These are all excellent observations, IMX. I use a magnifying headset for a good many things. Excellent lighting is important too. My bench is equipped with two 100 watt 5800K compact fluorescent lamps (CFLs) on swing arms. The 5800K color temperature is close to sunlight where we humans have the highest visual acuity.
I've worked on a lot of tiny stuff even long before SMDs appeared - gyroscopic parts, etc., even a few old mechanical watches. I learned to never hold my hands in the air. I arrange my workbench so I have a rest for each hand and I only move my fingers to adjust tiny tools and small parts. It's easy to arrange impromptu hand rests if the work can't be laid flat on the bench. Small books alongside the work will do nicely so you can rest the side of your hand opposite your thumb on them while working. That's how I'm holding the iron and toothpick probe in Fig 15. An adjustable height chair is also important so I'm not hunched over to get down to the work or stretching to reach up to it. For stuff like this, I like to have the work at the same height as my upper chest when I'm sitting comfortably in my chair. The "piggyback" SMD resistor approach avoids the necessity of removing SMDs from the circuit board without damaging traces. Ron AC7AC From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Christensen Sent: Thursday, December 04, 2008 5:37 AM To: [email protected] Subject: Re: [Elecraft] K3 Audio Upgrade Mod > "I would argue for the piggyback approach. Use a pair of "sprung" tweezers that can grasp the SMT resistor at a comfortable angle." At first, I detested working with SMT parts. I slowly got over it and have developed a certain comfort level but I almost need to meditate first as the iron is warming up. For me, a magnifying headset is a must. Like most of you, my ability to work very closely on PCBs stopped nearly on the day of my 40th birthday and since then, my near vision has slowly gotten worse. I now wear bifocal contact lenses, but the magnifier is still needed for SMT work. Also, I need to limit my caffeinated coffee intake before working. There is no way I can work with the iron and parts while I'm caffinated. Way too much shaking. A well-lighted area anda good "mood" environment is also a must. I almost never conduct SMT work with family anywhere nearby. It's too easy to loose my focus and concentration -- and mistakes start escalating. Regarding the K3AF audio mod: I had no hesitation in removing the old SMT parts and directly replacing them with new values. Arguably, the "piggy-backing" attempt is more difficult since you're not working against a flat surface, like the PCB. Also, the area around the PCB's solder pads will be a bit more forgiving if alignment of the part is not perfect. Somewhere on the web, an ingenious fellow developed a slick "third hand" for SMT work The device is clamped to the edge of the PCB and pivots much the same way that we used to adjust a crystal radio's detector by varying the catwhisker arm position and tension on a piece of galena. The end of the catwhisker is then pressed upon the SMT part to retain tension while the left and right hands are applying heat and solder. Wish I new where to find one.... Paul, W9AC
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