[Elecraft] K3/100 and Rev C Tech Alert - Important

[Eric Swartz - WA6HHQ, Elecraft]

** Spurious TX sidebands due to C3 installation on early Rev C KPA3 PC 
boards. **

We have determined that a small number of K3/100s and KPA3s left the 
factory earlier this year with capacitor C3 installed by mistake on 
early Revision C KPA3 PC boards.  This part location should be empty on 
Rev. C KPA3s.  Installation of C3 causes the PA bias supply to oscillate 
on some KPA3s at approximately 15-20 kHz, resulting in spurious TX 
sidebands at that spacing from the carrier.

S/N & Date Range:
A small number of K3/100s within approximately S/N 3000-3138. These 
radios were shipped approximately April 30 to June 2, 2009. 
Upgrade or repair KPA3s sent separately during this time period may also 
be affected.

After June 2, 2009, this problem was corrected for all K3/100s s/n 3139 
and later, and all Rev C KPA3s bought as an upgrade. This alert does not 
apply to Rev C KPA3s shipped after June 2, 2009.
 
Symptom: A strong TX spur, approximately -20 dB down from peak transmit 
power, spaced approximately 15-20 kHz on each side of the operating 
frequency.

Corrective Action: Remove capacitor C3 from the Rev C KPA3 PCB as 
described below.

A Tech. Alert App note (.pdf) can be downloaded from:
http://www.elecraft.com/K3/mods/K3%20Technical%20Alert%201.pdf

It contains detailed info and pictures.

Its also linked to from our K3 Mods and App notes Page:
http://www.elecraft.com/K3/k3_app_notes.htm

We apologize for this issue. We thought we had contacted all of the K3 
owners affected, but we have found a few we missed, so we are posting 
this here.

If after reading the Tech. Alert you have questions, please feel free to 
contact our Tech. group at k3support at elecraft.com or via phone at 
831-723-4211

73, Eric  WA6HHQ