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K2 SSB audio distorted. Realignment, MIC gain mod etc.

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Andreas Hofmann-3

K2 SSB audio distorted. Realignment, MIC gain mod etc.

Hi

I have SN 2555 and have exclusively used it for CW. Now, I am trying to use it for SSB, but I am getting reports of distortion. Even with SSBA 1 and SSBC 1:1. If I speak really quietly, with microphone about 10 inches away, the distortion is manageable but not fully gone. ALC seems to go a couple of LEDS before it settles down to 1 LED on 40m. This happens for both MH2 and the Heil Pro-Set Plus!. I believe, I did some mods years ago to increase MIC gain, but I have a hard time to find the information now on the website to double check.

What would be the mostly likely reason my audio is distorted?
I scanned the manuals but there is no procedure to align the MIC gain anywhere. How can this be done?
The rig is 7-8 years old, I am considering spending an evening and realigning everything. Is this something that could fix this issue?
If my memory is right, and there was a MIC gain mod at some point, can someone send me a copy/details, so I can investigate if I have it and possibly undo it?

Thanks
And 73, Andy, KU7T
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Don Wilhelm-4

Re: K2 SSB audio distorted. Realignment, MIC gain mod etc.

Andy,

I assume you have the K2/100 rather than the K2/10. The KPA100 can
couple into the KSB2 board giving audio distortion. Remove the right
side panel and tuck the ribbon cable and speaker cable up into the space
between the KPA100 and the top of the Control Board.

Mods to increase the mic gain have been several - change the value of
resistor R14 is the simplest, adding a mic preamp is a bit more
involved, and for those who want a bit better performance there is the
KI6WX SSB Increased RF Gain mod. If the latter is installed in a
K2/100, changes to the KSB2 ALC circuit should also be made - if you
have a transistor added to your KSB2 near U5 (either on the top or
bottom of the board), then you have that mod installed - I can give you
the ALC changes that should be made.

Since you have an older KPA100, do you have the shield up to date? You
should have a shield on the speaker magnet, there should be clips on the
shield and there should be a direct connection between the top of the
shield and the SO-239 jack (that connection is usually made with 2
solder lugs connected together).

73,
Don W3FPR

On 12/31/2011 2:47 AM, Andreas Hofmann wrote:

> Hi
>
> I have SN 2555 and have exclusively used it for CW. Now, I am trying to use it for SSB, but I am getting reports of distortion. Even with SSBA 1 and SSBC 1:1. If I speak really quietly, with microphone about 10 inches away, the distortion is manageable but not fully gone. ALC seems to go a couple of LEDS before it settles down to 1 LED on 40m. This happens for both MH2 and the Heil Pro-Set Plus!. I believe, I did some mods years ago to increase MIC gain, but I have a hard time to find the information now on the website to double check.
>
> What would be the mostly likely reason my audio is distorted?
> I scanned the manuals but there is no procedure to align the MIC gain anywhere. How can this be done?
> The rig is 7-8 years old, I am considering spending an evening and realigning everything. Is this something that could fix this issue?
> If my memory is right, and there was a MIC gain mod at some point, can someone send me a copy/details, so I can investigate if I have it and possibly undo it?
>
> Thanks
> And 73, Andy, KU7T
>

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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Andreas Hofmann-3

Re: K2 SSB audio distorted. Realignment, MIC gain mod etc.

Thank you very much for the information Don. I opened the rig and took a look at it. Also, found some references to mods that I did. Here is the info:

- Yes, I have the K2/100.
- The following mods related to KPA100 have been made:
o K2 12/10m BPF mod (from June 2002)
o K2 VFO ALC mod (from June 2002)
o KPA 100 shield upgrade (from June 2003)
o KPA 100 Upgrade kit (Rev. B, Feb 2004)
- The cables are not tucked in between the KPA100 and the top of the Control board, I will try this next and let you know.
- I also see a mod where the audio line level is brought out to the rear of the K2 for sound card connection (from J5). I will take the cable out for now and see if this makes a difference.
- R14 on the KSB2 board is 5.6K and R2 is 1K. I believe that means the simple mic gain mod has been made that was to swap R2 and R14. However, I found this http://elecraft.365791.n2.nabble.com/Mic-Gain-K2-100-td394881.html#a394889 .I think I did that because my VOX did not work right, even now, I am not happy by the VOX operations. However, since I am using MicroHam Keyer II and foot switch, I am not sure I need to worry about VOX. Possibly, I should undo this change? What do you think?
- You mention the speaker shield. Even though I have the shield update kit installed, I do NOT have any type of shield on the speaker magnet. Ideas?

Thank you very much for your help. Looking forward to some pointers.

Thanks and 73,
Andreas, KU7T

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Saturday, December 31, 2011 4:17 AM
To: Andreas Hofmann
Cc: [hidden email]
Subject: Re: [Elecraft] K2 SSB audio distorted. Realignment, MIC gain mod etc.

Andy,

I assume you have the K2/100 rather than the K2/10. The KPA100 can couple into the KSB2 board giving audio distortion. Remove the right side panel and tuck the ribbon cable and speaker cable up into the space between the KPA100 and the top of the Control Board.

Mods to increase the mic gain have been several - change the value of resistor R14 is the simplest, adding a mic preamp is a bit more involved, and for those who want a bit better performance there is the KI6WX SSB Increased RF Gain mod. If the latter is installed in a K2/100, changes to the KSB2 ALC circuit should also be made - if you have a transistor added to your KSB2 near U5 (either on the top or bottom of the board), then you have that mod installed - I can give you the ALC changes that should be made.

Since you have an older KPA100, do you have the shield up to date? You should have a shield on the speaker magnet, there should be clips on the shield and there should be a direct connection between the top of the shield and the SO-239 jack (that connection is usually made with 2 solder lugs connected together).

73,
Don W3FPR

On 12/31/2011 2:47 AM, Andreas Hofmann wrote:

Don Wilhelm-4

Re: K2 SSB audio distorted. Realignment, MIC gain mod etc.

Andreas,

Yes, do tuck those cables up and away from the KSB2 board.

The value of R14 may be OK, but I worry about the 1k at R2, that should
be 5.6k so not to overdrive the balanced modulator. In addition to
that, you might also put a 2.2k resistor between U5 pins 1 and 2 (it is
easiest to mount on the carrier balance trimmer, it goes across the two
outer leads - not the center lead).

The VOX on the K2 is the one thing that is not the best. If you can use
PTT rather than VOX, you will obtain better performance.

73,
Don W3FPR

On 1/4/2012 2:51 PM, Andreas Hofmann wrote:

> Thank you very much for the information Don. I opened the rig and took a look at it. Also, found some references to mods that I did. Here is the info:
>
> - Yes, I have the K2/100.
> - The following mods related to KPA100 have been made:
> o K2 12/10m BPF mod (from June 2002)
> o K2 VFO ALC mod (from June 2002)
> o KPA 100 shield upgrade (from June 2003)
> o KPA 100 Upgrade kit (Rev. B, Feb 2004)
> - The cables are not tucked in between the KPA100 and the top of the Control board, I will try this next and let you know.
> - I also see a mod where the audio line level is brought out to the rear of the K2 for sound card connection (from J5). I will take the cable out for now and see if this makes a difference.
> - R14 on the KSB2 board is 5.6K and R2 is 1K. I believe that means the simple mic gain mod has been made that was to swap R2 and R14. However, I found this http://elecraft.365791.n2.nabble.com/Mic-Gain-K2-100-td394881.html#a394889 .I think I did that because my VOX did not work right, even now, I am not happy by the VOX operations. However, since I am using MicroHam Keyer II and foot switch, I am not sure I need to worry about VOX. Possibly, I should undo this change? What do you think?
> - You mention the speaker shield. Even though I have the shield update kit installed, I do NOT have any type of shield on the speaker magnet. Ideas?
>
> Thank you very much for your help. Looking forward to some pointers.
>
> Thanks and 73,
> Andreas, KU7T
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Saturday, December 31, 2011 4:17 AM
> To: Andreas Hofmann
> Cc: [hidden email]
> Subject: Re: [Elecraft] K2 SSB audio distorted. Realignment, MIC gain mod etc.
>
> Andy,
>
> I assume you have the K2/100 rather than the K2/10. The KPA100 can couple into the KSB2 board giving audio distortion. Remove the right side panel and tuck the ribbon cable and speaker cable up into the space between the KPA100 and the top of the Control Board.
>
> Mods to increase the mic gain have been several - change the value of resistor R14 is the simplest, adding a mic preamp is a bit more involved, and for those who want a bit better performance there is the KI6WX SSB Increased RF Gain mod. If the latter is installed in a K2/100, changes to the KSB2 ALC circuit should also be made - if you have a transistor added to your KSB2 near U5 (either on the top or bottom of the board), then you have that mod installed - I can give you the ALC changes that should be made.
>
> Since you have an older KPA100, do you have the shield up to date? You should have a shield on the speaker magnet, there should be clips on the shield and there should be a direct connection between the top of the shield and the SO-239 jack (that connection is usually made with 2 solder lugs connected together).
>
> 73,
> Don W3FPR
>
>
> On 12/31/2011 2:47 AM, Andreas Hofmann wrote:
>> Hi
>>
>> I have SN 2555 and have exclusively used it for CW. Now, I am trying to use it for SSB, but I am getting reports of distortion. Even with SSBA 1 and SSBC 1:1. If I speak really quietly, with microphone about 10 inches away, the distortion is manageable but not fully gone. ALC seems to go a couple of LEDS before it settles down to 1 LED on 40m. This happens for both MH2 and the Heil Pro-Set Plus!. I believe, I did some mods years ago to increase MIC gain, but I have a hard time to find the information now on the website to double check.
>>
>> What would be the mostly likely reason my audio is distorted?
>> I scanned the manuals but there is no procedure to align the MIC gain anywhere. How can this be done?
>> The rig is 7-8 years old, I am considering spending an evening and realigning everything. Is this something that could fix this issue?
>> If my memory is right, and there was a MIC gain mod at some point, can someone send me a copy/details, so I can investigate if I have it and possibly undo it?
>>
>> Thanks
>> And 73, Andy, KU7T
>>
>
> ______________________________________________________________
> 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
>

Andreas Hofmann-3

Re: K2 SSB audio distorted. Realignment, MIC gain mod etc.

Don,

Your suggestions worked. I tucked the wires better away from the KSB2 and replaced R2 back to its original value (VOX is now unusable, but I am fine with it). The distortions are gone with SSBC 1-1 and signal gets a little distorted with more compression but that is normal I think.

I noticed that there is quite a different of RF levels between different bands with the same mike. I am considering doing the other SSB mods as you suggested from http://www.qrpproject.de/Media/pdf/SSBModsUK.pdf. It seems that these mods will help with the level difference on different bands.

Thank you so much for your help.
Andreas, KU7T

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Wednesday, January 04, 2012 2:38 PM
To: Andreas Hofmann
Cc: [hidden email]
Subject: Re: [Elecraft] K2 SSB audio distorted. Realignment, MIC gain mod etc.

Andreas,

Yes, do tuck those cables up and away from the KSB2 board.

The value of R14 may be OK, but I worry about the 1k at R2, that should be 5.6k so not to overdrive the balanced modulator. In addition to that, you might also put a 2.2k resistor between U5 pins 1 and 2 (it is easiest to mount on the carrier balance trimmer, it goes across the two outer leads - not the center lead).

The VOX on the K2 is the one thing that is not the best. If you can use PTT rather than VOX, you will obtain better performance.

73,
Don W3FPR

On 1/4/2012 2:51 PM, Andreas Hofmann wrote:

> Thank you very much for the information Don. I opened the rig and took a look at it. Also, found some references to mods that I did. Here is the info:
>
> - Yes, I have the K2/100.
> - The following mods related to KPA100 have been made:
> o K2 12/10m BPF mod (from June 2002)
> o K2 VFO ALC mod (from June 2002)
> o KPA 100 shield upgrade (from June 2003)
> o KPA 100 Upgrade kit (Rev. B, Feb 2004)
> - The cables are not tucked in between the KPA100 and the top of the Control board, I will try this next and let you know.
> - I also see a mod where the audio line level is brought out to the rear of the K2 for sound card connection (from J5). I will take the cable out for now and see if this makes a difference.
> - R14 on the KSB2 board is 5.6K and R2 is 1K. I believe that means the simple mic gain mod has been made that was to swap R2 and R14. However, I found this http://elecraft.365791.n2.nabble.com/Mic-Gain-K2-100-td394881.html#a394889 .I think I did that because my VOX did not work right, even now, I am not happy by the VOX operations. However, since I am using MicroHam Keyer II and foot switch, I am not sure I need to worry about VOX. Possibly, I should undo this change? What do you think?
> - You mention the speaker shield. Even though I have the shield update kit installed, I do NOT have any type of shield on the speaker magnet. Ideas?
>
> Thank you very much for your help. Looking forward to some pointers.
>
> Thanks and 73,
> Andreas, KU7T
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Saturday, December 31, 2011 4:17 AM
> To: Andreas Hofmann
> Cc: [hidden email]
> Subject: Re: [Elecraft] K2 SSB audio distorted. Realignment, MIC gain mod etc.
>
> Andy,
>
> I assume you have the K2/100 rather than the K2/10. The KPA100 can couple into the KSB2 board giving audio distortion. Remove the right side panel and tuck the ribbon cable and speaker cable up into the space between the KPA100 and the top of the Control Board.
>
> Mods to increase the mic gain have been several - change the value of resistor R14 is the simplest, adding a mic preamp is a bit more involved, and for those who want a bit better performance there is the KI6WX SSB Increased RF Gain mod. If the latter is installed in a K2/100, changes to the KSB2 ALC circuit should also be made - if you have a transistor added to your KSB2 near U5 (either on the top or bottom of the board), then you have that mod installed - I can give you the ALC changes that should be made.
>
> Since you have an older KPA100, do you have the shield up to date? You should have a shield on the speaker magnet, there should be clips on the shield and there should be a direct connection between the top of the shield and the SO-239 jack (that connection is usually made with 2 solder lugs connected together).
>
> 73,
> Don W3FPR
>
>
> On 12/31/2011 2:47 AM, Andreas Hofmann wrote:
>> Hi
>>
>> I have SN 2555 and have exclusively used it for CW. Now, I am trying to use it for SSB, but I am getting reports of distortion. Even with SSBA 1 and SSBC 1:1. If I speak really quietly, with microphone about 10 inches away, the distortion is manageable but not fully gone. ALC seems to go a couple of LEDS before it settles down to 1 LED on 40m. This happens for both MH2 and the Heil Pro-Set Plus!. I believe, I did some mods years ago to increase MIC gain, but I have a hard time to find the information now on the website to double check.
>>
>> What would be the mostly likely reason my audio is distorted?
>> I scanned the manuals but there is no procedure to align the MIC gain anywhere. How can this be done?
>> The rig is 7-8 years old, I am considering spending an evening and realigning everything. Is this something that could fix this issue?
>> If my memory is right, and there was a MIC gain mod at some point, can someone send me a copy/details, so I can investigate if I have it and possibly undo it?
>>
>> Thanks
>> And 73, Andy, KU7T
>>
>
> ______________________________________________________________
> 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
>