[Elecraft] K3 AF Upgrade Kit (for speaker amplifier and LINE OUTs)

[Eric Swartz - WA6HHQ, Elecraft]

This information and a mod manual are now on our K3 Enhancements and
Applications note page. See:

http://www.elecraft.com/K3/k3_app_notes.htm

I apologize for the delay getting this posted! It should have been up
earlier.

 >From that page:

Line-Out KIO3 R19/R20 Change:
About Oct 7, 2008
About S/N 1900

Speaker Amp RFC47 Change:
About Sept 25, 2008
About S/N 1830

(Dates and serial numbers are approximate and may vary slightly.)

73, Eric   WA6HHQ
------

N6WG wrote:
 > I would also like to know that please.
 > 73, Igor UA9CDC
 >
 >> Wayne
 >> Can you tell us the serial number at which
 >> these changes were incorporated?
 >> We need to know who needs to order them
 >> and who does not.
 >> Thanks and 73
 >> Bob N6WG
 >>
 >> ----- Original Message ----- From: "wayne burdick" <n6kr at elecraft.com>
 >> To: "Elecraft Reflector" <elecraft at mailman.qth.net>
 >> Sent: Thursday, November 13, 2008 10:40 AM
 >> Subject: [Elecraft] K3 AF Upgrade Kit (for speaker amplifier and LINE
 >> OUTs)
 >>
 >>
 >>> With minor circuit changes, both the K3's speaker amplifier and line
 >>> outputs can provide lower IMD (intermodulation distortion) at higher
 >>> signal levels. We've been testing these changes for a couple of
 >>> months, and have already phased them into production.
 >>>
 >>> These changes can easily be made to existing K3s. A kit of parts is
 >>> available (K3AFMDKT). All parts are leaded (not surface mount), and
 >>> full instructions are provided. See:
 >>>
 >>>    http://www.elecraft.com/order_form_parts.htm#K3%20Parts
 >>>
 >>> Details
 >>> -------
 >>>
 >>> SPEAKER AMP:  The mod kit includes a very low-resistance RF choke
 >>> for use at RFC47 on the RF board. This improves speaker amplifier
 >>> IMD by as much as 25 dB at moderate to high AF GAIN settings by
 >>> reducing the voltage drop across RFC47 during signal peaks.
 >>>
 >>> LINE OUT:  The kit also includes smaller resistor values for R19 and
 >>> R20 on the KIO3 module. At present R19 and R20 are about 600 ohms,
 >>> while the replacements drop the resistance to around 50 ohms. The
 >>> smaller resistors increase the available voltage swing at the output
 >>> of the LINE OUT transformers, which improves IMD at higher signal
 >>> levels.
 >>>
 >>> These two changes are independent. For example, if you never use
 >>> LINE OUTs, you might want to do only the speaker amp modification.
 >>>
 >>> 73,
 >>> Wayne
 >>> N6KR


wayne burdick wrote:
> With minor circuit changes, both the K3's speaker amplifier and line 
> outputs can provide lower IMD (intermodulation distortion) at higher 
> signal levels. We've been testing these changes for a couple of 
> months, and have already phased them into production.
>
> These changes can easily be made to existing K3s. A kit of parts is 
> available (K3AFMDKT). All parts are leaded (not surface mount), and 
> full instructions are provided. See:
>
>    http://www.elecraft.com/order_form_parts.htm#K3%20Parts
>
> Details
> -------
>
> SPEAKER AMP:  The mod kit includes a very low-resistance RF choke for 
> use at RFC47 on the RF board. This improves speaker amplifier IMD by 
> as much as 25 dB at moderate to high AF GAIN settings by reducing the 
> voltage drop across RFC47 during signal peaks.
>
> LINE OUT:  The kit also includes smaller resistor values for R19 and 
> R20 on the KIO3 module. At present R19 and R20 are about 600 ohms, 
> while the replacements drop the resistance to around 50 ohms. The 
> smaller resistors increase the available voltage swing at the output 
> of the LINE OUT transformers, which improves IMD at higher signal levels.
>
> These two changes are independent. For example, if you never use LINE 
> OUTs, you might want to do only the speaker amp modification.
>
> 73,
> Wayne
> N6KR
>
> ---
>
> http://www.elecraft.com
>
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