** 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.pdfIt 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.htmWe 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
[hidden email] or via phone at
831-763-4211
73, Eric WA6HHQ
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