Kit building 101 Part 1 The Basics

Art WØBA

Introduction:

Since those early days in the television repair shop wiring together two tube sockets and crossing the elements over connecting one socket pin to another to allow use of a replacement tube that was only electronically “similar” to a tube that had failed and was not on hand, free form electronics circuit building and later pre engineered kits has been in my blood.

Those free form, pre engineered, and/or kit circuit building efforts, were dismal failures sometimes, and other times performed beyond my wildest expectations. A given circuit could be built by one technician at the shop and work like a charm and built by another less successfully. With this kind of foundation and half a century of refusing to accept that the limitation might have been me, my skills at electronics kit building have been honed to a reasonably sharp edge. Lately I have observed that not everyone has had the time and masochism to develop electronics kit building skills so it makes sense to pass the smoldering soldering iron along to another generation of builders.

The focus for now will be surface mount devices and kits from suppliers like W1GHZ et al (WA3IAC), W6PQL, N2CEI (Down East Microwave, Inc.), and W7BAS.

Thanks to all my Elmers and family for giving me the will to go on when things went awry, congratulations when an effort was successful, and support all the way.

Table of contents:

Introduction

TOC

Environment and equipment

Selecting a kit

SMD soldering techniques

Actually build a kit

Packaging and human interface

On the air testing

 

 

Environment and equipment:

You may not be able to duplicate the environment I describe exactly, but that is not the intent of this section. Use the descriptions to achieve the best kit building environment you can. Pick a spot that will not be required soon to feed the family or host a scrabble game. Ideally a large table with a neutral light gray top, in your own little corner will provide the support and isolation needed to focus on your kit. Try to locate your kit building bench on a linoleum or hardwood floored area. If you must use an area with a wool carpet be aware you will be working bare footed to try to minimize static electricity. . .  . and finding SMD components on a carpet has odds equivalent to hitting 10 the hard way. I’m not saying it can’t be done (I have wool carpeting in my kit building area), but if given a choice, choose the best environment you can.

Now we have a gray table on a linoleum floor in a room with ventilation and light. A window is a good thing as you can’t beat daylight and the ability to force ventilate when the soldering iron is rested on a piece of rubber. I like to ground my workbench (frame of the gray table), to allow me to touch the grounded area before beginning any kind of work each time I return to the building area. Note that the top of the table or bench is usually a non conductor. This helps to minimize risk during power on testing of unenclosed circuit boards. Add a lamp equipped magnifying glass on a boom to help you see those small parts. The one I have has a 120VAC power receptacle to plug the soldering iron into.

Let’s put together some tools for kit building. My kit consists of three sizes of flat bladed and Phillips screwdrivers, a good knife, scissors, three sizes of channel lock pliers, two sizes of vise grips, needle nose pliers, two sizes of adjustable wrenches (the ones with the knurled screw), Qtips, toothpicks, small files, one medium multipurpose file, small magnet on a stick, superglue, gorilla glue, black plastic electrical tape, a wire stripper, an Amp crimp tool (e.g. Super Champ III) that will be your back up wire cutter, stripper, and screw shortener, medium lineman’s pliers, a good pair of flush cutting wire cutters (flag down the Snap On man and ask for 6″ flush wire cutters. . . bring lots of money), and a 8″ pair of heavy duty wire cutters for larger/rougher cuts, Sharpie pen, drill set punch (the kind the fire department uses to break car windows), battery powered drill and a selection of bits, nut driver set, eyeglass  screwdriver set, tape and fixed measures, plastic ferrite core tweakers, hemostats, tweezers, and a case to put all this in. You will undoubtedly find other tools to add to your collection and you can get away with less but this would get you going and avoid trips to Sears during your kit build.

It is best to have your tool kit close by but not on the work bench. I use a small end table to locate the tools next to me and in reach but not on the work surface. So what will we put on the work surface? Let’s start out with a multimeter. Fluke 77 series meters are available cheaply enough but you can use any meter that will allow you to measure voltage, current, and resistance. It could be anything from the venerable Simpson 260 to the $5 digital meters available at your local auto parts shop. A 13.8VDC power supply capable of 20A is a good idea though you could get away with a battery or less current capacity. Since we are building radio related equipment for the most part a dummy load and a Bird 43 or some other kind of Wattmeter and a signal generator may be helpful. A plug strip on the back edge of your work bench will provide AC power to your test gear.

You probably noticed that no mention was made of a soldering iron. That is because this piece of equipment is so important is needs its own paragraph: We will be working with surface mount components so your Weller two position 150/300W gun won’t do. Neither will that monster you used for stained glass or joining double ought cables. OK that was a bit over the top, but it gets extreme on the other side too. There are special and costly RF heat generating solder stations that I do not recommend either. Let’s face it we are working with components that are meant to handle RF so it just doesn’t make sense to me to be applying RF to the input of a delicate component.  I prefer a Weller soldering station with temperature control and display. Mine is an EC 2000 but any soldering station you can set at 700 degrees and get appropriate sized tips for will do. I use a chisel tip that is about as big at the end as the smallest component contact we will be soldering. That’s about 1/16″. Add a second chisel tip that is about 1/4″ at the end for those heavier soldering tasks (like a SO-239 center contact). You will need two rolls of solder; The small size is 0.015 diameter 63Sn/37Pb P2 flux core and the larger is 0.05 diameter 60/40 rosin core. I don’t use lead free solder. Soldering paste is rarely required. You will know when you need it but it generally makes more of a mess than aiding the soldering process. Some find Soldering paste (very miniscule amount) comes in handy to stick a component in place prior to holding it in place with a toothpick while soldering. If you must use soldering paste get the acid free variety and clean it off your work ASAP.

OK, we have a place to work, tools, instruments, a soldering station, and supplies. We are all dressed up and ready to roll. We should pick a kit to build but I’m going to give you a week to get your gear together. The w7bas 222 transverter kit is the most likely suspect at this time. . . . and it might be fun to build yours while I build my second one of these kits.