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Mike, NI2S's Ham Blog

Page 14

24-JAN-08: Continued.  RF MotherBoard Assembly

Now, on to finish the RF motherboard (still a ton of work to be done on this board)....

The resumption of work on the RF board starts with some 40+ 1/4 watt resistor installs.  For me, this is the most perilous activity of assembly due to my color blindness.  I am trying to be cautious, and measure each resistor before I install it to be sure it's the correct value.  If I have erred on the VOM setting, then I could install the wrong resistor.  Reds, browns, and greens all blend together for me, and of course many of these resistors have reds, browns and greens.   After a 'major' section of work has been complete, I will post some pics of the work and a discussion of the challenges if any.  Here are 3 pics of the resistors, resistor packs, as well as a few diodes that I installed:

   

After the resistor install, the next grouping was for diodes, and here I encountered another temporary road block peculiar to my K2 build.  As I mentioned at the outset, this K2 is an old kit.  I bought it in 2000(!) and for one reason or another didn't start the build until 2006(!).   The kit I bought was 'rev A'.  I purchased a series upgrade kits to bring the rig to a 'rev b'.  The rev b upgrade included a new manual in rev b vintage along with parts, chips, and new PCB's.  Here lies the snag.  Some of the diode part numbers to be installed starting on Pg 50 have changed since I bought the kit.  Since none of the diodes in question came with the rev b kit, I should be able to use the Rev A parts that were designated for these diode positions on the PCB - right?. Right.  However, in the spirit of NEVER assume, I have emailed Elecraft tech support this evening to confirm this.  I did try to find a reference guide on the web that might have indicated x part from this manufacturer equals y part from that manufacturer, but no luck.  So, I wait for tech support's response.  Based on prior experience, I should have a reply tomorrow. 

24-JAN-08:  True to form Elecraft responded this morning to my inquiry and provided a surprising answer - this exchange is proof positive that the only dumb question is the one that isn't asked.  Here is what Tech Support had to say:

"The MVAM108 diodes are OK to use. They were just discontinued, so we had to get an alternate.
D9 was changed to a 1N5711 for better wattmeter accuracy. Resistor R68 also has to be changed to 226 ohms, 1%."

 
Waiting for parts to come to NJ from California is a bit of a pain (The missing capacitor and replacement toroid have not arrived via snail mail yet).  I am going to see if I can get these components (except the toroid) from Lashen Electronics of Denville, or Wayne Electronics of Wayne.  Anyone reading this blog that knows of another electronic component supplier in the Northern New Jersey area, please email me.