Hi Dave,
Dave you indeed had an unfortunate experience! >After doing a lot of pre-modification research on my #371, I determined that the mod had been done, only partially, before it was shipped to me. The R33 and R40 were still in place and not removed or jumpered as the mod instructed. They both appeared to be 1K ohm SMD resistors. Rather than using visual inspection, I recommend everyone use a VOM to actually measure R33 and R40. Apparently the factory mod uses SMD resistors with very low resistance instead of an actual short. Most SMD resistors are marked with 3 numbers such as "333" The first two digits are the first two significant digits and the second is a power of 10 multiplier. Thus "333" signifies 33 x 10^3 = 33k ohms. I'm actually not sure what markings are on the factory SMD shorts but they should include that in the mod instructions. I've sometimes seen "000" used for SMD shorts but the safest thing is to measure them, and both R33 and R40 can be accurately measured "in-circuit", so trust your measurements. >Here's my issue. >In removing the SMD devices (which I undertook as suggested by first cutting them in half with miniature dikes to avoid the necessity of using too much heat to the pads on the pc board) I very briefly applied heat from a 20 watt iron and solderwick for a fraction of a second to remove the remnants of the devices. Not only did the remnants come off but so did one of the solder pads from the pc board. So much for my introduction to SMD de-soldering. Rather than removing R33 and R40, another alternative is to simply place a short across them. This can be done easily by soldering a small piece of component lead wire bent into a U across the existing resistors. >So should R33 and R40 be left in place or removed? I do not understand how it does or does not make a difference either way. IMO that should have been addressed in the HAGC mod instructions. It doesn't matter as long as they are shorted, either with a piece of wire across the existing resistors or by replacing them with SMD resistor "shorts". A short is a short. I always check my work by checking with a VOM/DMM across adjacent traces (i.e. in series with the SMD pads). >Morale of my story is proceed very carefully in undertaking soldering on these boards. They can be unforgiving. If you've never done this before, I suggest practicing with some scrap SMD boards first. Most of us have some old scrap SMD boards in our junk box and this is a good way to practice your technique before touching the K3. >BTW the 'CW rise time mod' was not performed on my unit. That was done with no problem. I used the through hole capacitor on this one. I wonder how you determined that since SMD capacitors are *NOT* marked? The only way I know is to use a capacitance meter which does give a correct reading "in-circuit". Unmodified units use 1 uF and modified units use 0.1uF, but they look identical visually. Again, trust your measurements and not visual inspection. Someone earlier mentioned the SMD LED orientation. The correct orientation is with the two tiny green dots toward the front of the K3 (thanks W4WFB). Sorry you had a bad experience and I hope this helps others! 73, Bill -- View this message in context: http://www.nabble.com/K3---HAGCMDKT-mod-kit-tp17524966p17525437.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
