[Elecraft] K3 AF/RF Mod

[Paul Christensen]

BTW, the mod is likely possible with a future F/W change to allow changes 
just as the current menu allows for 'Normal" and 'Balance' audio functions. 
If that ever happens, the wiring mod is very easily reversible in less than 
a minute with no evidence left behind.

Paul, W9AC

----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <elecraft at mailman.qth.net>
Sent: Thursday, September 10, 2009 12:27 PM
Subject: [Elecraft] K3 AF/RF Mod


> Okay, I couldn't leave well enough alone...
>
> Yesterday morning, I was working a T30 station split on 40m with the K3's
> Sub Rx and became a bit unnerved with the manipulation of the K3's "Sub 
> AF"
> control when balancing between Main and Sub receivers.  Multiple quick
> reaches for the "balance" function on the upper Sub AF control's outer 
> ring
> was causing me to accidentally come in contact with the other controls.
> Looking at the K3 schematic, all four controls (Main AF, Sub AF, Main RF,
> and Sub RF) are all 10K in value.  Even when the K3's AF control furnction
> menu is selected for "Normal," rather than AF "Balance," a similar issue 
> can
> arrise when trying to quickly balance the Main/Sub AF controls on one 
> shaft.
>
> I removed the front panel to inspect the Front Panel PCB and thought a 
> swap
> of the Sub AF and Main RF controls could be easily accomplished.  Here's a
> "before" photo of the PCB area:
>
> http://216.229.20.37/images/K3-AF-1.jpg
>
> And the "after" wiring...
>
> http://216.229.20.37/images/K3-AF-2.jpg
>
> A hot glue gun can be used near the 5-pin header to keep the two ribbon
> cables from interfering with future front panel extractions and 
> insertions.
> Now, the upper controls handles Main AF (inner) + Main RF/SQL (outer). 
> The
> lower controls handle Sub AF/Balance (inner) and Sub RF (outer).
>
> When I engage split operations and use the Sub Rx, manipulating the 
> balance
> between Main AF and Sub RF is easier with a bit less propensity to
> accidentally come in contact with the adjacent controls since: (1) the
> Main/Sub AF balance function is now on the inner concentric control and
> extends out further from the front panel than the outer concentric ring; 
> and
> (2) the balance function is now moved to the bottom where the hand can
> approach the control from the bottom rather than directly in-line with the
> knob.
>
> If needed later for a sale, reversal of the mod is very easy.  Certainly,
> this mod is not for everyone.  However, I would think that in later PCB
> revisions, Elecraft could provide the option of selecting the existing
> format or the modified format at the time of purchase -- or to the builder
> who simply makes a few header pin changes during construction.
>
> Of course, the front panel legends also need changing and that's probably
> the biggest drawback to the mod.  In my case, I will use new legends 
> printed
> from a Brother 'P-Touch' printer -- printed with white lettering against
> black background tape.   Font size and type is adjustable to match the
> existing legends on the K3.
>
> Paul, W9AC
>
>
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