Posted by
Dave Van Wallaghen on
Jan 24, 2009; 2:13pm
URL: http://elecraft.85.s1.nabble.com/KRX3-Installation-R91-mod-tp2208918.html
Hi all,
At first, I was only going to contact Ron with this as I was too
embarrassed to reveal that I had maimed the RF board on my K3. But, I
then thought maybe someone else could benefit from my experience and
public humility ;-)
I have an early serial number #338 and needed to make the modification
to R91 on the RF board as described on page 21 of the KRX3 Installation
Manual. In doing so, I was having a hard time getting the 27 ohm
resistor lead to tack onto the (looking at Figure 20) right pad of R91.
I made multiple attempts and couldn't get a clean connection until I
eventually lifted the pad. I was using a small but short soldering tip
at 720 degrees. In my zeal to get a nicer connection, I simply played
around with it too long and with too much heat, lifted the pad. Using a
longer, narrower tip (as I am now) would probably have worked better.
After the horror and high emotion subsided, I sat down to figure out
what could be done and hence a question as to my solution. Looking at
the schematic for the RF board, it looks like the only connection to the
right pad of R91 is pin 14 of U7. Does that seem correct to anyone else?
I removed R91 and was able to solder a 22 ohm 1/8 watt resistor to the
remaining trace of pin 14 of U7 and the pad next to R91 as outlined in
the directions. DMM measurements between U7 pin 14 and the left pad of
R91 show 22 ohms, so I'm pretty sure I was able to salvage the situation.
I will continue with the installation this morning, but would like some
concurrence that what I've done looks correct to someone else's eyes
before I power this beast back up.
BTW - Since I was going to install the KRX3, I decided to make the mods
for the K3 Synthesizer ALS, Rear RS232 and Audio RF mods, K3 Amp Output
Mod and the Front Panel Mic Mod. Having to somewhat disassemble the unit
for the KRX3 anyway made doing these mods very simple. And as usual,
Ron's documentation for these mods was nothing short of excellent,
including some nice tips for lining things back up to guarantee all
connectors and boards line up the way they are supposed to. As usual, my
impatience leads me to push ahead of the text to get the job done, but
if you follow everything Ron has written you will be guaranteed success.
Also, in my original K3 installation manual, the first KSYN3 board was
not mounted with split lock washers on the non-component side of the
board. Since I made the mod to it, I did remount it with the split lock
washers as described in the KRX3 manual. I assume there is no problem
with that?
Now, back to work...
Dave W8FGU
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