If you look at K1 builder alert #1, R39 is discussed there. C76 is installed right next to it. Look also at the schematic for the K1 page 79 "Appendix B RF Board" in the lower left hand corner where C75 and R39 are shown.
Here is the builder alert #1... "K1 builder alert: Minor T-R switch mod Fri, 1 Dec 2000 Impact: All K1's through S/N 400 Background: During testing of the KAT1 antenna tuner, we intentionally created worst-case conditions, such as dead shorts, opens, and large transients. As a result of these experiments, we've decided to add a resistor to the K1's T-R switch circuitry. (Technical details can be found below.) This has no effect on receive or transmit performance, but helps protect the transmitter from extreme mismatch conditions. Applicability: We recommend that this minor modification be made to all K1s, even though it's very unlikely that you'd ever encounter a problem during normal use. If you have not yet received your K1, keep a copy of this builder alert, then check the manual revision when the kit arrives. If your manual is rev. D, your kit includes the resistor and the modification instructions. If the manual is rev. C, make the modification as described below. In this case you'll need to supply your own resistor, which can be in the range of 1.8 to 2.2 K (5% or 10%, 1/8-watt, 1/4-watt or higher rating). Modification instructions: 1. Remove the Filter board and locate RP4, in the back-left corner near the key jack. 2. On the bottom of the RF board, solder one end of a 1.8K, 2.0K, or 2.2K resistor to pin 1 of RP4 (the round pad). 3. Solder the other lead of this resistor to the nearby ground pad for crystal X6. This pad can be easily identified on the top side of the board; it has the "X6" label directly above it. Technical Details: Under extreme load or transient conditions, high RF voltages or currents can appear on the power supply and ground leads, as well as the T-R switch control lines (6R and 6T). Q14 (part of the TX Buffer circuit) is connected to 6R, and is supposed to remain off during transmit. Adding a 1.8K (approx.) resistor from the base of Q14 to ground significantly improves the noise immunity of this circuit, without compromising the normal function of Q14 when 6R is turned on." That builder alert and these instructions from the KAT1 manual should be all you need... "The following five steps are only necessary if you have revision D or earlier of the K1 RF board. On later revisions, these parts will already have been installed during RF board assembly. Install resistor RF-R39 (1.8 k, brown-gray-red) on the bottom of the RF board between Q14 base and ground, if you haven’t already. This is described in detail on page 31 of the K1 owner’s manual (right column, last assembly step). Solder capacitor RF-C76 (.01 μF, “103”) across RF-R39, the resistor in the previous step. Use short leads, and fold the capacitor down so it won’t hit the bottom cover." Chuck, KE9UW Lionel Trains, TCA, LCCA, LRRC aka Jack, BMW Motorcycles BMWMOA #224 ________________________________________ From: elecraft-boun...@mailman.qth.net [elecraft-boun...@mailman.qth.net] on behalf of Philipp Kaysser, DK3IP [dk...@speck-kaysser.de] Sent: Saturday, February 09, 2013 6:22 AM To: elecraft@mailman.qth.net Subject: [Elecraft] KAT1 installation Hello, I am currently trying to build up and install a KAT1 into my K1 # 154. I have just updated the firmware to version 1.09 and made all changes of the K1 upgrade kit. Now I am working my way through the KAT1 assembly and operating instructions revision C, Jan. 18, 2001. I am stuck at page 7 preparing the RF board. I have a revision D K1 RF board. The KAT1 manual instructions tell me to install resistor RF-R39 and capacitor RF-C76 as described in detail on page 31 of the K1 owner's manual. In my K1 owner's manual (revision C, Oct. 9, 2000) there are no instructions to do this on page 31. As the currently downloadable K1 manual on the Elecraft homepage is for the latest generation RF board (revision I, April 15, 2011) the instructions given there are also not helpful for me. I presume the instructions I need are somewhere in a K1 manual between revision C and I. Does anyone of you have such an old manual which contains the right instructions for me and send me a PDF of this manual by email (dk3ip at darc.de)? 73, Philipp, DK3IP ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
