another.
>
> In this case, the radio had both the AF Output
> Mod Kit (pair of 470 ohm resistors) and the
> E85056 Audio Protection Assembly Circuit Board
> installed.
>
> I was operating on Field Day, with headphones,
> as I usually do, when some onlookers wanted to
> hear what was going on. I flipped
> SPKRS+PHONES=YES, then along came a strong
> signal, and poof! no speaker audio.
>
> AGC SLP was zero, and AGC THR was 020. Front
> panel AGC was FAST.
>
> This failure is really getting old, especially
> at $120 a pop to get it fixed.
>
> Dave Hachadorian, K6LL
> Big Bear Lake, CA
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> .
> ______________________________________________________________
>
> 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]
>

Joe Subich, W4TV-4

Re: K3 speaker amp chip bites the dust again

In reply to this post by Dave Hachadorian-2

With SLP=0 and THR=20 you have essentially *no* AGC action. That
means nothing is protecting the audio amplifier from strong inputs.

I leave it to Wayne or Lyle to calculate the overall gain from noise
floor to maximum DSP output but if one has set the audio for comfort
on a S4-S6 signal the audio amp is running along at roughly 1.5W
into the speaker. When that S9+10 dB signal comes along and you have
no AGC even if the audio amplifier is expected to produce only 20 dB
more power, the 3.1W amplifier is going to die when asked to produce
more than 150 W of peak power.

73,

... Joe, W4TV

On 2014-07-01 3:28 PM, Dave Hachadorian wrote:

> I guess I've blown the speaker amp IC in my K3 again. This is the third
> time this has happened, twice in one radio and once in another.
>
> In this case, the radio had both the AF Output Mod Kit (pair of 470 ohm
> resistors) and the E85056 Audio Protection Assembly Circuit Board
> installed.
>
> I was operating on Field Day, with headphones, as I usually do, when
> some onlookers wanted to hear what was going on. I flipped
> SPKRS+PHONES=YES, then along came a strong signal, and poof! no speaker
> audio.
>
> AGC SLP was zero, and AGC THR was 020. Front panel AGC was FAST.
>
> This failure is really getting old, especially at $120 a pop to get it
> fixed.
>
> Dave Hachadorian, K6LL
> Big Bear Lake, CA
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> .
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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>

Ross Primrose

Re: K3 speaker amp chip bites the dust again

On 7/1/2014 4:10 PM, Joe Subich, W4TV wrote:
>
> more power, the 3.1W amplifier is going to die when asked to produce
> more than 150 W of peak power.

In a properly engineered design, the amp may clip like crazy, but it
should be able to survive such abuse indefinitely....

73, Ross N4RP

>
> 73,
>
> ... Joe, W4TV
>
>
> On 2014-07-01 3:28 PM, Dave Hachadorian wrote:
>> I guess I've blown the speaker amp IC in my K3 again. This is the third
>> time this has happened, twice in one radio and once in another.
>>
>> In this case, the radio had both the AF Output Mod Kit (pair of 470 ohm
>> resistors) and the E85056 Audio Protection Assembly Circuit Board
>> installed.
>>
>> I was operating on Field Day, with headphones, as I usually do, when
>> some onlookers wanted to hear what was going on. I flipped
>> SPKRS+PHONES=YES, then along came a strong signal, and poof! no speaker
>> audio.
>>
>> AGC SLP was zero, and AGC THR was 020. Front panel AGC was FAST.
>>
>> This failure is really getting old, especially at $120 a pop to get it
>> fixed.
>>
>> Dave Hachadorian, K6LL
>> Big Bear Lake, CA
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> .
>> ______________________________________________________________
>> 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
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>
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--
FCC Section 97.313(a) “At all times, an amateur station must use the minimum transmitter power necessary to carry out the desired communications.”

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Dave Hachadorian-2

K3 speaker amp chip bites the dust again - CORRECTION!

In reply to this post by Joe Subich, W4TV-4

My posting this morning about blowing the speaker amp chip was in
error. Further investigation reveals that I actually blew out
the K3's internal speaker. Ohmmeter measurement at the speaker
terminals shows that the coil is wide open. This is really good
news, because the speaker is easily replaceable in the field.

It's also good news because it points out the efficacy of the
E85056 protection mod.

My apologies for making a wrong assumption. The symptoms were
exactly the same as the two previous failures of the speaker amp.

Dave Hachadorian, K6LL
Yuma, AZ

.

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Mike K2MK

Re: K3 speaker amp chip bites the dust again - CORRECTION!

Hi Dave,

I'm glad you found a solution and it's good to know that the mods work. You might want to take this opportunity to reevaluate your AGC settings. I use headphones and anything above 010 is painful. I used to set it to 012 to help my brain work weak signals but the occasional strong signal felt like Q-tips piecing my ear drums. Ramping the AGC THR up to 020 is unthinkable for me.

73,
Mike K2MK

Dave Hachadorian-2 wrote

My posting this morning about blowing the speaker amp chip was in
error. Further investigation reveals that I actually blew out
the K3's internal speaker. Ohmmeter measurement at the speaker
terminals shows that the coil is wide open. This is really good
news, because the speaker is easily replaceable in the field.

It's also good news because it points out the efficacy of the
E85056 protection mod.

My apologies for making a wrong assumption. The symptoms were
exactly the same as the two previous failures of the speaker amp.

Dave Hachadorian, K6LL

Elecraft mailing list

Re: K3 speaker amp chip bites the dust again - CORRECTION!

In reply to this post by Dave Hachadorian-2

Wow Dave you spooked me. I just completed the protection install before leaving Yuma for Astoria. I am glad to hear the install was not in vain. hi hi

Bill J K7BRR Yuma

Message: 13
Date: Tue, 1 Jul 2014 17:53:59 -0700
From: "Dave Hachadorian" <[hidden email]>
To: "Reflector Elecraft" <[hidden email]>
Subject: [Elecraft] K3 speaker amp chip bites the dust again -
CORRECTION!
Message-ID: <058BEFA1FA9E42939B8ED88C253D8CDA@Toshiba>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response

My posting this morning about blowing the speaker amp chip was in
error. Further investigation reveals that I actually blew out
the K3's internal speaker. Ohmmeter measurement at the speaker
terminals shows that the coil is wide open. This is really good
news, because the speaker is easily replaceable in the field.

It's also good news because it points out the efficacy of the
E85056 protection mod.

My apologies for making a wrong assumption. The symptoms were
exactly the same as the two previous failures of the speaker amp.

Dave Hachadorian, K6LL
Yuma, AZ
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Nr4c

Re: K3 speaker amp chip bites the dust again - CORRECTION!

I'm not sure where it is accessed but there is an audio limiter to prevent this from happening. Helps when AGC is OFF.

Sent from my iPhone
...nr4c. bill

> On Jul 2, 2014, at 2:55 PM, "William C. Johnson via Elecraft" <[hidden email]> wrote:
>
> Wow Dave you spooked me. I just completed the protection install before leaving Yuma for Astoria. I am glad to hear the install was not in vain. hi hi
>
> Bill J K7BRR Yuma
>
> Message: 13
> Date: Tue, 1 Jul 2014 17:53:59 -0700
> From: "Dave Hachadorian" <[hidden email]>
> To: "Reflector Elecraft" <[hidden email]>
> Subject: [Elecraft] K3 speaker amp chip bites the dust again -
> CORRECTION!
> Message-ID: <058BEFA1FA9E42939B8ED88C253D8CDA@Toshiba>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> My posting this morning about blowing the speaker amp chip was in
> error. Further investigation reveals that I actually blew out
> the K3's internal speaker. Ohmmeter measurement at the speaker
> terminals shows that the coil is wide open. This is really good
> news, because the speaker is easily replaceable in the field.
>
> It's also good news because it points out the efficacy of the
> E85056 protection mod.
>
> My apologies for making a wrong assumption. The symptoms were
> exactly the same as the two previous failures of the speaker amp.
>
> Dave Hachadorian, K6LL
> Yuma, AZ
> ______________________________________________________________
> 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]