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

[Paul Christensen]

As previously discussed, the replacement RFC in question is a 100 uH (not 10 
uH) Bourns (old J.W. Miller) part number 5800-101-RC.  Whether the old RFC 
is depicted on the schematic as 10 uH or 100 uH is immaterial as far as the 
mod is concerned.  What's called for in the replacement procedure is the 100 
uH choke.

http://www.bourns.com/pdfs/5800_series.pdf

Paul, W9AC

----- Original Message ----- 
From: "hb9wi" <willyschwarz at swissmail.com>
To: <elecraft at mailman.qth.net>
Sent: Thursday, November 20, 2008 1:51 PM
Subject: Re: [Elecraft] K3 AF Upgrade Kit (for speaker amplifier and LINE 
OUTs)



Speaker amplifier modification:
In the AF stage upgrade instruction page 1 it is mentioned:
“This mod changes RFC 47, 100 µH radio frequency choke that supplies power
to the K3 audio amplifier. The
original choke has a resistance of about 1.5 ohms. This resistance is high
enough to cause some clipping of the audio signal at moderate volume
settings, resulting in distortion products about 40 dB down. Replacing this
choke with a physically larger unit with a resistance of about 0.2 ohms
results in a 20 to 30 dB reduction in most distortion products”

On the K3 circuit diagram RFC47 is marked with a value of 10uH.
I plan to buy this choke locally “because the high shipping charges for the
kit to Switzerland”. Which value is now correct 10uH or 100uH?

73 Willy HB9WI

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